[PATCH net-next v16 0/6] net: dsa: mxl862xx: devlink flash and rescue

[PATCH net-next v16 0/6] net: dsa: mxl862xx: devlink flash and rescue

[Daniel Golle]

This series adds "devlink dev flash" and "devlink dev info" support to
the MaxLinear MxL862xx DSA driver, and makes a switch stuck in its
MCUboot loader recoverable through the same path.

The switch is flashed over the loader's clause-22 SMDIO download
interface after the firmware API has rebooted it into MCUboot, and the
driver reinitialises through a deferred detach and re-probe once the
new image runs. A switch found in MCUboot at probe registers in a
reduced rescue mode with firmware version 0.0.0, so the same flash flow
recovers it; an interrupted download is drained in the background
first. The deferred re-probe comes from a new driver-core helper,
device_schedule_reprobe(), since a driver-owned work item cannot
survive a racing rmmod, nor give up its detach once the core has
blocked probing for a shutdown. fwupd's devlink plugin carries the
matching quirks [17].

Patch 3 is a driver-core change and patch 4 does not link without it,
so the series needs a driver-core ack before net-next can take it.

Tested on an MxL86252C switch of the BananaPi R4 Pro 8X: an upgrade
through fwupd; a reboot issued while a flash was running, which waits
for the transfer to finish; a host crash mid-transfer, whose wedged
download the background drain recovered; and a power cut mid-transfer,
after which the loader came up ready and fwupd flashed the switch from
0.0.0 back to a released firmware.

Changes since v15 [20]:
 - patch 1: the commit message no longer puts a notification pair
   around a missing firmware file; the core fails that before the pair,
   which wraps the call into the trampoline only
 - patch 3: take no lock in the caller's context and drop the parent
   snapshot, refusing buses that need the parent lock instead. The
   caller-context device lock inverted against the devlink instance
   lock, which a flash holds across the call, and against the
   synchronous cancel of the rescue self-heal work; a pinned parent can
   also be freed by device_move(). Only usb_bus_type sets
   need_parent_lock, and the conversions posted separately re-probe PCI
   and serdev devices, so none of them is refused. Patches 4 and 5 need
   no change of their own for either inversion (all found by Sashiko AI
   review)
 - patch 3: abandon the release when probing gets blocked while
   __device_release_driver() has the locks dropped to unbind busy
   consumer links, closing the one window where a ->remove() could
   follow a ->shutdown(). Earlier versions called it pre-existing, which
   it is, but a deferred re-probe is the one unbind that may be
   abandoned, so it takes a flag the other callers do not (found by
   Sashiko AI review)
 - patch 3: the commit message now describes what this patch changes
   rather than bugs in the drivers it does not convert (found by Sashiko
   AI review)
 - patch 3: the commit message no longer claims the detach is
   synchronised with device_shutdown() in every case. Probing is
   blocked only once wait_for_device_probe() has returned, so a
   re-probe already past the check detaches the device, which then runs
   ->remove() in place of ->shutdown()
 - patch 4: a firmware write blocked by a running flash reports success
   instead of -EBUSY. Tearing a bridge down over a flash, as a reboot
   does, made port_vlan_del() fail; the bridge then leaves the VLAN on
   its list and __vlan_group_free() warns and frees the group with the
   entries still linked
 - patch 4: ->shutdown() now waits for a flash in flight and refuses
   one requested after it, so a reboot cannot cut the image in half.
   The devlink core already serialises .remove() through the instance
   lock; ->shutdown() does not go through devlink and takes that lock
   itself
 - patch 4: the -EBUSY extack of a pending reprobe states a fact rather
   than advising a retry, and the comment on mxl862xx_read_chip_id()
   drops the rescue-mode cache that only patch 5 creates
 - patch 4: select CRC32, which nothing else selects for the image
   checksum validation (found by Sashiko AI review)
 - patch 5: treat a byte count outliving the settle step as a busy
   loader and wait out an erase a dead session left running before
   draining, so a host that died during the loader's erase no longer
   fails probe with the -ETIMEDOUT this series exists to avoid; drop the
   loader's clean ready state with the cached identity when a flash
   fails; state facts only in the extack of a failed recovery (all found
   by Sashiko AI review)
 - patch 5: the commit message and the comments no longer say the
   clause-45 API floods the log with CRC errors when no firmware
   answers. The mailbox commands run into their timeouts instead, and
   testing the stuck-in-MCUboot paths produces no such message; what
   probing SB PDI first saves is the ten seconds of polling and the
   -ETIMEDOUT that ends probe
 - patch 5: move the rescue branch of mxl862xx_setup() into a function
   of its own, which brings its messages back inside 100 columns; state
   a fact in the -EBUSY extack of a running recovery; trim the drain
   comment, whose protocol detail is in the file header, and order its
   declarations
 - patch 6: document that the ports come back down, which recovery
   failure needs a power cycle and which a rebind, and what a re-probe
   that cannot be scheduled leaves behind (found by Sashiko AI review)
 - patch 6: document that a reboot waits for a running flash, that a
   flash requested after it is refused, and that a bus error ends the
   download recovery for good; title-case the "Flash Update" heading
   like the other devlink driver documents
 - Andrew's Reviewed-by is kept on patches 1, 2 and 6: patch 1 gained
   commit message text only and patch 6 the documentation sentences
   above. It is dropped on patch 4, which gained the shutdown
   serialisation
 - patch 3 has drawn no driver-core reply here or in its three
   standalone postings [11][14]. The helper is no longer an RFC: Hans
   de Goede reviewed and tested it there [15][16], and the conversions
   of the open-coded users in iwlwifi, hci_h5 and btintel_pcie follow
   once this series is merged
 - the remaining findings of that review are not acted on: patch 1 is
   asked once more to install .flash_update only for drivers
   implementing the callback, as v4 did, and stays unconditional as
   Andrew asked in v9; the empty supported_interfaces a rescue-mode
   probe leaves for the quad-mode sub-interfaces can only reach phylink
   through a CPU port on one of them, which the chip does not support;
   and the driver pointer patch 3 records could in theory match a
   different driver loaded at the same address within the delay, at the
   cost of one spurious re-probe
 - the changes to patches 1 and 3 to 6, the commit message of patch 1
   included, were written with an LLM coding assistant working from the
   Sashiko findings and from a local review of the posted series, and
   reviewed by hand; the Assisted-by tags on patches 3 to 6 record this

Changes since v14 [19]:
 - patch 3: skip the detach while probing is blocked, which
   device_shutdown() does before its walk reaches any device, instead of
   a per-device flag set only once the walk arrives; validate the device
   and snapshot the parent, its locking requirement and the bound driver
   under the device lock; keep -EPROBE_DEFER out of the re-probe error
   path so it cannot overwrite a deferred probe reason (all found by
   Sashiko AI review)
 - patch 4: treat the closing END write as advisory, since the loader
   has verified the image by then, and admit only the flash task's own
   firmware reads past block_host instead of every read from every
   context (found by Sashiko AI review)
 - patch 5: classify a status register left in the download handshake as
   a loader needing a power cycle rather than as running firmware, give
   the loader one step to publish its next state before ruling it out
   after a failed clause-45 wait, abort the drain polls as soon as
   teardown asks for it instead of stalling unbind for up to 17 s, and
   pair the rescue_mode accesses with WRITE_ONCE()/READ_ONCE() (all
   found by Sashiko AI review)
 - patch 6: asic.rev comes from the CHIP ID registers as well, and -EIO
   means the driver gave up on the recovery, which may need a rebind
   rather than a power cycle (found by Sashiko AI review)
 - Andrew's Reviewed-by is kept on patches 1, 2, 4 and 6; the changes to
   4 and 6 are the two small ones above and a documentation reword
 - the same review asks again whether patch 1 should install
   .flash_update only for drivers implementing the callback, as v4 did;
   it stays unconditional as Andrew asked in v9. Its remaining findings
   are not acted on either: the pre-existing window in
   __device_release_driver() where a ->shutdown() can interleave with a
   release, which every unbind path shares; the recorded driver pointer,
   which an unbind and rebind within the delay can match again at the
   cost of one spurious re-probe; and the get_stats64() re-arm race in
   remove(), which predates this series and is fixed separately for net
 - the changes to patches 3 to 6 were written with an LLM coding
   assistant working from the Sashiko findings and reviewed by hand; the
   Assisted-by tags on those patches record this

Changes since v13 [18]:
 - patch 5: initialise the SerDes state once mxl862xx_wait_ready() has
   cached the firmware version, still before the rescue-mode early
   return, so PCS setup can depend on the running firmware
 - picked up Andrew's Reviewed-by on patches 1 and 4; the one on patch 5
   is not carried as that patch changed
 - the Sashiko review of v13 repeats the ABA finding on patch 3 dismissed
   in v13 and marks the two __device_release_driver() windows and the
   get_stats64() re-arm race as pre-existing; no change
 - the change to patch 5 was written with an LLM coding assistant
   working from a report against a downstream tree and reviewed by
   hand; the Assisted-by tag on that patch records this

Changes since v12 [13]:
 - v12 went out just as net-next closed for the 7.3 merge window. The
   helper of patch 3 was then posted on its own, with conversions of the
   existing open-coded users in iwlwifi, hci_h5 and btintel_pcie, most
   recently as v3 [14], which Greg's patch bot deferred past the merge
   window; Hans de Goede reviewed and tested the helper and the hci_h5
   conversion there on RTL8723BS hardware [15][16]. The Sashiko review
   of that posting found the same issues in the helper as the review of
   v12 did, so patch 3 here supersedes the helper patch of that series;
   once this series is merged, the conversions follow as patches for
   bluetooth-next and wireless-next. On the userspace side, fwupd's
   devlink plugin has meanwhile gained the quirks for these switches
   [17]
 - patch 3: queue the re-probe on system_freezable_wq, so one pending
   across system suspend runs after resume instead of detaching a
   suspended device or racing its late suspend callbacks; record at
   scheduling time whether the parent needs locking instead of reading
   dev->bus, which may be gone with its module once the device was
   unregistered; let __device_release_driver() report whether it
   released the driver, so an administrative unbind that wins the race
   inside the device links loop is not undone by the re-attach (all
   found by Sashiko AI review); use dev_err_probe() for the re-probe
   error path (Hans de Goede)
 - patch 4: stop the stats poll with disable_delayed_work_sync() in the
   flash path, so a racing get_stats64() re-arm is a no-op, and drop the
   early return in the work function; the v12 reordering of remove()
   is gone as well, since the get_stats64() race it addressed predates
   this series and needs a fix of its own (found by Sashiko AI review)
 - two further findings of the same review are not acted on: the
   recorded driver pointer could in theory match a different driver
   loaded at the same address within the delay, which would cost that
   driver one spurious detach and re-probe; and the final put_device()
   from the work could call a release() whose module was unloaded in
   the meantime, which is the same hazard every asynchronous device
   reference in the core carries, the async probe helper included
 - the changes to patches 3 and 4 were written with an LLM coding
   assistant working from the Sashiko findings and reviewed by hand; the
   Assisted-by tags on those two patches record this

Changes since v11 [12]:
 - patch 3: pin the parent device across the deferred re-probe and take
   the parent lock across device_attach() on buses that need it; a
   reference on the child alone left a freed dev->parent dereferenced
   under __device_driver_lock() (found by Sashiko AI review)
 - patch 4: cancel the stats poll after dsa_unregister_switch() so a
   racing get_stats64() cannot re-arm it against freed priv; and keep
   the host blocked for writes across the post-flash readiness poll,
   letting only the flash path's own reads reach the new firmware
   (found by Sashiko AI review)

Changes since v10 [10]:
 - new patch 3: driver core: add device_schedule_reprobe(), as posted
   in the RFC [11], used to schedule the post-flash and post-drain re-probe with
   device_schedule_reprobe() instead of a driver-owned work item.
 - the dsa_switch allocation returns to devres. Keeping it out of
   devres only defused the remaining check-vs-detach window, which the
   core helper closes outright
 - scheduling the re-probe is now the one step that can fail after the
   switch was flashed, since the helper allocates its work item
   internally and v10's allocate-up-front dance is no longer possible.
   An -ENOMEM there is a system-wide condition no driver-level message
   or recovery improves, so flash_update just returns it (unbind and
   rebind reinitialises the driver), and a drain whose hand-off fails
   still marks recovery failed so devlink does not keep promising a
   retry

Changes since v9 [9]:
 - Harmonised the SB PDI timeouts. The verify wait is now one constant
   shared by the flash and drain paths (15 s), the 1-byte mailbox step
   is another (2 s) used by the drain and by both detection waits, and
   the per-slice write budget drops from 120 s to 60 s. The last-slice
   flush, which cannot see the boundary between programming and
   verifying, gets the sum of the two.
 - The post-flash and post-drain reprobe no longer detaches a device
   that has been shut down or unbound, and the dsa_switch is allocated
   outside devres so a lost race cannot leave dsa_switch_find() reading
   freed memory. This was a live bug in v9's patch 3 as well, reachable
   by rebooting within 500 ms of a flash.
 - A failed reprobe hand-off after a successful drain now logs and
   fails flashing outright, instead of leaving devlink answering "retry
   shortly" for good. Dropped heal_lock and mxl862xx_stop_work() with
   it: the lock only made the flag test and the queueing atomic, which
   is not the guarantee the comment claimed, and the reprobe's own
   check is what actually decides now.
 - A loader that publishes READY but never services the register-read
   challenge now reports -ENXIO rather than propagating -ETIMEDOUT, and
   the documented return sets of mxl862xx_rescue_mode_detect() and
   mxl862xx_rescue_drain_finish() match what the code returns.
 - Commit message for patch 4 no longer claims a running firmware is
   "left untouched" (the presence probe writes two mailbox scratch
   registers, inert to a firmware that does not read them), says that
   an SB PDI window away from the OTP reset offsets also yields
   -ENODEV, and describes the -ENXIO outcome above.
 - Commented why STAT == 0 during a drain is unambiguous: by the
   r_remain == 0 rule the loader cannot be both inside the receive loop
   asking for a chunk and publishing a verdict.
 - Documented that a switch power cycled on its own needs the driver
   unbound and rebound before a failed recovery is re-examined.

Changes since v8 [8]:
 - install the flash_update devlink op unconditionally and return
   -EOPNOTSUPP from the trampoline for drivers without the callback,
   instead of a second devlink_ops permutation (Andrew Lunn)
 - picked up Andrew's Reviewed-by on patches 2 and 5, given on v5

Changes since v7 [7]:
 - most of the changes below address findings of the Sashiko AI reviews
   of v7
 - the MCUboot loader's transfer completion was reverse-engineered to
   settle two of them: it publishes an image verification verdict in its
   status register, finalises without the END magic once a 2 s timeout
   expires, and keeps the host's byte count visible while it programs a
   chunk. The interrupted-download drain therefore no longer sends END,
   which a loader still in its receive loop consumes as a byte count and
   underflows its receive counter on, and the flash path now reports a
   rejected image instead of a write timeout
 - refuse a second devlink dev flash while the previous one's reprobe is
   still pending, and stop publishing a zeroed firmware version after a
   failed transfer
 - initialise the SerDes state before the rescue-mode early return, so a
   successful rescue-mode flash cannot hand phylink an unconfigured PCS
 - do not fail probe from the wedged-download branch of the rescue
   detection, which a download interrupted with exactly one byte
   outstanding would trigger, and report a failed recovery through
   devlink rather than refusing every flash for good
 - reset the SB PDI mailbox before probing it, log the drain's progress,
   and correct the protocol and register comments throughout

Changes since v6 [6]:
 - reprobe from a single delayed work item instead of a kthread spawned
   by a workqueue kickoff; the kthread existed only to drop the module
   reference from core code, but its creation-failure path did the racy
   module_put() from module text anyway and could strand the driver
   bound with skip_teardown set. The collapsed form matches
   iwl_trans_reprobe_wk(), and a failed reprobe now leaves the device
   unbound like a failed probe
 - only signal END on a successful transfer; a failure leaves the loader
   mid-payload, where END is read as a byte count and can underflow the
   receive counter, so return the error and let the reprobe recover
 - add cond_resched() to the payload loop so a long transfer over a
   bit-banged MDIO bus under CONFIG_PREEMPT_NONE does not trip the
   soft-lockup detector
 - drop the cached firmware version and chip id on a failed flash so
   devlink dev info stops reporting the pre-flash version until the
   reprobe
 - report the firmware version under DEVLINK_INFO_VERSION_GENERIC_FW
   instead of a bare "fw" string
 - correct the SB PDI header comment's SMDIO register map and expand the
   note on why closing the shared conduit is safe

Changes since v5 [5]:
 - run the post-flash reprobe from a kthread that drops the module
   reference with module_put_and_kthread_exit() from core code, fixing
   a use-after-free where a work item's trailing module_put() could
   return into module text a racing rmmod had freed; a workqueue kickoff
   spawns the kthread off the devlink caller where kthread_create() can
   return -EINTR
 - send END on every flash failure from the ready handshake onward so an
   aborted transfer lets MCUboot reboot instead of leaving it waiting
 - after the background drain finalises an interrupted download, reprobe
   and let the probe-time detection re-classify the switch, so a valid
   image a last-moment interruption left bootable comes up as running
   firmware; rescue_drain() no longer inspects or reports the outcome
 - re-read the SB PDI status register once more after a poll timeout
   expires, so a preempted poll cannot report a spurious -ETIMEDOUT
 - bail out of the periodic stats poll when the flash teardown has set
   WORK_STOPPED, closing a get_stats64() re-arm race
 - allocate the reprobe kickoff before disturbing the switch, so an
   -ENOMEM cannot leave it flashed but never reprobed
 - omit asic.id/asic.rev when the CHIP ID read returned 0, instead of
   publishing a bogus "0000" for fwupd to match firmware against
 - treat the flashless-download loop (STAT 0xc33c) as an unsupported
   configuration and fail probe with -ENODEV instead of advertising it
   as flashable

Changes since v4 [4]:
 - report the numeric chip part number and version read from the
   static CHIP ID registers as the "asic.id" and "asic.rev" fixed
   versions instead of a model-name string, which does not belong in
   a devlink version identifier (Jakub Kicinski)
 - report the running firmware version as the "stored" version too,
   since the switch boots it from its own flash, so userspace can
   distinguish a flash-backed part from a flashless one by the
   presence of "stored" without a future API change
 - run the post-flash reprobe from a self-contained work item again
   instead of the v4 kernel thread, which tripped the hung-task
   watchdog while parked across the flash and returned -EINTR from
   kthread_create() when the devlink command was interrupted
 - re-read the new firmware version through the reprobe's fresh probe
   and drop the SYS_MISC_FW_VERSION exemption from the host block
 - raise the firmware command poll timeout so the FW_UPDATE command
   that reboots into MCUboot is not cut short
 - detect the switch state from the value MCUboot publishes in the SB
   PDI STAT register (loader ready, wedged download, or running
   firmware), confirming a live console loader with a register-read
   challenge, instead of trusting a bare SMDIO scratch write
 - fail probe with -ENODEV over SB PDI when the switch does not respond
   at all (absent, unpowered, or misdescribed in the device tree)
   instead of letting the clause-45 API flood the log with CRC errors
 - drain a wedged interrupted download back to a clean ready state
   from a background work item so the multi-minute recovery never
   holds the devlink instance lock, reporting no firmware version and
   refusing flash with -EBUSY until it completes
 - report the rescue-mode null firmware version "0.0.0" as both the
   running and stored version, matching the running/stored reporting
   above
 - split the devlink documentation into its own patch and add
   Documentation/networking/devlink/mxl862xx.rst describing the info
   versions and the flash update behaviour (Jakub Kicinski)
 - include example "devlink dev info" outputs in the commit messages
   of patches 3 and 4 (Jakub Kicinski)

Changes since v3 [3]:
 - only install the flash_update devlink op for switches whose
   driver implements it, so the devlink core rejects unsupported
   requests before fetching the firmware file from userspace
 - run the deferred reprobe from a kernel thread which ends in
   module_put_and_kthread_exit() instead of a work item that
   dropped its module reference while still executing module code
 - fail firmware API read commands with -ENODEV after the update
   has finished instead of faking success with an unfilled buffer,
   which could send port_fdb_dump() into an endless loop
 - keep the host block in place across the post-update version
   query by exempting SYS_MISC_FW_VERSION from block_host instead
   of briefly lifting the block, and write all blocking flags under
   the MDIO bus lock
 - check the return value of all SB PDI control writes; a failed
   address write during the half-bank switch could otherwise place
   the second half of the payload at the wrong flash offset
 - initialise the progress notification deadline from jiffies so
   notifications are not suppressed on 32-bit systems shortly
   after boot
 - log a distinct diagnostic when rescue mode detection fails on an
   SMDIO bus error instead of silently treating it as not being in
   rescue mode
 - flush the switchdev deferred queue after closing the ports so
   the bridge's deferred STP DISABLED transitions reach the
   firmware while it is still running instead of failing against
   the host block with "failed to set STP state" errors
 - treat -ENODEV as successful deletion in port_mdb_del() so the
   post-update teardown no longer leaves host MDB entries behind
   for the DSA core to report when the tree is torn down

Changes since v2 [2]:
 - validate the firmware image, including both CRCs, before taking
   down any ports, so that a malformed file is rejected without
   disturbing the running switch and without the needless flash and
   reprobe cycle it previously triggered
 - reject images whose declared payload sizes overflow when summed
   (check_add_overflow) or sum up to zero; the latter previously
   erased the flash without writing anything back
 - allocate the reprobe work item and take the module and device
   references before starting the update, so scheduling the reprobe
   can no longer fail after the switch has been pushed into MCUboot
 - prevent the stats poll work from being re-armed and cancel the
   CRC error work before starting the transfer
 - check the host-blocking flags in mxl862xx_api_wrap() under the
   MDIO bus lock to close the race window where an API command
   which had already passed the check could reach the bus after the
   switch rebooted into MCUboot
 - check the return value of SB PDI data word writes so a failed
   MDIO transaction aborts the transfer instead of being noticed
   only through a corrupted image
 - report a per-model chip name (e.g. "MaxLinear MxL86252") as the
   devlink "asic.id" fixed version instead of the devicetree
   compatible string, whose comma is awkward for userspace
   consumers such as fwupd (see discussion on v2 patch 3)
 - report the canonical null version "0.0.0" instead of
   "mcuboot-rescue" as the running firmware version in rescue mode,
   so that version-comparing update tools like fwupd treat every
   available release as an upgrade and offer it for recovery

Changes since RFC [1]:
 - detect a switch stuck in MCUboot rescue mode at probe, register
   the switch without any ports and report "mcuboot-rescue" as the
   running firmware version, so devlink flash can recover from a
   failed or interrupted update (Andrew Lunn)
 - clarify in the commit message of patch 2 that the per-transaction
   MDIO bus locking is about other, non-switch devices on the same
   MDIO bus (Andrew Lunn)
 - mention in the commit message of patch 3 that closing the ports
   also stops phylib from polling the switch-internal PHYs during
   the transfer (Andrew Lunn)
 - split up run-on sentence and explain the dynamically allocated
   reprobe work item instead of just pointing at iwlwifi in the
   commit message of patch 3 (Manuel Ebner)
 - use kzalloc_obj() (Manuel Ebner)
 - state the actual duration of a complete flash and reprobe cycle
   (just under a minute) in comments and the commit message, and
   clarify that the timeout values are generous upper bounds
   (Manuel Ebner)

[1] https://lore.kernel.org/all/ak0J-HgzMRea53om@makrotopia.org/
[2] https://lore.kernel.org/all/cover.1783988826.git.daniel@makrotopia.org/
[3] https://lore.kernel.org/all/cover.1784513694.git.daniel@makrotopia.org/
[4] https://lore.kernel.org/all/cover.1784665017.git.daniel@makrotopia.org/
[5] https://lore.kernel.org/all/cover.1784945329.git.daniel@makrotopia.org/
[6] https://lore.kernel.org/all/cover.1785119999.git.daniel@makrotopia.org/
[7] https://lore.kernel.org/all/cover.1785274610.git.daniel@makrotopia.org/
[8] https://lore.kernel.org/all/cover.1785389905.git.daniel@makrotopia.org/
[9] https://lore.kernel.org/all/cover.1785728574.git.daniel@makrotopia.org/
[10] https://lore.kernel.org/all/cover.1786294649.git.daniel@makrotopia.org/
[11] https://lore.kernel.org/all/anpxFdwNxk0XwPjQ@makrotopia.org/
[12] https://lore.kernel.org/all/cover.1786773971.git.daniel@makrotopia.org/
[13] https://lore.kernel.org/all/cover.1786922210.git.daniel@makrotopia.org/
[14] https://lore.kernel.org/all/cover.1787281239.git.daniel@makrotopia.org/
[15] https://lore.kernel.org/all/c461462f-de0b-43e8-ac9e-541013f5f8da@oss.qualcomm.com/
[16] https://lore.kernel.org/all/7ffe0c2e-0742-488a-ab6c-1dc2fabc049c@oss.qualcomm.com/
[17] https://github.com/fwupd/fwupd/commit/e50c9e5ab39d31242e664efbbf441fd46d15a0cd
[18] https://lore.kernel.org/all/cover.1788783126.git.daniel@makrotopia.org/
[19] https://lore.kernel.org/all/cover.1788976064.git.daniel@makrotopia.org/
[20] https://lore.kernel.org/all/cover.1789175618.git.daniel@makrotopia.org/

Daniel Golle (6):
  net: dsa: add devlink flash_update callback to dsa_switch_ops
  net: dsa: mxl862xx: add SMDIO clause-22 register access
  driver core: add device_schedule_reprobe()
  net: dsa: mxl862xx: add devlink flash_update and info_get
  net: dsa: mxl862xx: recover switch stuck in MCUboot rescue mode
  net: dsa: mxl862xx: document devlink flash and info support

 Documentation/networking/devlink/index.rst    |    1 +
 Documentation/networking/devlink/mxl862xx.rst |   91 ++
 MAINTAINERS                                   |    1 +
 drivers/base/dd.c                             |  111 +-
 drivers/net/dsa/mxl862xx/Kconfig              |    1 +
 drivers/net/dsa/mxl862xx/Makefile             |    2 +-
 drivers/net/dsa/mxl862xx/mxl862xx-api.h       |   10 +
 drivers/net/dsa/mxl862xx/mxl862xx-cmd.h       |    2 +
 drivers/net/dsa/mxl862xx/mxl862xx-fw.c        | 1135 +++++++++++++++++
 drivers/net/dsa/mxl862xx/mxl862xx-fw.h        |   21 +
 drivers/net/dsa/mxl862xx/mxl862xx-host.c      |   68 +
 drivers/net/dsa/mxl862xx/mxl862xx-host.h      |    2 +
 drivers/net/dsa/mxl862xx/mxl862xx-phylink.c   |    2 +
 drivers/net/dsa/mxl862xx/mxl862xx.c           |  165 ++-
 drivers/net/dsa/mxl862xx/mxl862xx.h           |   41 +
 include/linux/device.h                        |    2 +
 include/net/dsa.h                             |    3 +
 net/dsa/devlink.c                             |   13 +
 18 files changed, 1653 insertions(+), 18 deletions(-)
 create mode 100644 Documentation/networking/devlink/mxl862xx.rst
 create mode 100644 drivers/net/dsa/mxl862xx/mxl862xx-fw.c
 create mode 100644 drivers/net/dsa/mxl862xx/mxl862xx-fw.h


base-commit: 1142eb185b05db61a78130890fc4ed268f4cb4e6
prerequisite-patch-id: 0000000000000000000000000000000000000000
-- 
2.55.0

[PATCH net-next v16 1/6] net: dsa: add devlink flash_update callback to dsa_switch_ops

[Daniel Golle]

Add a devlink_flash_update callback to dsa_switch_ops so that DSA
drivers can support devlink dev flash without open-coding the devlink
plumbing. Like the other trampolines in net/dsa/devlink.c, the op
returns -EOPNOTSUPP when the driver does not implement the callback.
The devlink core takes a non-NULL ops->flash_update as the capability
gate, so on a switch without the callback a flash request now fetches
the firmware file first: a missing file fails with -ENOENT instead of
-EOPNOTSUPP, and a file that is found reaches the trampoline inside a
FLASH_UPDATE/FLASH_UPDATE_END notification pair. Both are acceptable
for an operation as infrequent as a firmware update.

The devlink core calls the op with the devlink instance lock held and
without rtnl_lock, whereas DSA serialises its switch and port ops
under rtnl_lock, so a driver has to serialise a flash against its own
ops itself.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
v16:
 - commit message: name the errno and the notifications the shared ops
   table changes for switches without the callback (found by Sashiko
   AI review)
 - commit message: a missing firmware file fails before the
   notification pair, which wraps only the call into the trampoline
v15: no changes
v14: no changes, picked up Andrew's v13 Reviewed-by
v13: no changes
v12: no changes
v11: no changes
v10: no changes
v9: install the flash_update op unconditionally and return -EOPNOTSUPP
    from the trampoline like the other DSA devlink trampolines,
    instead of a second devlink_ops permutation (Andrew Lunn)
v8:
 - retitled: this patch adds the callback, its first user is patch 3
 - describe the op's calling context in the commit message
v7: no changes
v6: no changes
v5: no changes
v4: only install the flash_update op for drivers implementing the
    callback so the devlink core keeps rejecting unsupported flash
    requests before fetching the firmware file
v3: no changes
v2: align continuation lines with the open parenthesis

 include/net/dsa.h |  3 +++
 net/dsa/devlink.c | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 7507d632e7c6..9babab92a0fc 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -1174,6 +1174,9 @@ struct dsa_switch_ops {
 	int	(*devlink_info_get)(struct dsa_switch *ds,
 				    struct devlink_info_req *req,
 				    struct netlink_ext_ack *extack);
+	int	(*devlink_flash_update)(struct dsa_switch *ds,
+					struct devlink_flash_update_params *params,
+					struct netlink_ext_ack *extack);
 	int	(*devlink_sb_pool_get)(struct dsa_switch *ds,
 				       unsigned int sb_index, u16 pool_index,
 				       struct devlink_sb_pool_info *pool_info);
diff --git a/net/dsa/devlink.c b/net/dsa/devlink.c
index ed342f345692..25311a87cbc5 100644
--- a/net/dsa/devlink.c
+++ b/net/dsa/devlink.c
@@ -20,6 +20,18 @@ static int dsa_devlink_info_get(struct devlink *dl,
 	return -EOPNOTSUPP;
 }
 
+static int dsa_devlink_flash_update(struct devlink *dl,
+				    struct devlink_flash_update_params *params,
+				    struct netlink_ext_ack *extack)
+{
+	struct dsa_switch *ds = dsa_devlink_to_ds(dl);
+
+	if (!ds->ops->devlink_flash_update)
+		return -EOPNOTSUPP;
+
+	return ds->ops->devlink_flash_update(ds, params, extack);
+}
+
 static int dsa_devlink_sb_pool_get(struct devlink *dl,
 				   unsigned int sb_index, u16 pool_index,
 				   struct devlink_sb_pool_info *pool_info)
@@ -169,6 +181,7 @@ dsa_devlink_sb_occ_tc_port_bind_get(struct devlink_port *dlp,
 
 static const struct devlink_ops dsa_devlink_ops = {
 	.info_get			= dsa_devlink_info_get,
+	.flash_update			= dsa_devlink_flash_update,
 	.sb_pool_get			= dsa_devlink_sb_pool_get,
 	.sb_pool_set			= dsa_devlink_sb_pool_set,
 	.sb_port_pool_get		= dsa_devlink_sb_port_pool_get,
-- 
2.55.0

[PATCH net-next v16 2/6] net: dsa: mxl862xx: add SMDIO clause-22 register access

[Daniel Golle]

Add mxl862xx_smdio_read() and mxl862xx_smdio_write() for clause-22
SMDIO register access. The switch's MCUboot bootloader exposes only
clause-22 registers; the clause-45 MMD interface needs the running
firmware and is unavailable while the switch is in MCUboot. The MDIO
bus lock is held per-transaction (not across polls) so that SB PDI
polling during flash erase does not starve other non-switch users of
the same MDIO bus, such as separate PHYs providing WAN or management
interfaces.

Unlike mxl862xx_api_wrap(), which takes the bus lock with
MDIO_MUTEX_NESTED because it can be entered from the accessors of
the switch-internal MDIO bus while that bus's lock of the same lock
class is already held, the SMDIO helpers take it with a plain
mutex_lock(). They are only called from probe and devlink flash
contexts where no other MDIO bus lock can be held.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
v16: no changes
v15: no changes
v14: no changes
v13: no changes
v12: no changes
v11: no changes
v10: no changes
v9: no changes, picked up Andrew's v5 Reviewed-by
v8: document the paged register window and the per-transaction bus
    locking next to the helpers, rather than only in this changelog
    (found by Sashiko AI review)
v7: no changes
v6: no changes
v5: no changes
v4: no changes
v3: explain the plain mutex_lock() vs MDIO_MUTEX_NESTED choice in
    the commit message
v2: clarify in the commit message that the per-transaction bus
    locking is about unrelated non-switch devices on the same MDIO
    bus (Andrew Lunn)

 drivers/net/dsa/mxl862xx/mxl862xx-host.c | 40 ++++++++++++++++++++++++
 drivers/net/dsa/mxl862xx/mxl862xx-host.h |  2 ++
 2 files changed, 42 insertions(+)

diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-host.c b/drivers/net/dsa/mxl862xx/mxl862xx-host.c
index 4acd216f7cc0..11759fa6069b 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-host.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-host.c
@@ -495,6 +495,46 @@ int mxl862xx_reset(struct mxl862xx_priv *priv)
 	return ret;
 }
 
+#define MXL862XX_SMDIO_ADDR_REG		0x1f
+#define MXL862XX_SMDIO_PAGE_MASK	0xfff0
+#define MXL862XX_SMDIO_OFF_MASK		0x000f
+
+/* Paged clause-22 window: the page goes into MII register 0x1f, the low nibble
+ * of addr selects one of the 16 registers within it. Both helpers take the MDIO
+ * bus lock per transaction, so callers must not already hold it -- unlike
+ * mxl862xx_api_wrap(), which holds it across a whole firmware command.
+ */
+int mxl862xx_smdio_read(struct mxl862xx_priv *priv, u32 addr)
+{
+	struct mii_bus *bus = priv->mdiodev->bus;
+	int phy = priv->mdiodev->addr;
+	int ret;
+
+	mutex_lock(&bus->mdio_lock);
+	ret = __mdiobus_write(bus, phy, MXL862XX_SMDIO_ADDR_REG,
+			      addr & MXL862XX_SMDIO_PAGE_MASK);
+	if (ret >= 0)
+		ret = __mdiobus_read(bus, phy, addr & MXL862XX_SMDIO_OFF_MASK);
+	mutex_unlock(&bus->mdio_lock);
+	return ret;
+}
+
+int mxl862xx_smdio_write(struct mxl862xx_priv *priv, u32 addr, u16 val)
+{
+	struct mii_bus *bus = priv->mdiodev->bus;
+	int phy = priv->mdiodev->addr;
+	int ret;
+
+	mutex_lock(&bus->mdio_lock);
+	ret = __mdiobus_write(bus, phy, MXL862XX_SMDIO_ADDR_REG,
+			      addr & MXL862XX_SMDIO_PAGE_MASK);
+	if (ret >= 0)
+		ret = __mdiobus_write(bus, phy, addr & MXL862XX_SMDIO_OFF_MASK,
+				      val);
+	mutex_unlock(&bus->mdio_lock);
+	return ret;
+}
+
 void mxl862xx_host_init(struct mxl862xx_priv *priv)
 {
 	INIT_WORK(&priv->crc_err_work, mxl862xx_crc_err_work_fn);
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-host.h b/drivers/net/dsa/mxl862xx/mxl862xx-host.h
index 66d6ae198aff..4e054c6e4c0e 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-host.h
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-host.h
@@ -18,5 +18,7 @@ int mxl862xx_api_wrap(struct mxl862xx_priv *priv, u16 cmd, void *data, u16 size,
 	mxl862xx_api_wrap(dev, cmd, &(data), sizeof((data)), true, true)
 
 int mxl862xx_reset(struct mxl862xx_priv *priv);
+int mxl862xx_smdio_read(struct mxl862xx_priv *priv, u32 addr);
+int mxl862xx_smdio_write(struct mxl862xx_priv *priv, u32 addr, u16 val);
 
 #endif /* __MXL862XX_HOST_H */
-- 
2.55.0

[PATCH net-next v16 3/6] driver core: add device_schedule_reprobe()

[Daniel Golle]

Drivers that need a deferred re-probe of their own device open-code a
work item in module text. iwlwifi (iwl_trans_schedule_reprobe(), for a
firmware crash a lighter restart cannot fix) and hci_h5
(h5_btrtl_resume(), RTL devices lose their firmware state over suspend)
both end that work function with put_device(); kfree();
module_put(THIS_MODULE);, where a concurrent rmmod can free the module
text the epilogue is still executing. Neither checks any bound state
before calling device_reprobe(), and a driver cannot make that check
stick because device_reprobe() takes the device lock internally, so a
stale re-probe undoes an administrative unbind and the detach half runs
against a device whose ->shutdown() has already run.

Add device_schedule_reprobe(), which detaches and re-probes a device
after a caller-specified delay. The work function is built-in text and
the recorded driver pointer is only ever compared, never dereferenced,
so a caller needs no module reference. The bound-state check and
__device_release_driver() run under one hold of the device lock, and
__device_release_driver() now reports whether it was this call that
released the driver, so an unbind winning the race while busy consumer
links are unbound is not followed by a re-attach. The first user is the
mxl862xx devlink flash path added later in this series.

Nothing is locked or validated in the caller's context, so the helper
may be called with the device lock held, as the PM callbacks, ->remove()
and ->shutdown() hold it. Buses that take the parent lock to bind are
refused with -EINVAL: that lock has to be taken before @dev's own, so
the parent would have to be recorded before either is held, where
device_move() can replace it without taking any device lock.
usb_bus_type is the only such bus and no caller needs it today;
supporting one means deriving the parent inside the work and re-checking
it once both locks are held.

The detach is skipped once probing is blocked, which device_shutdown()
and dpm_prepare() both do before they touch any device. dpm_prepare()
leaves no window, its callers having frozen the freezable workqueues
first; device_shutdown() blocks probing only once
wait_for_device_probe() has returned, so a re-probe already past the
test completes its detach and the device runs ->remove() in place of
->shutdown(). __device_release_driver()
drops the device lock while busy consumer links are unbound, which would
let a ->shutdown() interleave in the middle of a release already under
way, so it now re-checks on re-acquisition and abandons the release. That
is offered as a flag, because only a caller free to leave the device
bound can take it: an administrative unbind has to complete, and
driver_detach() would spin on a device it never released. Past that loop
the lock is held until the driver is gone, so ->remove() cannot follow a
->shutdown() on the same device.

Assisted-by: LLM
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
v16:
 - commit message: device_shutdown() blocks probing only once
   wait_for_device_probe() has returned, so a re-probe already past the
   test detaches the device instead of leaving it bound for its
   ->shutdown()
 - take no lock in the caller's context and drop the parent snapshot,
   refusing buses that need the parent lock instead: the caller-context
   device lock inverted against the devlink instance lock on the flash
   path and against a synchronous work cancel on the rescue path, and a
   pinned parent can be freed by device_move() (found by Sashiko AI
   review)
 - abandon the release when probing is blocked while the device links
   loop has the locks dropped, rather than calling that window
   pre-existing: a deferred re-probe is the one unbind that may be
   abandoned, so it is the one that can close it (found by Sashiko AI
   review)
 - commit message: describe what this patch changes rather than bugs in
   drivers it does not convert, and name the first user (found by
   Sashiko AI review)
 - kernel-doc: drop the promise that an administrative unbind always
   wins, which unbind_store() does not guarantee (found by Sashiko AI
   review)

v15:
 - skip the detach while probing is blocked instead of adding a
   per-device shutdown_done flag: device_shutdown() blocks probing
   before its walk starts, so the flag left a window where the work
   detached a device that then neither re-attached nor got its
   ->shutdown() call (found by Sashiko AI review)
 - validate the device and snapshot the parent, its locking requirement
   and the bound driver under the device lock, so an unregister racing
   the allocation can neither leave a freed parent pinned nor pair a
   NULL parent with a request to lock it (found by Sashiko AI review)
 - keep -EPROBE_DEFER out of the re-probe error path, where
   dev_err_probe() would record the message as the device's deferred
   probe reason (found by Sashiko AI review)
 - kernel-doc: a stale re-probe leaves an unbound device unbound, which
   an unbind followed by a rebind within the delay does not (found by
   Sashiko AI review)

v14: no changes

v13:
 - queue the work on system_freezable_wq, so a re-probe pending across
   system suspend can neither detach a device the PM core has suspended
   nor race its late suspend callbacks; it runs after resume instead
   (found by Sashiko AI review)
 - record at scheduling time whether the parent needs locking, instead
   of reading dev->bus in the work, which may be gone with its module
   once the device has been unregistered (found by Sashiko AI review)
 - let __device_release_driver() report whether it released the driver,
   so an administrative unbind that wins the race inside the device
   links loop is not undone by the re-attach (found by Sashiko AI
   review)
 - use dev_err_probe() for the re-probe error path, so a re-probe
   deferred at resume no longer logs a spurious error (Hans de Goede,
   on the standalone posting of this helper)
 - describe the parent pinning and locking in the commit message, as in
   the standalone posting

v12:
 - pin the parent device across the deferred work; a reference on the
   child alone left device_reprobe_work_fn() dereferencing a freed
   dev->parent under __device_driver_lock() when the device was
   unregistered before the work ran (found by Sashiko AI review)
 - take the parent lock across device_attach() on buses that require
   it, matching bus_rescan_devices_helper() (found by Sashiko AI review)

v11: new patch: add device_schedule_reprobe() to the driver core (posted
     earlier as an RFC) so mxl862xx can schedule its post-flash and
     post-drain re-probe through the core instead of open-coding a work
     item

 drivers/base/dd.c      | 111 +++++++++++++++++++++++++++++++++++++++--
 include/linux/device.h |   2 +
 2 files changed, 109 insertions(+), 4 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index f6525a7ee8c5..f521ddefc4a8 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -1314,8 +1314,12 @@ EXPORT_SYMBOL_GPL(driver_attach);
 /*
  * __device_release_driver() must be called with @dev lock held.
  * When called for a USB interface, @dev->parent lock must be held as well.
+ * @abort_if_blocked gives up the release instead when probing has been
+ * blocked while the locks were dropped; only a caller that may abandon
+ * the unbind altogether can ask for it.
  */
-static void __device_release_driver(struct device *dev, struct device *parent)
+static bool __device_release_driver(struct device *dev, struct device *parent,
+				    bool abort_if_blocked)
 {
 	struct device_driver *drv;
 
@@ -1334,9 +1338,10 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 			 * have released the driver successfully while this one
 			 * was waiting, so check for that.
 			 */
-			if (dev->driver != drv) {
+			if (dev->driver != drv ||
+			    (abort_if_blocked && defer_all_probes)) {
 				pm_runtime_put(dev);
-				return;
+				return false;
 			}
 		}
 
@@ -1359,7 +1364,10 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 
 		bus_notify(dev, BUS_NOTIFY_UNBOUND_DRIVER);
 		kobject_uevent(&dev->kobj, KOBJ_UNBIND);
+		return true;
 	}
+
+	return false;
 }
 
 void device_release_driver_internal(struct device *dev,
@@ -1369,7 +1377,7 @@ void device_release_driver_internal(struct device *dev,
 	__device_driver_lock(dev, parent);
 
 	if (!drv || drv == dev->driver)
-		__device_release_driver(dev, parent);
+		__device_release_driver(dev, parent, false);
 
 	__device_driver_unlock(dev, parent);
 }
@@ -1436,3 +1444,98 @@ void driver_detach(const struct device_driver *drv)
 		put_device(dev);
 	}
 }
+
+struct device_reprobe {
+	struct delayed_work work;
+	const struct device_driver *drv;
+	struct device *dev;
+};
+
+static void device_reprobe_work_fn(struct work_struct *work)
+{
+	struct device_reprobe *rp = container_of(work, struct device_reprobe,
+						 work.work);
+	struct device *dev = rp->dev;
+	bool detached = false;
+	int ret;
+
+	device_lock(dev);
+	/*
+	 * rp->drv is only ever compared, never dereferenced: the driver it
+	 * points to may have been unregistered and freed by now.
+	 * device_shutdown() blocks probing before its walk reaches @dev.
+	 */
+	if (!defer_all_probes && !dev->p->dead && dev->driver == rp->drv)
+		detached = __device_release_driver(dev, NULL, true);
+	device_unlock(dev);
+
+	if (detached) {
+		ret = device_attach(dev);
+		if (ret < 0 && ret != -EPROBE_DEFER)
+			dev_err_probe(dev, ret,
+				      "re-probe failed, device left unbound\n");
+	}
+
+	put_device(dev);
+	kfree(rp);
+}
+
+/**
+ * device_schedule_reprobe - schedule a deferred detach and re-probe
+ * @dev: device to detach and re-probe
+ * @delay_ms: delay in milliseconds before the re-probe runs
+ *
+ * Schedule a detach and re-probe of @dev after @delay_ms milliseconds.
+ * The re-probe is skipped if, by the time the scheduled work runs, the
+ * device has been removed, probing has been blocked for a system
+ * shutdown, or @dev is no longer bound to the driver that was bound at
+ * scheduling time.
+ *
+ * The work function is built-in text, so the bound driver may call this
+ * from its own code without holding a module reference. If the driver
+ * module is unloaded before the work runs, driver unregistration unbinds
+ * @dev first and the scheduled work does nothing.
+ *
+ * Multiple pending re-probes for the same device are individually safe;
+ * a caller that wants at most one pending re-probe must gate scheduling
+ * itself.
+ *
+ * The work is freezable: a re-probe pending across system suspend runs
+ * once the system has resumed.
+ *
+ * Nothing is locked in the caller's context, so this may be called from
+ * any process context, @dev's own device lock held included, but not
+ * from @dev's ->probe(), which the scheduled work would detach.
+ *
+ * Returns: 0 on success, -EINVAL if @dev is not a registered device
+ * bound to a driver or sits on a bus which takes the parent lock to
+ * bind, -ENOMEM on allocation failure.
+ */
+int device_schedule_reprobe(struct device *dev, unsigned int delay_ms)
+{
+	const struct device_driver *drv;
+	struct device_reprobe *rp;
+
+	drv = READ_ONCE(dev->driver);
+	/*
+	 * A bus taking the parent lock would need @dev's parent pinned until
+	 * the work runs, which device_move() can invalidate.
+	 */
+	if (!drv || !dev->bus || dev->bus->need_parent_lock || !dev->p ||
+	    dev->p->dead || !device_is_registered(dev))
+		return -EINVAL;
+
+	rp = kzalloc_obj(*rp);
+	if (!rp)
+		return -ENOMEM;
+
+	rp->dev = get_device(dev);
+	rp->drv = drv;
+
+	INIT_DELAYED_WORK(&rp->work, device_reprobe_work_fn);
+	queue_delayed_work(system_freezable_wq, &rp->work,
+			   msecs_to_jiffies(delay_ms));
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(device_schedule_reprobe);
diff --git a/include/linux/device.h b/include/linux/device.h
index aee79fd6b32b..7a9916950577 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1314,6 +1314,8 @@ int  __must_check device_attach(struct device *dev);
 int __must_check driver_attach(const struct device_driver *drv);
 void device_initial_probe(struct device *dev);
 int __must_check device_reprobe(struct device *dev);
+int __must_check device_schedule_reprobe(struct device *dev,
+					 unsigned int delay_ms);
 
 bool device_is_bound(struct device *dev);
 
-- 
2.55.0

[PATCH net-next v16 4/6] net: dsa: mxl862xx: add devlink flash_update and info_get

[Daniel Golle]

Implement runtime firmware upgrade via "devlink dev flash" and version
reporting via "devlink dev info":

  $ devlink dev info mdio_bus/mdio-bus:10
  mdio_bus/mdio-bus:10:
    driver mxl862xx
    versions:
        fixed:
          asic.id 8628
          asic.rev 0
        running:
          fw 1.0.70
        stored:
          fw 1.0.70

The "asic.id" and "asic.rev" fixed versions carry the numeric chip part
number and revision from the static CHIP ID registers (SYS_MISC_REG_RD),
which userspace such as fwupd matches firmware against; they are omitted
if the read fails or the part is unfused, so no bogus "0000" is
published. The switch boots its firmware from its own flash, so "fw" is
reported as both the running and the stored version; a flashless part
would omit "stored", distinguishing the two without an API change.

  $ devlink dev flash mdio_bus/mdio-bus:10 file mxl862xx-fw.bin

The image, including both payload CRCs, is validated first, so a
malformed file is rejected without disturbing the running switch. The
driver then sends SYS_MISC_FW_UPDATE, which reboots the switch into its
MCUboot bootloader, and transfers the signed image over the SB PDI
protocol (clause-22 SMDIO), checking every write: a failed address write
at the half-bank boundary would otherwise misplace half the payload
unnoticed. A successful transfer reboots the switch into the new
firmware. The loader verifies the image once the last slice has been
programmed and publishes the verdict, so a rejected image is reported as
such rather than as a transfer timeout. The whole cycle takes just under
a minute.

For its duration the driver closes all user and conduit interfaces and
marks the user ports not-present with netif_device_detach() so userspace
cannot reopen them; the conduit belongs to the MAC driver and is only
closed. This also stops phylib polling the switch-internal PHYs,
unreachable in MCUboot. The bridge's deferred STP DISABLED transitions
are flushed under rtnl so they reach the firmware while it still runs;
the stats poll and CRC error handler are stopped; and firmware API
commands from other paths are blocked under the MDIO bus lock so none
reaches the bus once the switch has rebooted. A blocked write reports
success: the reprobe discards the switch configuration in any case, and
a bridge removing its ports while the flash runs must not see
port_vlan_del() fail, which leaves its VLAN group non-empty. Progress is
reported through devlink status notifications.

The switch leaves MCUboot on its own by booting the new image, but the
driver has no in-place path back, so it reinitialises with a deferred
re-probe scheduled regardless of the transfer outcome, using
device_schedule_reprobe() from the previous patch. The helper's work
runs in the driver core, off the devlink caller's locking and signal
context, without this driver holding module or device references, and
it skips the re-probe if the device is unbound or shut down before it
fires, so a stale re-probe can neither undo an administrative unbind
nor detach a device whose ->shutdown() has already run. During the
teardown the driver's API reads return -ENODEV and writes fake success,
so it neither stalls on the absent firmware nor consumes buffers it
never filled; port_mdb_del() takes that -ENODEV for a MAC table that is
gone and reports success, since there is nothing left to delete. A
failed re-probe leaves the device unbound, exactly as a failed initial
probe would, and a further flash is refused until it has run. An
aborted transfer leaves the switch in MCUboot, where nothing here can
reach it; the next patch adds the detection that makes such a switch
flashable again.

Scheduling the re-probe can only fail on memory allocation, and only
after the switch has already been flashed. -ENOMEM there is a
system-wide condition that no driver-level message or recovery attempt
improves, so it is returned as-is with no further action: the driver
stays bound with its firmware API short-circuited, and unbinding and
rebinding it runs the same teardown and fresh probe the re-probe would
have.

The closed user ports and conduit are not returned to their pre-flash
administrative state across the reprobe; userspace brings them back up,
and restoring it in-driver would need DSA-core support that does not
yet exist.

A reboot must not cut a transfer in half. The devlink core holds the
instance lock across the whole flash and devlink_unregister() takes the
same lock, so .remove() already waits; ->shutdown() does not go through
devlink at all, and takes the lock itself to wait as well. It also
marks the switch, so a flash arriving once the shutdown has begun is
refused rather than started against a device about to go away.

Assisted-by: LLM
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
v16:
 - report success for a firmware write blocked by a running flash,
   instead of -EBUSY. Tearing a bridge down over a flash made
   port_vlan_del() fail, which leaves the VLAN on the bridge's list:
   __vlan_group_free() then warns and frees the group with the entries
   still linked
 - wait for a flash in flight in ->shutdown() and refuse one requested
   after it, so a reboot no longer cuts the image in half
 - state a fact in the -EBUSY extack of a pending reprobe, dropping the
   retry advice
 - the comment on mxl862xx_read_chip_id() no longer describes a
   rescue-mode cache that only the next patch creates
 - select CRC32, which nothing else selects for the crc32_le() calls
   validating the image checksums (found by Sashiko AI review)
 - Andrew's Reviewed-by is dropped for the ->shutdown() change

v15:
 - treat the closing END write as advisory: the loader has left the
   receive loop and verified the image by then, so a failed write no
   longer reports a completed flash as a transfer failure (found by
   Sashiko AI review)
 - admit only the flash task's own firmware reads past block_host,
   instead of every read from any context, which let ethtool and FDB
   queries reach the freshly booted firmware and left an mdb_add() half
   executed (found by Sashiko AI review)

v14: no changes, picked up Andrew's v13 Reviewed-by

v13: stop the stats poll with disable_delayed_work_sync() in the flash
     path, so a racing get_stats64() re-arm is a no-op, and drop the
     early return in the work function with it; the v12 reordering of
     remove() is gone as well, since the race it addressed predates
     this series and needs a fix of its own (found by Sashiko AI review)

v12:
 - cancel the stats poll after dsa_unregister_switch() in .remove(): a
   get_stats64() past its lockless WORK_STOPPED check could re-arm the
   work after the cancel and then run against the devres-freed priv
   (found by Sashiko AI review)
 - keep block_host set across the post-flash readiness poll and let
   only the flash path's own firmware reads through, so a concurrent
   bridge or STP write cannot reach the freshly booted firmware with
   stale pre-flash resource IDs while rtnl is dropped (found by Sashiko
   AI review)

v11:
 - schedule the post-flash re-probe with device_schedule_reprobe()
   instead of a driver-owned work item; the module and device references
   and the drvdata bound-check go away with it, and with them both
   findings of the v10 AI review -- the work function no longer ends in
   module text behind a module_put(), and the bound-check and detach now
   run under one __device_driver_lock() hold in the core where
   ->shutdown() cannot interleave between them
 - the dsa_switch allocation returns to devres; keeping it out only
   defused the check-vs-detach window that the core helper now closes
   outright
 - scheduling the re-probe is now the one step that can fail after the
   switch was flashed, since the helper allocates its own work item; an
   -ENOMEM there is returned as-is, since unbind and rebind reinitialises
   the driver

v10:
 - do not reprobe a device that has been shut down or unbound. The work
   cannot be cancelled from teardown: .shutdown() runs under
   device_lock(), which device_reprobe() takes as well, so a lock shared
   between the two would deadlock, and cancel_delayed_work_sync() would
   hang on the nested remove() the work triggers itself. It checks
   drvdata under device_lock() instead, which both .shutdown() and the
   driver core clear (found by Sashiko AI review of patch 4, but this is
   where the reprobe comes from)
 - allocate the dsa_switch outside devres and free it in .remove(), so
   losing the remaining race with .shutdown() cannot let devres free it
   while the DSA tree still holds dsa_ports pointing at it
 - lower the per-slice write timeout from 120 s to 60 s, so this path
   and the drain added in patch 4 agree on how long the same loader step
   may take (found by Sashiko AI review)

v9: no changes

v8:
 - refuse a second devlink dev flash while the previous one's reprobe is
   still pending: the firmware API is short-circuited by then, so the
   FW_UPDATE command faked success and the raw SB PDI writes ran against
   a switch the driver no longer tracks (found by Sashiko AI review)
 - omit the firmware version from devlink dev info while the cached copy
   is all-zero, so a failed transfer no longer publishes 0.0.0 as both
   running and stored, and clear asic_rev along with asic_id (found by
   Sashiko AI review)
 - only translate -ENODEV into success in port_mdb_del() during the
   post-flash teardown; outside it, a genuine bus error was reported to
   switchdev as a successful deletion (found by Sashiko AI review)
 - evaluate the image verification verdict the loader publishes after
   the last slice, instead of polling for a value it had already
   published, so a rejected image is no longer reported as a write
   timeout
 - rename the end_magic label to no_end, which is what it does, and
   correct the protocol comment: END is optional as the loader finalises
   on a 2 s timeout, the status register keeps the byte count while a
   chunk is programmed, and the half-bank switch does not clear DATA
   (found by Sashiko AI review)

v7:
 - reprobe from a single delayed work item instead of a kthread spawned
   by a workqueue kickoff; the kthread existed only to drop the module
   reference from core code, but its creation-failure path did the racy
   module_put() from module text anyway and could strand the driver
   bound with skip_teardown set. The collapsed form matches
   iwl_trans_reprobe_wk(), and a failed reprobe now leaves the device
   unbound like a failed probe
 - only signal END on a successful transfer; a failure leaves the loader
   mid-payload, where a STAT write is a byte count and END (0x3cc3) is
   read as one, risking a receive-counter underflow, so return the error
   and let the reprobe recover
 - add cond_resched() to the payload loop so a long transfer over a
   bit-banged MDIO bus under CONFIG_PREEMPT_NONE does not trip the
   soft-lockup detector
 - drop the cached firmware version and chip id on a failed flash so
   devlink dev info stops reporting the pre-flash version until the
   reprobe re-reads it
 - report the firmware version under DEVLINK_INFO_VERSION_GENERIC_FW
   instead of a bare "fw" string
 - correct the SB PDI header comment's SMDIO register map (page in MII
   reg 0x1f, register from the low nibble) and expand the note on why
   closing the shared conduit is safe

v6:
 - confirm the new firmware is running with mxl862xx_wait_ready() and
   lift the host block before reporting success, so devlink dev flash
   completes only once the update has taken effect instead of relying
   on the later reprobe to pick up the new version
 - run the post-flash reprobe from a kthread that drops the module
   reference with module_put_and_kthread_exit(), spawned from a
   workqueue kickoff, closing a use-after-free where a work item's
   trailing module_put() could return into module text a racing rmmod
   had already freed
 - jump to the end_magic teardown on every flash failure from the
   ready handshake onward, so an aborted transfer sends END and lets
   MCUboot reboot instead of leaving the loader waiting
 - poll the SB PDI status register with read_poll_timeout(), which
   evaluates the condition once more after the deadline, so a preempted
   poll cannot report a spurious -ETIMEDOUT
 - bail out of the periodic stats poll when the flash teardown has set
   WORK_STOPPED, closing a get_stats64() re-arm race
 - allocate the reprobe kickoff before disturbing the switch, so an
   -ENOMEM cannot leave it flashed but never reprobed with block_host
   and skip_teardown stuck set
 - omit asic.id/asic.rev when the CHIP ID read returned 0, instead of
   publishing a bogus "0000" for fwupd to match firmware against

v5:
 - report the numeric chip part number and version read from the
   static CHIP ID registers as "asic.id" and "asic.rev" instead of a
   model-name string, which does not belong in a devlink version
   identifier (Jakub Kicinski)
 - report the running firmware version as the "stored" version too,
   since the switch boots it from its own flash, so userspace can
   tell a flash-backed part from a flashless one by the presence of
   "stored" without a future API change
 - run the post-flash reprobe from a self-contained work item again
   instead of the v4 kernel thread, which tripped the hung-task
   watchdog while parked across the flash and returned -EINTR from
   kthread_create() when the devlink command was interrupted
 - re-read the new firmware version through the reprobe's fresh probe
   and drop the SYS_MISC_FW_VERSION exemption from the host block
 - raise the firmware command poll timeout so the FW_UPDATE command
   that reboots into MCUboot is not cut short
 - move the devlink documentation into its own patch

v4:
 - run the deferred reprobe from a kernel thread ending in
   module_put_and_kthread_exit() instead of a work item whose final
   module_put() raced against module unload
 - fail API read commands with -ENODEV after the update instead of
   faking success with an unfilled buffer, which sent
   port_fdb_dump() into an endless loop
 - keep block_host set across the post-update version query by
   exempting SYS_MISC_FW_VERSION instead of briefly lifting the
   block, and write the blocking flags under the MDIO bus lock
 - check the return value of every SB PDI control write; a failed
   address write during the half-bank switch could place the second
   half of the payload at the wrong flash offset undetected
 - report SMDIO write failures through one shared error path instead
   of per-site messages
 - initialise the progress notification deadline from jiffies so
   notifications are not suppressed on 32-bit shortly after boot
 - flush the switchdev deferred queue after closing the ports so the
   bridge's deferred STP DISABLED transitions reach the firmware
   while it is still running instead of failing with -EBUSY against
   the host block
 - treat -ENODEV as successful deletion in port_mdb_del() so the
   post-update teardown does not leave leftover host MDB entries
   behind for the DSA core to report

v3:
 - validate the image, including both CRCs, before closing any ports
   so a malformed file no longer triggers a flash and reprobe cycle
 - reject images whose declared payload sizes overflow when summed
   (check_add_overflow) or sum up to zero; the latter used to erase
   the flash without writing anything back
 - allocate the reprobe work item and take the module and device
   references before disturbing the switch instead of silently
   skipping the reprobe when the allocation fails afterwards
 - check block_host/skip_teardown under the MDIO bus lock to close
   the window where a command already past the check could reach the
   bus after the switch rebooted into MCUboot
 - prevent the stats poll work from being re-armed and cancel the
   CRC error work before the transfer
 - check the return value of SB PDI data word writes; control writes
   are verified by the subsequent status polls
 - report a per-model chip name from the OF match data as "asic.id"
   instead of the devicetree compatible string whose comma is
   awkward for userspace consumers (Andrew Lunn)
 - commit message: the conduit is only closed, not detached

v2:
 - factor out SB PDI slice flush and devlink status notification
   helpers, resolving checkpatch issues
 - use kzalloc_obj() (Manuel Ebner)
 - add kernel-doc for the new mxl862xx_priv members
 - trim comments and state the actual duration of a flash and reprobe
   cycle, just under a minute (Manuel Ebner)
 - reword commit message: split up run-on sentence, explain the
   dynamically allocated reprobe work item (Manuel Ebner), mention
   that closing the ports stops phylib polling (Andrew Lunn)

 drivers/net/dsa/mxl862xx/Kconfig         |   1 +
 drivers/net/dsa/mxl862xx/Makefile        |   2 +-
 drivers/net/dsa/mxl862xx/mxl862xx-api.h  |  10 +
 drivers/net/dsa/mxl862xx/mxl862xx-cmd.h  |   2 +
 drivers/net/dsa/mxl862xx/mxl862xx-fw.c   | 670 +++++++++++++++++++++++
 drivers/net/dsa/mxl862xx/mxl862xx-fw.h   |  18 +
 drivers/net/dsa/mxl862xx/mxl862xx-host.c |  20 +
 drivers/net/dsa/mxl862xx/mxl862xx.c      |  63 ++-
 drivers/net/dsa/mxl862xx/mxl862xx.h      |  21 +
 9 files changed, 805 insertions(+), 2 deletions(-)
 create mode 100644 drivers/net/dsa/mxl862xx/mxl862xx-fw.c
 create mode 100644 drivers/net/dsa/mxl862xx/mxl862xx-fw.h

diff --git a/drivers/net/dsa/mxl862xx/Kconfig b/drivers/net/dsa/mxl862xx/Kconfig
index e51a67a3cf9b..8bb524fe28d1 100644
--- a/drivers/net/dsa/mxl862xx/Kconfig
+++ b/drivers/net/dsa/mxl862xx/Kconfig
@@ -3,6 +3,7 @@ config NET_DSA_MXL862
 	tristate "MaxLinear MxL862xx"
 	depends on NET_DSA
 	select CRC16
+	select CRC32
 	select NET_DSA_TAG_MXL_862XX
 	help
 	  This enables support for the MaxLinear MxL862xx switch family.
diff --git a/drivers/net/dsa/mxl862xx/Makefile b/drivers/net/dsa/mxl862xx/Makefile
index a7be0e6669df..bccac0d0f703 100644
--- a/drivers/net/dsa/mxl862xx/Makefile
+++ b/drivers/net/dsa/mxl862xx/Makefile
@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_NET_DSA_MXL862) += mxl862xx_dsa.o
-mxl862xx_dsa-y := mxl862xx.o mxl862xx-host.o mxl862xx-phylink.o
+mxl862xx_dsa-y := mxl862xx.o mxl862xx-host.o mxl862xx-phylink.o mxl862xx-fw.o
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-api.h b/drivers/net/dsa/mxl862xx/mxl862xx-api.h
index a180a5decffc..6f771895984c 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-api.h
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-api.h
@@ -1224,6 +1224,16 @@ struct mxl862xx_sys_fw_image_version {
 	__le32 iv_build_num;
 } __packed;
 
+/**
+ * struct mxl862xx_sys_reg_rw - System register read/write
+ * @addr: 32-bit register address
+ * @val: register value
+ */
+struct mxl862xx_sys_reg_rw {
+	__le32 addr;
+	__le32 val;
+} __packed;
+
 /**
  * enum mxl862xx_port_type - Port Type
  * @MXL862XX_LOGICAL_PORT: Logical Port
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-cmd.h b/drivers/net/dsa/mxl862xx/mxl862xx-cmd.h
index c87a955c13c4..a865425aa61e 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-cmd.h
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-cmd.h
@@ -70,7 +70,9 @@
 #define INT_GPHY_READ			(GPY_GPY2XX_MAGIC + 0x1)
 #define INT_GPHY_WRITE			(GPY_GPY2XX_MAGIC + 0x2)
 
+#define SYS_MISC_FW_UPDATE		(SYS_MISC_MAGIC + 0x1)
 #define SYS_MISC_FW_VERSION		(SYS_MISC_MAGIC + 0x2)
+#define SYS_MISC_REG_RD			(SYS_MISC_MAGIC + 0x8)
 
 #define MXL862XX_XPCS_PCS_CONFIG	(MXL862XX_XPCS_MAGIC + 0x1)
 #define MXL862XX_XPCS_PCS_GET_STATE	(MXL862XX_XPCS_MAGIC + 0x2)
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-fw.c b/drivers/net/dsa/mxl862xx/mxl862xx-fw.c
new file mode 100644
index 000000000000..139c14adf2d9
--- /dev/null
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-fw.c
@@ -0,0 +1,670 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Firmware flash and devlink support for MaxLinear MxL862xx
+ *
+ * Copyright (C) 2025 Daniel Golle <daniel@makrotopia.org>
+ *
+ * SB PDI - firmware download interface over clause-22 SMDIO
+ * =========================================================
+ *
+ * The MxL862xx MCUboot loader accepts a firmware image through four "SB PDI"
+ * registers in the switch SMDIO register space. It runs whenever no WSP
+ * firmware is active: the normal firmware update enters it deliberately - the
+ * SYS_MISC_FW_UPDATE API command sets a sticky rescue bit and reboots into
+ * MCUboot - and the loader also stays here when the stored WSP firmware fails
+ * its boot-time integrity check. This driver drives the loader's 0xc55c
+ * "console" download path.
+ *
+ * SMDIO register access (mxl862xx_smdio_read/write):
+ *   MII reg 0x1f := (<sb_pdi_reg> & 0xfff0)   ; page latch
+ *   MII reg (<sb_pdi_reg> & 0x000f) := / => <u16 data>
+ * so CTRL/ADDR/DATA/STAT (0xe100..0xe103) are MII regs 0/1/2/3 of page
+ * 0xe100, not all reg 0x00.
+ *
+ * SB PDI registers (host name/addr  ->  MCU mailbox):
+ *   CTRL 0xe100 -> 0xc0938400   mode: RST=0x00  RD=0x01  WR=0x02
+ *   ADDR 0xe101 -> 0xc0938404   SB target word address (SB1 bank = 0x7800)
+ *   DATA 0xe102 -> 0xc0938408   16-bit data / reply word
+ *   STAT 0xe103 -> 0xc093840c   handshake: a magic (below) or a byte count
+ *
+ * STAT magics:
+ *   READY  0xc55c   loader idle in the console loop        (this driver)
+ *   START  0xf48f   host   -> begin download session
+ *   ACK    0xf490   loader -> START acknowledged (START + 1)
+ *   END    0x3cc3   host   -> finalise now (optional, see below)
+ *
+ * Console flash path (STAT=0xc55c) - mxl862xx_flash_firmware():
+ *
+ *   host                                   loader
+ *   ----                                   ------
+ *   reset (CTRL=ADDR=DATA=0)
+ *   read STAT ............................ 0xc55c   (READY, idle)
+ *   STAT := START(0xf48f)  -------------->
+ *                          <-------------- STAT = 0xf490 (ACK)
+ *   CTRL := WR
+ *   DATA := hdr[0..9]  (20-byte header: type,size1,crc1,size2,crc2)
+ *   reset; STAT := 20 (header len)  -----> parse hdr; r_remain=size1+size2;
+ *                                          ERASE target region(s)
+ *                          <-------------- STAT=21 (len+1), then STAT=0
+ *                                          (erased)
+ *   -- payload, streamed in slices: --
+ *   CTRL := WR
+ *   DATA := word x N ...
+ *     at word 16384: CTRL:=RST; ADDR:=0x7800; CTRL:=WR  (half-bank -> SB1)
+ *     at word 32760: flush slice:
+ *        reset; STAT := <bytes_this_slice> ---> r_remain -= bytes; program
+ *                          <------------------- STAT=0  (ready for next slice)
+ *   ... repeat until the whole payload is sent ...
+ *                          <------------------- STAT=0  image verified
+ *                                               (STAT=1: image rejected)
+ *   STAT := END(0x3cc3)  ---------------------> finalise and boot
+ *
+ * The r_remain == 0 rule (critical):
+ *   Every host STAT write in the payload phase is a byte count; the loader
+ *   does r_remain -= count and stays in the receive loop while r_remain != 0.
+ *   It leaves the loop ONLY when r_remain hits EXACTLY 0, and a count larger
+ *   than r_remain underflows the 32-bit counter and wedges the loader until a
+ *   power cycle. Having left it, the loader verifies the image, publishes the
+ *   verdict in STAT (0 good, 1 rejected) and waits 2 s for END before
+ *   finalising regardless -- clearing its rescue-enable bit so boot_go boots
+ *   the new image -- so END only saves that wait. Hence:
+ *     - never send a slice/chunk count larger than what is outstanding;
+ *     - a STAT write is a command only once the loader has left the loop;
+ *     - the loader leaves the count in STAT while it programs the chunk, so
+ *       a lingering count does not distinguish "busy" from "verdict".
+ */
+
+#include <linux/crc32.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/iopoll.h>
+#include <linux/netdevice.h>
+#include <linux/overflow.h>
+#include <linux/rtnetlink.h>
+#include <linux/sched.h>
+#include <linux/workqueue.h>
+#include <net/dsa.h>
+#include <net/switchdev.h>
+
+#include "mxl862xx.h"
+#include "mxl862xx-api.h"
+#include "mxl862xx-cmd.h"
+#include "mxl862xx-fw.h"
+#include "mxl862xx-host.h"
+
+/* SB PDI registers (clause-22 SMDIO address space) */
+#define MXL862XX_SB_PDI_CTRL		0xe100
+#define MXL862XX_SB_PDI_ADDR		0xe101
+#define MXL862XX_SB_PDI_DATA		0xe102
+#define MXL862XX_SB_PDI_STAT		0xe103
+
+/* SB PDI CTRL modes */
+#define MXL862XX_SB_PDI_CTRL_RST	0x00
+#define MXL862XX_SB_PDI_CTRL_WR		0x02
+
+/* SB PDI handshake magic (published/consumed via STAT) */
+#define MXL862XX_SB_PDI_READY		0xc55c	/* loader idle, console loop */
+#define MXL862XX_SB_PDI_START		0xf48f
+#define MXL862XX_SB_PDI_END		0x3cc3
+
+/* Image verification verdict published in STAT once the receive loop ends */
+#define MXL862XX_SB_PDI_VERIFY_OK	0
+#define MXL862XX_SB_PDI_VERIFY_BAD	1
+
+/* Firmware transfer geometry */
+#define MXL862XX_FW_HDR_SIZE		20
+#define MXL862XX_FW_BANK_HALF		16384	/* words per half-bank */
+#define MXL862XX_FW_BANK_SLICE		32760	/* words per full slice */
+#define MXL862XX_FW_SB1_ADDR		0x7800	/* SB1 word address */
+
+/* Timeouts (generous upper bounds) */
+#define MXL862XX_FW_READY_TIMEOUT_MS	3000
+#define MXL862XX_FW_ACK_TIMEOUT_MS	5000
+#define MXL862XX_FW_ERASE_TIMEOUT_MS	300000
+#define MXL862XX_FW_WRITE_TIMEOUT_MS	60000
+#define MXL862XX_FW_REBOOT_DELAY_MS	5000
+#define MXL862XX_FW_REPROBE_DELAY_MS	500
+
+static int mxl862xx_sb_pdi_reset(struct mxl862xx_priv *priv)
+{
+	int ret;
+
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+				   MXL862XX_SB_PDI_CTRL_RST);
+	if (ret < 0)
+		return ret;
+
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_ADDR,
+				   MXL862XX_SB_PDI_CTRL_RST);
+	if (ret < 0)
+		return ret;
+
+	return mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA,
+				    MXL862XX_SB_PDI_CTRL_RST);
+}
+
+static int mxl862xx_sb_pdi_poll_stat(struct mxl862xx_priv *priv, u16 expected,
+				     unsigned long timeout_ms)
+{
+	int ret, val;
+
+	ret = read_poll_timeout(mxl862xx_smdio_read, val,
+				val < 0 || (u16)val == expected,
+				10000, timeout_ms * 1000, false,
+				priv, MXL862XX_SB_PDI_STAT);
+	if (val < 0)
+		return val;
+	return ret;
+}
+
+static int mxl862xx_sb_pdi_flush_slice(struct mxl862xx_priv *priv,
+				       u32 data_written)
+{
+	int ret;
+
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		return ret;
+
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT, data_written);
+	if (ret < 0)
+		return ret;
+
+	return mxl862xx_sb_pdi_poll_stat(priv, 0,
+					 MXL862XX_FW_WRITE_TIMEOUT_MS);
+}
+
+/* Flush the last slice, which ends the receive loop: the loader verifies the
+ * image and replaces the count in STAT with its verdict, so wait for the count
+ * to go rather than for a fixed value.
+ */
+static int mxl862xx_sb_pdi_flush_last(struct mxl862xx_priv *priv,
+				      u32 data_written)
+{
+	int ret, val;
+
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		return ret;
+
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT, data_written);
+	if (ret < 0)
+		return ret;
+
+	ret = read_poll_timeout(mxl862xx_smdio_read, val,
+				val < 0 || (u16)val != (u16)data_written,
+				10000, MXL862XX_FW_WRITE_TIMEOUT_MS * 1000,
+				false, priv, MXL862XX_SB_PDI_STAT);
+	if (val < 0)
+		return val;
+
+	if (!ret && (u16)val == MXL862XX_SB_PDI_VERIFY_OK)
+		return 0;
+
+	/* A final count of 1 is indistinguishable from the reject verdict, so
+	 * a timeout still holding it lands here too.
+	 */
+	if ((u16)val == MXL862XX_SB_PDI_VERIFY_BAD) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: loader rejected the image\n");
+		return -EBADMSG;
+	}
+
+	return ret ? ret : -EPROTO;
+}
+
+static void mxl862xx_flash_notify(struct devlink *dl, const char *status,
+				  u32 done, u32 total)
+{
+	devlink_flash_update_status_notify(dl, status, NULL, done, total);
+}
+
+/* MCUboot firmware image header */
+struct mxl862xx_fw_hdr {
+	__le32 image_type;
+	__le32 image_size_1;
+	__le32 image_checksum_1;
+	__le32 image_size_2;
+	__le32 image_checksum_2;
+} __packed;
+
+static int mxl862xx_flash_validate(struct mxl862xx_priv *priv,
+				   const struct firmware *fw,
+				   u32 *payload_size)
+{
+	const struct mxl862xx_fw_hdr *hdr;
+	u32 size1, size2, total;
+	const u8 *payload;
+	u32 crc;
+
+	if (fw->size < MXL862XX_FW_HDR_SIZE)
+		return -EINVAL;
+
+	hdr = (const struct mxl862xx_fw_hdr *)fw->data;
+	payload = fw->data + MXL862XX_FW_HDR_SIZE;
+	size1 = le32_to_cpu(hdr->image_size_1);
+	size2 = le32_to_cpu(hdr->image_size_2);
+
+	if (check_add_overflow(size1, size2, &total) ||
+	    total > fw->size - MXL862XX_FW_HDR_SIZE) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: firmware file too small for declared size\n");
+		return -EINVAL;
+	}
+
+	if (!total) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: firmware file with empty payload\n");
+		return -EINVAL;
+	}
+
+	if (size1) {
+		crc = ~crc32_le(~0U, payload, size1);
+		if (crc != le32_to_cpu(hdr->image_checksum_1)) {
+			dev_err(&priv->mdiodev->dev,
+				"flash: image 1 CRC mismatch (got %08x, expected %08x)\n",
+				crc, le32_to_cpu(hdr->image_checksum_1));
+			return -EINVAL;
+		}
+	}
+
+	if (size2) {
+		crc = ~crc32_le(~0U, payload + size1, size2);
+		if (crc != le32_to_cpu(hdr->image_checksum_2)) {
+			dev_err(&priv->mdiodev->dev,
+				"flash: image 2 CRC mismatch (got %08x, expected %08x)\n",
+				crc, le32_to_cpu(hdr->image_checksum_2));
+			return -EINVAL;
+		}
+	}
+
+	*payload_size = total;
+
+	return 0;
+}
+
+static int mxl862xx_flash_firmware(struct mxl862xx_priv *priv,
+				   const struct firmware *fw,
+				   u32 payload_size, struct devlink *dl)
+{
+	const u8 *payload = fw->data + MXL862XX_FW_HDR_SIZE;
+	u32 word_idx = 0, data_written = 0, idx = 0;
+	unsigned long next_notify = jiffies - 1;
+	u16 word, fdata;
+	int ret, i;
+
+	/* Step 1: reboot the firmware into MCUboot rescue mode */
+	ret = mxl862xx_api_wrap(priv, SYS_MISC_FW_UPDATE, NULL, 0,
+				false, false);
+	if (ret) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: FW_UPDATE command failed: %pe\n",
+			ERR_PTR(ret));
+		return ret;
+	}
+
+	/* Step 2: wait for bootloader ready */
+	mxl862xx_flash_notify(dl, "Waiting for bootloader", 0, 0);
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		goto write_err;
+
+	/* Failures from here on end up at no_end, which returns the error
+	 * without signalling END -- see there.
+	 */
+	ret = mxl862xx_sb_pdi_poll_stat(priv, MXL862XX_SB_PDI_READY,
+					MXL862XX_FW_READY_TIMEOUT_MS);
+	if (ret) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: bootloader not ready: %pe\n", ERR_PTR(ret));
+		goto no_end;
+	}
+
+	/* Step 3: start handshake */
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT,
+				   MXL862XX_SB_PDI_START);
+	if (ret < 0)
+		goto write_err;
+
+	ret = mxl862xx_sb_pdi_poll_stat(priv, MXL862XX_SB_PDI_START + 1,
+					MXL862XX_FW_ACK_TIMEOUT_MS);
+	if (ret) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: start handshake failed: %pe\n", ERR_PTR(ret));
+		goto no_end;
+	}
+
+	/* Step 4: transfer image header */
+	mxl862xx_flash_notify(dl, "Erasing flash", 0, 0);
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+				   MXL862XX_SB_PDI_CTRL_WR);
+	if (ret < 0)
+		goto write_err;
+
+	for (i = 0; i < MXL862XX_FW_HDR_SIZE / 2; i++) {
+		word = fw->data[i * 2] |
+		       ((u16)fw->data[i * 2 + 1] << 8);
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA, word);
+		if (ret < 0)
+			goto write_err;
+	}
+
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		goto write_err;
+
+	/* the byte count in STAT triggers the erase */
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT,
+				   MXL862XX_FW_HDR_SIZE);
+	if (ret < 0)
+		goto write_err;
+
+	/* ACK is byte count + 1 */
+	ret = mxl862xx_sb_pdi_poll_stat(priv, MXL862XX_FW_HDR_SIZE + 1,
+					MXL862XX_FW_ACK_TIMEOUT_MS);
+	if (ret) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: header ACK failed: %pe\n", ERR_PTR(ret));
+		goto no_end;
+	}
+
+	/* Step 5: wait for erase to complete */
+	ret = mxl862xx_sb_pdi_poll_stat(priv, 0,
+					MXL862XX_FW_ERASE_TIMEOUT_MS);
+	if (ret) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: erase timeout: %pe\n", ERR_PTR(ret));
+		goto no_end;
+	}
+
+	/* Step 6: transfer payload */
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+				   MXL862XX_SB_PDI_CTRL_WR);
+	if (ret < 0)
+		goto write_err;
+
+	while (idx < payload_size) {
+		cond_resched();
+		if (idx + 1 < payload_size) {
+			fdata = payload[idx] |
+				((u16)payload[idx + 1] << 8);
+			idx += 2;
+			data_written += 2;
+		} else {
+			fdata = payload[idx];
+			idx++;
+			data_written++;
+		}
+
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA, fdata);
+		if (ret < 0)
+			goto write_err;
+		word_idx++;
+
+		if (idx >= payload_size) {
+			ret = mxl862xx_sb_pdi_flush_last(priv, data_written);
+			break;
+		}
+
+		/* Half-bank boundary: switch to SB1 address */
+		if (word_idx == MXL862XX_FW_BANK_HALF) {
+			ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+						   MXL862XX_SB_PDI_CTRL_RST);
+			if (ret < 0)
+				goto write_err;
+
+			ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_ADDR,
+						   MXL862XX_FW_SB1_ADDR);
+			if (ret < 0)
+				goto write_err;
+
+			ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+						   MXL862XX_SB_PDI_CTRL_WR);
+			if (ret < 0)
+				goto write_err;
+		} else if (word_idx >= MXL862XX_FW_BANK_SLICE) {
+			ret = mxl862xx_sb_pdi_flush_slice(priv, data_written);
+			if (ret) {
+				dev_err(&priv->mdiodev->dev,
+					"flash: write timeout at %u/%u: %pe\n",
+					idx, payload_size, ERR_PTR(ret));
+				goto no_end;
+			}
+			word_idx = 0;
+			data_written = 0;
+			ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+						   MXL862XX_SB_PDI_CTRL_WR);
+			if (ret < 0)
+				goto write_err;
+
+			if (time_after(jiffies, next_notify)) {
+				mxl862xx_flash_notify(dl, "Flashing", idx,
+						      payload_size);
+				next_notify = jiffies + msecs_to_jiffies(500);
+			}
+		}
+	}
+
+	if (ret) {
+		dev_err(&priv->mdiodev->dev,
+			"flash: final slice failed: %pe\n", ERR_PTR(ret));
+		goto no_end;
+	}
+
+	mxl862xx_flash_notify(dl, "Flashing", payload_size, payload_size);
+
+	/* Success: the loader has left the receive loop at r_remain == 0 and
+	 * verified the image, so END(0x3cc3) is a finalise/boot request rather
+	 * than a byte count. Signal it here -- and only here -- to boot the new
+	 * image without waiting out the loader's 2 s END timeout.
+	 */
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT,
+				   MXL862XX_SB_PDI_END);
+	if (ret < 0)
+		dev_warn(&priv->mdiodev->dev,
+			 "flash: END signalling failed, waiting the loader out: %pe\n",
+			 ERR_PTR(ret));
+
+	msleep(MXL862XX_FW_REBOOT_DELAY_MS);
+	return 0;
+
+write_err:
+	dev_err(&priv->mdiodev->dev, "flash: SMDIO write failed: %pe\n",
+		ERR_PTR(ret));
+no_end:
+	/* A failure leaves the loader mid transfer; do not signal END (a STAT
+	 * write is a byte count then, and END would be misread as one, risking
+	 * a receive-counter underflow). Return the error; the caller reprobes.
+	 */
+	return ret;
+}
+
+int mxl862xx_devlink_info_get(struct dsa_switch *ds,
+			      struct devlink_info_req *req,
+			      struct netlink_ext_ack *extack)
+{
+	struct mxl862xx_priv *priv = ds->priv;
+	char buf[16];
+	int ret;
+
+	/* A 0 part number means the CHIP ID read failed or the part is
+	 * unfused; omit it rather than publish a bogus "0000" that fwupd
+	 * would match firmware against -- it then falls back to the driver
+	 * name.
+	 */
+	if (priv->asic_id) {
+		snprintf(buf, sizeof(buf), "%04X", priv->asic_id);
+		ret = devlink_info_version_fixed_put(req,
+						     DEVLINK_INFO_VERSION_GENERIC_ASIC_ID,
+						     buf);
+		if (ret)
+			return ret;
+
+		snprintf(buf, sizeof(buf), "%u", priv->asic_rev);
+		ret = devlink_info_version_fixed_put(req,
+						     DEVLINK_INFO_VERSION_GENERIC_ASIC_REV,
+						     buf);
+		if (ret)
+			return ret;
+	}
+
+	/* An all-zero version is the cache a failed flash left behind, not a
+	 * released firmware; omit it like the part number above.
+	 */
+	if (!priv->fw_version.major && !priv->fw_version.minor &&
+	    !priv->fw_version.revision)
+		return 0;
+
+	snprintf(buf, sizeof(buf), "%u.%u.%u",
+		 priv->fw_version.major, priv->fw_version.minor,
+		 priv->fw_version.revision);
+
+	ret = devlink_info_version_running_put(req,
+			DEVLINK_INFO_VERSION_GENERIC_FW, buf);
+	if (ret)
+		return ret;
+
+	/* boots this image from its own flash: stored == running */
+	return devlink_info_version_stored_put(req,
+			DEVLINK_INFO_VERSION_GENERIC_FW, buf);
+}
+
+int mxl862xx_devlink_flash_update(struct dsa_switch *ds,
+				  struct devlink_flash_update_params *params,
+				  struct netlink_ext_ack *extack)
+{
+	struct mxl862xx_priv *priv = ds->priv;
+	struct dsa_port *dp;
+	u32 payload_size;
+	int ret, err, i;
+
+	if (params->component) {
+		NL_SET_ERR_MSG_MOD(extack, "component is not supported");
+		return -EOPNOTSUPP;
+	}
+
+	/* Written under the instance lock this call is holding. */
+	if (priv->shutting_down) {
+		NL_SET_ERR_MSG_MOD(extack, "device is shutting down");
+		return -ENODEV;
+	}
+
+	/* A previous flash is still waiting for its reprobe: the firmware API
+	 * is short-circuited, so the raw SB PDI writes below would run against
+	 * a switch this driver no longer tracks.
+	 */
+	if (priv->skip_teardown) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "a previous flash awaits its reprobe");
+		return -EBUSY;
+	}
+
+	ret = mxl862xx_flash_validate(priv, params->fw, &payload_size);
+	if (ret) {
+		NL_SET_ERR_MSG_MOD(extack, "firmware image validation failed");
+		return ret;
+	}
+
+	dev_info(ds->dev, "flash: running firmware %u.%u.%u\n",
+		 priv->fw_version.major, priv->fw_version.minor,
+		 priv->fw_version.revision);
+
+	/* Close ports while the firmware is still alive so the DSA core's
+	 * MDB/FDB tracking is drained, and detach user ports so userspace
+	 * cannot reopen them during the flash. The conduit is only closed,
+	 * not detached: it belongs to the MAC driver. This driver binds a
+	 * single switch with a direct host link and no cascade ports, so the
+	 * conduit serves only this switch, and flashing it reboots the switch,
+	 * which takes the tree down regardless.
+	 */
+	rtnl_lock();
+	dsa_switch_for_each_user_port(dp, ds) {
+		if (dp->user) {
+			dev_close(dp->user);
+			netif_device_detach(dp->user);
+		}
+	}
+	dsa_switch_for_each_cpu_port(dp, ds)
+		dev_close(dp->conduit);
+	/* The bridge defers the STP state changes triggered by closing
+	 * the ports; let them reach the firmware while it is still alive.
+	 */
+	switchdev_deferred_process();
+	rtnl_unlock();
+
+	mutex_lock_nested(&priv->mdiodev->bus->mdio_lock, MDIO_MUTEX_NESTED);
+	priv->block_host = true;
+	mutex_unlock(&priv->mdiodev->bus->mdio_lock);
+
+	set_bit(MXL862XX_FLAG_WORK_STOPPED, &priv->flags);
+	disable_delayed_work_sync(&priv->stats_work);
+	cancel_work_sync(&priv->crc_err_work);
+	for (i = 0; i < ds->num_ports; i++)
+		cancel_work_sync(&priv->ports[i].host_flood_work);
+
+	ret = mxl862xx_flash_firmware(priv, params->fw, payload_size,
+				      ds->devlink);
+	if (ret)
+		NL_SET_ERR_MSG_MOD(extack, "firmware transfer failed");
+
+	if (!ret) {
+		mutex_lock_nested(&priv->mdiodev->bus->mdio_lock,
+				  MDIO_MUTEX_NESTED);
+		/* Keep block_host set so host writes stay blocked, but let the
+		 * readiness poll below read the freshly booted firmware.
+		 */
+		priv->flash_owner = current;
+		mutex_unlock(&priv->mdiodev->bus->mdio_lock);
+
+		/* Refresh the cached versions so the flash update only
+		 * completes once the new firmware is confirmed running and
+		 * devlink dev info reports it. Must happen before setting
+		 * skip_teardown, which discards all firmware API reads.
+		 */
+		ret = mxl862xx_wait_ready(ds);
+		if (ret)
+			NL_SET_ERR_MSG_MOD(extack,
+					   "new firmware did not become ready");
+	}
+
+	if (ret) {
+		/* The switch is in MCUboot with erased or partly written flash;
+		 * drop the cached identity so devlink dev info stops reporting
+		 * the pre-flash version until the reprobe re-reads the truth.
+		 */
+		memset(&priv->fw_version, 0, sizeof(priv->fw_version));
+		priv->asic_id = 0;
+		priv->asic_rev = 0;
+	}
+
+	mutex_lock_nested(&priv->mdiodev->bus->mdio_lock, MDIO_MUTEX_NESTED);
+	priv->flash_owner = NULL;
+	priv->block_host = false;
+	priv->skip_teardown = true;
+	mutex_unlock(&priv->mdiodev->bus->mdio_lock);
+
+	/* Reinitialise through a deferred re-probe: remove() runs with
+	 * skip_teardown set, then a fresh probe() starts against whatever
+	 * the switch now runs. The core skips the re-probe if the device
+	 * is unbound or shut down before it fires.
+	 */
+	err = device_schedule_reprobe(ds->dev, MXL862XX_FW_REPROBE_DELAY_MS);
+
+	return ret ? ret : err;
+}
+
+/* The devlink core holds the instance lock across a flash, so taking it here
+ * waits for a transfer in flight instead of cutting the image in half, and
+ * bars one that has not started yet.
+ */
+void mxl862xx_flash_shutdown(struct dsa_switch *ds)
+{
+	struct mxl862xx_priv *priv = ds->priv;
+
+	if (!ds->devlink)
+		return;
+
+	devl_lock(ds->devlink);
+	priv->shutting_down = true;
+	devl_unlock(ds->devlink);
+}
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-fw.h b/drivers/net/dsa/mxl862xx/mxl862xx-fw.h
new file mode 100644
index 000000000000..15ed3a46bcfe
--- /dev/null
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-fw.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef __MXL862XX_FW_H
+#define __MXL862XX_FW_H
+
+#include <net/dsa.h>
+
+struct mxl862xx_priv;
+
+int mxl862xx_devlink_info_get(struct dsa_switch *ds,
+			      struct devlink_info_req *req,
+			      struct netlink_ext_ack *extack);
+int mxl862xx_devlink_flash_update(struct dsa_switch *ds,
+				  struct devlink_flash_update_params *params,
+				  struct netlink_ext_ack *extack);
+void mxl862xx_flash_shutdown(struct dsa_switch *ds);
+
+#endif /* __MXL862XX_FW_H */
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-host.c b/drivers/net/dsa/mxl862xx/mxl862xx-host.c
index 11759fa6069b..4b3956a518cf 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-host.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-host.c
@@ -12,9 +12,11 @@
 #include <linux/crc16.h>
 #include <linux/iopoll.h>
 #include <linux/limits.h>
+#include <linux/sched.h>
 #include <linux/unaligned.h>
 #include <net/dsa.h>
 #include "mxl862xx.h"
+#include "mxl862xx-cmd.h"
 #include "mxl862xx-host.h"
 
 #define CTRL_BUSY_MASK			BIT(15)
@@ -340,6 +342,24 @@ int mxl862xx_api_wrap(struct mxl862xx_priv *priv, u16 cmd, void *_data,
 
 	mutex_lock_nested(&priv->mdiodev->bus->mdio_lock, MDIO_MUTEX_NESTED);
 
+	if (priv->skip_teardown) {
+		ret = read ? -ENODEV : 0;
+		goto out;
+	}
+
+	/* During the post-flash readiness poll block_host stays set, but the
+	 * flash path's own firmware version reads must reach the new image;
+	 * host writes stay blocked so stale resource IDs cannot corrupt it.
+	 * A blocked write reports success: the reprobe discards the switch
+	 * configuration anyway, and a bridge tearing down over a flash must
+	 * not see port_vlan_del() fail, which leaks its VLAN group.
+	 */
+	if (priv->block_host && cmd != SYS_MISC_FW_UPDATE &&
+	    !(read && priv->flash_owner == current)) {
+		ret = read ? -EBUSY : 0;
+		goto out;
+	}
+
 	max = (size + 1) / 2;
 
 	ret = mxl862xx_busy_wait(priv);
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx.c b/drivers/net/dsa/mxl862xx/mxl862xx.c
index cfa7e3e269a2..5668aac9ef7a 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx.c
@@ -21,6 +21,7 @@
 #include "mxl862xx.h"
 #include "mxl862xx-api.h"
 #include "mxl862xx-cmd.h"
+#include "mxl862xx-fw.h"
 #include "mxl862xx-host.h"
 #include "mxl862xx-phylink.h"
 
@@ -71,6 +72,13 @@ static const struct ethtool_rmon_hist_range mxl862xx_rmon_ranges[] = {
 #define MXL862XX_READY_TIMEOUT_MS	10000
 #define MXL862XX_READY_POLL_MS		100
 
+/* Chip ID registers, read via SYS_MISC_REG_RD */
+#define MXL862XX_CHIPID_L		0xc0d28884
+#define MXL862XX_CHIPID_M		0xc0d28888
+#define MXL862XX_CHIPID_L_PNUML		GENMASK(15, 12)
+#define MXL862XX_CHIPID_M_PNUMM		GENMASK(11, 0)
+#define MXL862XX_CHIPID_M_VERSION	GENMASK(14, 12)
+
 #define MXL862XX_TCM_INST_SEL		0xe00
 #define MXL862XX_TCM_CBS		0xe12
 #define MXL862XX_TCM_EBS		0xe13
@@ -222,7 +230,45 @@ static int mxl862xx_phy_write_c45_mii_bus(struct mii_bus *bus, int addr,
 	return mxl862xx_phy_write_mmd(bus->priv, addr, devadd, regnum, val);
 }
 
-static int mxl862xx_wait_ready(struct dsa_switch *ds)
+/* The CHIP ID registers are only readable through the firmware mailbox, so
+ * the values are cached here and stay zero while no firmware answers.
+ */
+static int mxl862xx_read_chip_id(struct mxl862xx_priv *priv)
+{
+	struct mxl862xx_sys_reg_rw reg = {};
+	u16 chipid_l, chipid_m;
+	int ret;
+
+	reg.addr = cpu_to_le32(MXL862XX_CHIPID_L);
+	ret = MXL862XX_API_READ(priv, SYS_MISC_REG_RD, reg);
+	if (ret)
+		return ret;
+	chipid_l = le32_to_cpu(reg.val);
+
+	reg.addr = cpu_to_le32(MXL862XX_CHIPID_M);
+	ret = MXL862XX_API_READ(priv, SYS_MISC_REG_RD, reg);
+	if (ret)
+		return ret;
+	chipid_m = le32_to_cpu(reg.val);
+
+	priv->asic_id = FIELD_GET(MXL862XX_CHIPID_L_PNUML, chipid_l) |
+			FIELD_GET(MXL862XX_CHIPID_M_PNUMM, chipid_m) << 4;
+	priv->asic_rev = FIELD_GET(MXL862XX_CHIPID_M_VERSION, chipid_m);
+
+	return 0;
+}
+
+/**
+ * mxl862xx_wait_ready - wait for the switch firmware to become operational
+ * @ds: DSA switch instance
+ *
+ * Poll the firmware until it reports its version and accepts
+ * configuration commands, then cache the firmware version and chip ID.
+ * Takes at least two seconds.
+ *
+ * Return: 0 on success or a negative error code.
+ */
+int mxl862xx_wait_ready(struct dsa_switch *ds)
 {
 	struct mxl862xx_sys_fw_image_version ver = {};
 	unsigned long start = jiffies, timeout;
@@ -254,6 +300,11 @@ static int mxl862xx_wait_ready(struct dsa_switch *ds)
 		priv->fw_version.major = ver.iv_major;
 		priv->fw_version.minor = ver.iv_minor;
 		priv->fw_version.revision = le16_to_cpu(ver.iv_revision);
+
+		ret = mxl862xx_read_chip_id(priv);
+		if (ret)
+			dev_warn(ds->dev, "failed to read chip ID: %pe\n",
+				 ERR_PTR(ret));
 		return 0;
 
 not_ready_yet:
@@ -1572,6 +1623,12 @@ static int mxl862xx_port_mdb_del(struct dsa_switch *ds, int port,
 	ether_addr_copy(qparam.mac, mdb->addr);
 
 	ret = MXL862XX_API_READ(priv, MXL862XX_MAC_TABLEENTRYQUERY, qparam);
+	/* Post-flash teardown: the firmware and its MAC table are gone, so
+	 * there is nothing left to delete. Outside it, -ENODEV is a bus error
+	 * and must be reported.
+	 */
+	if (ret == -ENODEV && priv->skip_teardown)
+		return 0;
 	if (ret)
 		return ret;
 
@@ -2086,6 +2143,8 @@ static const struct dsa_switch_ops mxl862xx_switch_ops = {
 	.get_pause_stats = mxl862xx_get_pause_stats,
 	.get_rmon_stats = mxl862xx_get_rmon_stats,
 	.get_stats64 = mxl862xx_get_stats64,
+	.devlink_info_get = mxl862xx_devlink_info_get,
+	.devlink_flash_update = mxl862xx_devlink_flash_update,
 };
 
 static int mxl862xx_probe(struct mdio_device *mdiodev)
@@ -2178,6 +2237,8 @@ static void mxl862xx_shutdown(struct mdio_device *mdiodev)
 
 	priv = ds->priv;
 
+	mxl862xx_flash_shutdown(ds);
+
 	dsa_switch_shutdown(ds);
 
 	set_bit(MXL862XX_FLAG_WORK_STOPPED, &priv->flags);
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx.h b/drivers/net/dsa/mxl862xx/mxl862xx.h
index 432a5f3f2e08..2d38885ecfda 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx.h
+++ b/drivers/net/dsa/mxl862xx/mxl862xx.h
@@ -303,6 +303,10 @@ struct mxl862xx_fw_version {
  *                      flooding)
  * @fw_version:         cached firmware version, populated at probe and
  *                      compared with MXL862XX_FW_VER_MIN()
+ * @asic_id:            chip part number read from the CHIP ID registers,
+ *                      reported as the devlink "asic.id" fixed version
+ * @asic_rev:           chip version read from the CHIP ID registers,
+ *                      reported as the devlink "asic.rev" fixed version
  * @serdes_ports:       SerDes interfaces incl. sub-interfaces in case of
  *                      10G_QXGMII or QSGMII
  * @serdes_refcount:    per-XPCS count of sub-ports enabled by phylink;
@@ -319,6 +323,15 @@ struct mxl862xx_fw_version {
  * @evlan_ingress_size: per-port ingress Extended VLAN block size
  * @evlan_egress_size:  per-port egress Extended VLAN block size
  * @vf_block_size:      per-port VLAN Filter block size
+ * @block_host:         reject firmware API commands (except FW_UPDATE)
+ *                      during a firmware flash
+ * @flash_owner:        task running the post-flash readiness poll; only its
+ *                      own firmware reads pass block_host
+ * @skip_teardown:      discard firmware API commands during the teardown
+ *                      triggered by the post-flash reprobe
+ * @shutting_down:      set under the devlink instance lock once ->shutdown()
+ *                      has begun, so no flash starts while the system is
+ *                      going down
  * @stats_work:         periodic work item that polls RMON hardware counters
  *                      and accumulates them into 64-bit per-port stats
  */
@@ -329,6 +342,8 @@ struct mxl862xx_priv {
 	unsigned long flags;
 	u16 drop_meter;
 	struct mxl862xx_fw_version fw_version;
+	u16 asic_id;
+	u8 asic_rev;
 	struct mxl862xx_pcs serdes_ports[8];
 	int serdes_refcount[2];
 	struct mutex serdes_lock;
@@ -337,7 +352,13 @@ struct mxl862xx_priv {
 	u16 evlan_ingress_size;
 	u16 evlan_egress_size;
 	u16 vf_block_size;
+	struct task_struct *flash_owner;
+	bool block_host;
+	bool skip_teardown;
+	bool shutting_down;
 	struct delayed_work stats_work;
 };
 
+int mxl862xx_wait_ready(struct dsa_switch *ds);
+
 #endif /* __MXL862XX_H */
-- 
2.55.0

[PATCH net-next v16 5/6] net: dsa: mxl862xx: recover switch stuck in MCUboot rescue mode

[Daniel Golle]

A broken or interrupted firmware image, or the sticky rescue bit, keeps
the switch in its MCUboot bootloader, which exposes only the clause-22
SMDIO download interface. The clause-45 MMD API never comes up, so probe
would fail with -ETIMEDOUT and the only way back would be the switch's
UART console, or a power cycle or out-of-band reset (not currently
implemented).

Probe for the loader over SB PDI at setup, before any clause-45 access,
since nothing answers the firmware mailbox in MCUboot: every command
there runs into its own timeout, and probe gives up ten seconds later.
A scratch write to two mailbox registers first establishes
that a switch is there at all. It reaches a running firmware as well,
but lands in registers that firmware does not read, so it is inert
there. The status register the loader publishes then tells the cases
apart without touching C45: a running firmware, which answers with its
own non-zero status word (0x0003 on the firmware tested), so probe
continues normally; a loader idle in its console loop, confirmed live
by a register-read challenge; a loader wedged mid-download, which
publishes zero, or the count of the chunk it is programming or erasing
for once a failed clause-45 wait has ruled a firmware out; a loader
left in the opening handshake, waiting for an image header no later
session can supply; the flashless download loop, which this driver
cannot drive; and a switch whose scratch write does not latch --
absent, unpowered, misdescribed in the device tree (wrong address or
bus, or a reset GPIO with inverted polarity), or with its SB PDI window
somewhere other than the OTP reset offsets assumed here. The first four
enter rescue mode or normal operation, the last two fail probe at once
with -EOPNOTSUPP and -ENODEV, ahead of that timeout.

A loader that publishes the ready magic but never services the
register-read challenge fails probe too, with -ENXIO. The challenge is
what tells the loader apart from a firmware whose status word happens
to read the same value, and offering to flash a healthy firmware would
be worse than refusing to bind, so a mailbox that does not answer is
treated as unusable rather than as a flash target. Every loader tested
services it.

In rescue mode the switch registers without user interfaces so devlink
stays available: user ports fail port_setup with -ENODEV (the DSA core
re-registers them as unused) while shared and CPU ports succeed, and the
CPU port works on its fixed link with mac_select_pcs returning no PCS.
Firmware API commands fail fast with -ENODEV and the port and STP
callbacks become no-ops.

An interrupted download can leave the loader wedged mid-payload. A
background work item off the devlink flash path waits out an erase the
dead session left running, then drains the loader back to a clean ready
state by feeding the outstanding byte count one byte at a time, which
takes tens of minutes for a large image and is logged as it progresses;
until then devlink dev info reports no version and devlink dev flash
returns -EBUSY, and -EIO once a drain has failed for good.
Reaching the end of the count is all the drain does: the loader then
verifies the corrupt image and returns to its console loop on its own,
so the drain reprobes and lets the probe-time detection re-classify the
switch -- a valid image that a last-moment interruption left bootable
comes up as running firmware, with no second-guessing in the drain path.

The re-probe the drain schedules is the same device_schedule_reprobe()
hand-off the flash path uses: the core skips it if the device is
unbound or shut down before it fires, so a drain finishing after the
driver is gone does nothing. Should scheduling it fail, recovery is
marked failed, since the loader would otherwise sit at a clean ready
state that nothing reclassifies while devlink keeps promising that a
retry will work.

The CHIP ID registers need a running firmware, so no asic.id/asic.rev is
reported in rescue mode. Once the loader is ready, devlink dev info
reports the null firmware version "0.0.0" as both running and stored:

  $ devlink dev info mdio_bus/mdio-bus:10
  mdio_bus/mdio-bus:10:
    driver mxl862xx
    versions:
        running:
          fw 0.0.0
        stored:
          fw 0.0.0

An operational switch never reports 0.0.0 (a released firmware's major
is non-zero), so version-comparing tools like fwupd offer every release
as an upgrade, recovering the switch through the regular flash flow,
matched on the driver name. The flash skips the FW_UPDATE command since
MCUboot is already waiting. A successful flash reboots the switch into
the new firmware and the reprobe then brings the driver up against it
normally; after a failed one the switch is still in MCUboot, rescue mode
is detected again and the flash can be retried, unless the transfer
failed with the opening handshake already acknowledged, which leaves the
loader waiting for a header only a power cycle clears.

Assisted-by: LLM
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
v16:
 - drop the claim that the clause-45 API floods the log with CRC errors
   when no firmware answers, here and in the comments. The mailbox
   commands run into their timeouts instead, and testing the
   stuck-in-MCUboot paths produces no such message. What probing SB PDI
   first saves is the ten seconds of polling and the -ETIMEDOUT that
   ends probe
 - move the rescue-mode branch of mxl862xx_setup() into a function of
   its own, which brings its messages back inside 100 columns
 - state a fact in the -EBUSY extack of a running recovery, dropping
   the retry advice
 - trim the comment on mxl862xx_rescue_drain(), whose protocol detail
   is in the file header already, and order its declarations longest
   line first
 - treat a byte count that outlives the settle step as a busy loader
   rather than a running firmware, and wait out an erase from the dead
   session before draining, so a host that died during the loader's
   erase no longer fails probe with the -ETIMEDOUT this patch exists to
   avoid (found by Sashiko AI review)
 - poll the status register every 10 ms rather than every 50 us for the
   waits now measured in minutes
 - drop the loader's clean ready state along with the cached identity
   when a flash fails, so devlink dev info stops reporting 0.0.0, which
   means "ready to accept an image", for a loader left mid transfer
   (found by Sashiko AI review)
 - state facts in the extack for a failed recovery; the remedies, which
   differ per cause, are in the documentation (found by Sashiko AI
   review)
 - name -ECANCELED in the documented return sets that can produce it,
   and the opening handshake among the detection outcomes in the commit
   message (found by Sashiko AI review)

v15:
 - classify a status register left in the download handshake as a loader
   needing a power cycle, rather than as a running firmware, which made
   probe fail with the CRC-error storm this patch avoids (found by
   Sashiko AI review)
 - give the loader one step to publish its next state when detection
   runs after a failed clause-45 wait, so the count of a chunk it is
   still programming is not read as a firmware status word (found by
   Sashiko AI review)
 - abort the drain polls as soon as teardown asks for it, instead of
   holding up unbind and shutdown for up to 17 s (found by Sashiko AI
   review)
 - pair the rescue_mode accesses with WRITE_ONCE()/READ_ONCE(), like the
   sibling rescue flags (found by Sashiko AI review)

v14:
 - initialise the SerDes state once mxl862xx_wait_ready() has cached
   the firmware version, still before the rescue-mode early return,
   so PCS setup can depend on the running firmware

v13: no changes

v12: no changes

v11:
 - schedule the post-drain re-probe with device_schedule_reprobe() too,
   instead of a driver-owned work item
 - a drain whose re-probe hand-off fails still marks recovery failed, so
   devlink does not keep promising a retry

v10:
 - share the SB PDI timeouts with the flash path: one constant for the
   verify wait (15 s) and one for a single 1-byte mailbox step (2 s),
   the latter also replacing the separate detection timeout. The
   last-slice flush gets the sum of the write and verify budgets, since
   it cannot see the boundary between programming and verifying (found
   by Sashiko AI review)
 - report a reprobe hand-off that cannot be set up after a successful
   drain, instead of leaving devlink answering "retry shortly" for good
   for a loader sitting at a clean READY (found by Sashiko AI review)
 - drop heal_lock and mxl862xx_stop_work() with it: making the flag test
   and the queueing atomic was never the guarantee its comment claimed,
   and the reprobe now decides for itself whether it may still run
   (found by Sashiko AI review)
 - return -ENXIO rather than a propagated -ETIMEDOUT when the loader
   never re-arms READY for the register-read challenge, and correct the
   documented return sets of mxl862xx_rescue_mode_detect() and
   mxl862xx_rescue_drain_finish() (found by Sashiko AI review)
 - explain why STAT == 0 during a drain is unambiguous: by the
   r_remain == 0 rule the loader cannot be both inside the receive loop
   asking for a chunk and publishing a verdict (found by Sashiko AI
   review)
 - commit message: a running firmware is not "left untouched", the
   presence probe writes two mailbox scratch registers which are inert
   to it; an SB PDI window away from the OTP reset offsets also yields
   -ENODEV; and describe the -ENXIO outcome for a READY loader that
   never services the challenge (found by Sashiko AI review)

v9: no changes

v8:
 - never send END from the drain: the loader keeps the host's byte count
   in its status register while it programs a chunk, so a lingering count
   cannot be told from the "image rejected" verdict, and END written into
   the receive loop is consumed as a 15555-byte count and underflows the
   receive counter. Wait for the loader to ask for the next chunk or to
   return to its console loop instead, since it finalises on its own
   (found by Sashiko AI review)
 - initialise the SerDes state before the rescue-mode early return, so
   the window between a successful rescue-mode flash clearing
   rescue_mode and the reprobe cannot hand phylink a PCS with no ops and
   an uninitialised mutex (found by Sashiko AI review)
 - do not fail probe when the 1-byte slice-advance leaves the wedged
   loader somewhere other than asking for the next chunk: a download
   interrupted with exactly one byte outstanding completes on that byte,
   after which the loader verifies and returns to its console loop
   (found by Sashiko AI review)
 - report a failed drain and refuse further flashes with -EIO and an
   extack asking for a power cycle, instead of leaving devlink to answer
   "retry shortly" forever for a switch that never becomes ready (found
   by Sashiko AI review)
 - reset the mailbox before the presence probe: a download interrupted
   with the write latch armed made the scratch write land in switch
   memory instead, so detection returned -ENODEV for the very state it
   exists to recover (found by Sashiko AI review)
 - tell an SMDIO bus error apart from a loader failing the register-read
   challenge, and check the reset issued after it (found by Sashiko AI
   review)
 - reject DSA links before the rescue-mode shortcut, so an unsupported
   cascade topology fails probe in rescue mode too (found by Sashiko AI
   review)
 - serialise the self-heal's reprobe hand-off against teardown with a
   mutex (found by Sashiko AI review)
 - log the drain's progress, name its timeouts, and describe its real
   duration (found by Sashiko AI review)
 - WRITE_ONCE() the rescue_ready stores, document what orders
   rescue_mode, and correct the detection kernel-doc and the note on the
   OTP-configurable SB PDI register offsets (found by Sashiko AI review)

v7:
 - queue the reprobe as a delayed work item from the background
   self-heal, following the previous patch's move off the reprobe
   kthread
 - report the rescue-mode firmware version under
   DEVLINK_INFO_VERSION_GENERIC_FW too
 - drop two redundant rescue-recovery log lines; the setup message
   ("switch in MCUboot with an interrupted download, recovering in
   background") already says it
 - return distinct errno from rescue_mode_detect() so an absent switch
   (-ENODEV), one strapped into flashless-download mode (-EOPNOTSUPP)
   and one that answers SB PDI READY but fails the register-read
   challenge, or wedges without draining (-ENXIO), are no longer all
   reported as -ENODEV

v6:
 - after the background drain finalises the interrupted transfer,
   reprobe and let the probe-time detection re-classify the switch, so
   a valid image a last-moment interruption left bootable is picked up
   as running firmware; rescue_drain() no longer inspects or reports
   the outcome (its stale kernel-doc claiming a "return 1" case is gone)
 - poll the drain status register with read_poll_timeout() as well,
   which evaluates the condition once more after the deadline, matching
   the poll fix in the previous patch
 - treat the flashless-download loop (STAT 0xc33c) as an unsupported
   configuration and fail probe with -ENODEV, rather than advertising it
   as flashable when the console flash path cannot drive it

v5:
 - detect the switch state from the value MCUboot publishes in the SB
   PDI STAT register (loader ready, wedged download, or running
   firmware), confirming a live console loader with a register-read
   challenge, instead of trusting a bare SMDIO scratch write
 - fail probe with -ENODEV over SB PDI when the switch does not respond
   at all -- absent, unpowered, or misdescribed in the device tree --
   instead of letting the clause-45 API flood the log with CRC errors
 - drain a wedged interrupted download back to a clean ready state from
   a background work item so the multi-minute recovery never holds the
   devlink instance lock, and refuse devlink dev info and flash until it
   is ready
 - report the null firmware version as the stored version too, matching
   the running/stored reporting of the previous patch
 - do not report asic.id/asic.rev in rescue mode as the CHIP ID
   registers are unreadable without firmware; recovery tools match on
   the driver name and the "0.0.0" version instead (follows the numeric
   asic.id change in the previous patch)
 - move the devlink documentation into its own patch

v4:
 - log a distinct diagnostic when rescue mode detection fails on an
   SMDIO bus error instead of silently treating it as "not in
   rescue mode"
 - clear the rescue_mode flag under the MDIO bus lock, following
   the flag write locking in the previous patch

v3:
 - report the canonical null version "0.0.0" instead of
   "mcuboot-rescue" so that version-comparing update tools like
   fwupd offer any available release as an upgrade for recovery
 - check the rescue_mode flag under the MDIO bus lock, following
   the block_host/skip_teardown change in the previous patch

v2: new patch, allowing recovery from a failed or interrupted update
    without having to use a special recovery OS image (Andrew Lunn)

 drivers/net/dsa/mxl862xx/mxl862xx-fw.c      | 491 +++++++++++++++++++-
 drivers/net/dsa/mxl862xx/mxl862xx-fw.h      |   3 +
 drivers/net/dsa/mxl862xx/mxl862xx-host.c    |   8 +
 drivers/net/dsa/mxl862xx/mxl862xx-phylink.c |   2 +
 drivers/net/dsa/mxl862xx/mxl862xx.c         | 110 ++++-
 drivers/net/dsa/mxl862xx/mxl862xx.h         |  20 +
 6 files changed, 605 insertions(+), 29 deletions(-)

diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-fw.c b/drivers/net/dsa/mxl862xx/mxl862xx-fw.c
index 139c14adf2d9..d001a884e6fc 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-fw.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-fw.c
@@ -29,9 +29,11 @@
  *
  * STAT magics:
  *   READY  0xc55c   loader idle in the console loop        (this driver)
+ *   DL_RDY 0xc33c   loader idle in the flashless loop
  *   START  0xf48f   host   -> begin download session
  *   ACK    0xf490   loader -> START acknowledged (START + 1)
  *   END    0x3cc3   host   -> finalise now (optional, see below)
+ *   RDREG  0xe2c0   host   -> register-read command (| index), see below
  *
  * Console flash path (STAT=0xc55c) - mxl862xx_flash_firmware():
  *
@@ -71,7 +73,40 @@
  *     - never send a slice/chunk count larger than what is outstanding;
  *     - a STAT write is a command only once the loader has left the loop;
  *     - the loader leaves the count in STAT while it programs the chunk, so
- *       a lingering count does not distinguish "busy" from "verdict".
+ *       a lingering count does not distinguish "busy" from "verdict";
+ *     - interrupted-download recovery feeds 1 byte at a time (see below).
+ *
+ * Interrupted-flash recovery (mxl862xx_rescue_drain):
+ *   A host that dies mid-payload leaves the loader in the receive loop holding
+ *   STAT=0. Feed single 1-byte chunks (one DATA word + STAT=1) until r_remain
+ *   reaches 0; the loader then verifies the (now corrupt) image, publishes its
+ *   verdict and comes back to READY by itself. END is never sent here: while
+ *   r_remain is non-zero it would be consumed as a 15555-byte count, and a
+ *   lingering STAT=1 cannot be told from a chunk still being programmed.
+ *
+ * Register-read challenge (non-destructive liveness proof):
+ *   DATA := 0x7c23 (marker); STAT := 0xe2c0|idx
+ *     -> loader returns a runtime word in DATA and re-arms STAT=0xc55c.
+ *   The reply source is loader BSS, not a chip id; used only to prove a live
+ *   mailbox in mxl862xx_rescue_mode_detect().
+ *
+ * The other STAT ready magic, 0xc33c, marks the loader's flashless
+ * chip-to-chip download mode (MxL86281S 16-port tier); this driver does not
+ * use it.
+ *
+ * Rescue lifecycle (devlink): probe runs mxl862xx_rescue_mode_detect(); a
+ * wedged loader is drained back to READY by a background self-heal
+ * (rescue_heal_work), so the long recovery never holds the devlink lock.
+ * devlink dev info exposes the fw version (the "flashable" signal) only once at
+ * READY; flash_update returns -EBUSY until then, and reprobes to WSP firmware
+ * on success.
+ *
+ * Notes:
+ *   - Chip id/revision (0xc0d28884/88) are NOT reachable on this channel; they
+ *     need the clause-45 MMD firmware mailbox, which is dead under MCUboot.
+ *     Rescue identity is by SB PDI behaviour only (mxl862xx_rescue_mode_detect).
+ *   - The SMDIO PHY address comes from the device tree; the 0xe1xx register
+ *     offsets are the OTP reset defaults and the only layout supported here.
  */
 
 #include <linux/crc32.h>
@@ -104,8 +139,15 @@
 
 /* SB PDI handshake magic (published/consumed via STAT) */
 #define MXL862XX_SB_PDI_READY		0xc55c	/* loader idle, console loop */
+#define MXL862XX_SB_PDI_DL_READY	0xc33c	/* loader idle, flashless loop */
 #define MXL862XX_SB_PDI_START		0xf48f
 #define MXL862XX_SB_PDI_END		0x3cc3
+#define MXL862XX_SB_PDI_RDREG		0xe2c0	/* register-read cmd (| index) */
+#define MXL862XX_SB_PDI_RDREG_MARK	0x7c23	/* marker placed in DATA for RDREG */
+
+/* Behavioural presence probe: two distinct 16-bit latches on ADDR/DATA. */
+#define MXL862XX_SB_PDI_PROBE_A		0x5a5a
+#define MXL862XX_SB_PDI_PROBE_D		0xa5a5
 
 /* Image verification verdict published in STAT once the receive loop ends */
 #define MXL862XX_SB_PDI_VERIFY_OK	0
@@ -124,6 +166,13 @@
 #define MXL862XX_FW_WRITE_TIMEOUT_MS	60000
 #define MXL862XX_FW_REBOOT_DELAY_MS	5000
 #define MXL862XX_FW_REPROBE_DELAY_MS	500
+/* One loader mailbox step: program a 1-byte chunk or service a command */
+#define MXL862XX_SB_PDI_STEP_MS		2000
+/* Covers the loader's END wait, verification and the reset into READY */
+#define MXL862XX_SB_PDI_VERIFY_MS	15000
+/* STAT poll intervals: a mailbox step is quick, an erase is not */
+#define MXL862XX_SB_PDI_POLL_US		50
+#define MXL862XX_SB_PDI_SLOW_POLL_US	10000
 
 static int mxl862xx_sb_pdi_reset(struct mxl862xx_priv *priv)
 {
@@ -193,7 +242,8 @@ static int mxl862xx_sb_pdi_flush_last(struct mxl862xx_priv *priv,
 
 	ret = read_poll_timeout(mxl862xx_smdio_read, val,
 				val < 0 || (u16)val != (u16)data_written,
-				10000, MXL862XX_FW_WRITE_TIMEOUT_MS * 1000,
+				10000, (MXL862XX_FW_WRITE_TIMEOUT_MS +
+					MXL862XX_SB_PDI_VERIFY_MS) * 1000,
 				false, priv, MXL862XX_SB_PDI_STAT);
 	if (val < 0)
 		return val;
@@ -219,6 +269,379 @@ static void mxl862xx_flash_notify(struct devlink *dl, const char *status,
 	devlink_flash_update_status_notify(dl, status, NULL, done, total);
 }
 
+/* Byte-count of each chunk fed to the loader during drain. It MUST be 1: the
+ * loader only lets us observe "counter == 0", never "counter < step", so any
+ * step > 1 can subtract past zero, underflow the 32-bit counter and wedge the
+ * loader for ~2^32 more bytes (a state only a power cycle clears). Stepping by
+ * 1 walks the counter through every value and is guaranteed to land on zero
+ * whatever its (possibly odd) start. A 1-byte chunk is a path the loader
+ * already handles: the normal transfer ends with a single trailing byte for
+ * odd-sized images (see Step 6).
+ */
+#define MXL862XX_DRAIN_CHUNK_BYTES	1
+
+/* Log the drain's progress every so many bytes; it can run for a long time */
+#define MXL862XX_DRAIN_LOG_BYTES	(128 * 1024)
+
+/* Wait for the loader to ask for the next chunk (STAT 0) or to come back to its
+ * command loop (STAT READY), and return the STAT value either way, or
+ * -ECANCELED once teardown asks the caller to stop. On timeout the value is
+ * whatever STAT still holds, which carries no further information: the
+ * loader keeps the count we wrote visible while it programs the chunk, and that
+ * is the same value it publishes as the "image rejected" verdict once the
+ * counter reaches zero.
+ *
+ * STAT 0 is unambiguous here even though it is also the "image verified"
+ * verdict: by the r_remain == 0 rule the loader leaves the receive loop the
+ * moment the counter reaches zero, so it is never both inside the loop asking
+ * for a chunk and publishing a verdict. Once it has left, the next STAT write
+ * is a command rather than a count, so feeding one more chunk after a verdict
+ * cannot underflow anything either.
+ */
+static int mxl862xx_sb_pdi_poll_drain(struct mxl862xx_priv *priv,
+				      unsigned long sleep_us,
+				      unsigned long timeout_ms)
+{
+	int val;
+
+	read_poll_timeout(mxl862xx_smdio_read, val,
+			  val < 0 || (u16)val == MXL862XX_SB_PDI_READY ||
+			  (u16)val == 0 ||
+			  test_bit(MXL862XX_FLAG_WORK_STOPPED, &priv->flags),
+			  sleep_us, timeout_ms * 1000, false,
+			  priv, MXL862XX_SB_PDI_STAT);
+	if (val < 0)
+		return val;
+	if (test_bit(MXL862XX_FLAG_WORK_STOPPED, &priv->flags))
+		return -ECANCELED;
+	return (u16)val;
+}
+
+/* The loader is not asking for a chunk: it may still be programming the last
+ * one, or the counter has reached zero and it is verifying the image and
+ * resetting into READY. Before the first chunk it may also still be erasing
+ * for the session that died, which no verify window covers. Wait that out --
+ * STAT cannot tell the cases apart, and guessing would mean writing END into a
+ * live receive loop.
+ *
+ * Return: 0 once the loader has left the loop, -EAGAIN if it asks for another
+ * chunk after all, -EIO for a loader still holding the count when the window
+ * expires, -ECANCELED on teardown, or an SMDIO bus error.
+ */
+static int mxl862xx_rescue_drain_finish(struct mxl862xx_priv *priv, u32 chunk)
+{
+	struct device *dev = &priv->mdiodev->dev;
+	int stat;
+
+	if (chunk)
+		stat = mxl862xx_sb_pdi_poll_drain(priv, MXL862XX_SB_PDI_POLL_US,
+						  MXL862XX_SB_PDI_VERIFY_MS);
+	else
+		stat = mxl862xx_sb_pdi_poll_drain(priv,
+						  MXL862XX_SB_PDI_SLOW_POLL_US,
+						  MXL862XX_FW_ERASE_TIMEOUT_MS);
+	if (stat < 0)
+		return stat;
+	if (stat == MXL862XX_SB_PDI_READY)
+		return 0;
+	if (stat == MXL862XX_SB_PDI_VERIFY_BAD) {
+		dev_err(dev,
+			"flash: loader stuck after %u chunks, power cycle it\n",
+			chunk);
+		return -EIO;
+	}
+	if (stat) {
+		if (!chunk) {
+			dev_err(dev,
+				"flash: loader still busy after the erase window\n");
+			return -EIO;
+		}
+		/* A firmware is answering, not the loader: an image survived
+		 * in flash and booted.
+		 */
+		dev_info(dev, "flash: firmware booted while draining\n");
+		return 0;
+	}
+
+	return -EAGAIN;
+}
+
+/* Walk the loader's receive counter to zero (see the header): the image size
+ * died with the host, and a chunk larger than what is outstanding underflows
+ * the counter, so only single bytes are safe. Tens of minutes for a multi-MiB
+ * remainder. Returns 0 once the loader has left the receive loop, <0 on error;
+ * a counter an earlier oversized chunk underflowed needs a power cycle.
+ */
+static int mxl862xx_rescue_drain(struct mxl862xx_priv *priv)
+{
+	/* Bound: twice the loader's 16 MiB image cap, one byte per chunk. */
+	u32 max_chunks = 2u * (16u << 20) / MXL862XX_DRAIN_CHUNK_BYTES;
+	struct device *dev = &priv->mdiodev->dev;
+	u32 chunk = 0;
+	int ret, stat;
+
+	while (chunk < max_chunks) {
+		/* Teardown can interrupt this long drain. */
+		if (test_bit(MXL862XX_FLAG_WORK_STOPPED, &priv->flags))
+			return -ECANCELED;
+
+		stat = mxl862xx_sb_pdi_poll_drain(priv, MXL862XX_SB_PDI_POLL_US,
+						  MXL862XX_SB_PDI_STEP_MS);
+		if (stat < 0)
+			return stat;
+		if (stat == MXL862XX_SB_PDI_READY)
+			return 0;
+
+		if (stat) {
+			ret = mxl862xx_rescue_drain_finish(priv, chunk);
+			if (ret != -EAGAIN)
+				return ret;
+		}
+
+		/* Feed one zero byte; reset cleared the write latch. */
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+					   MXL862XX_SB_PDI_CTRL_WR);
+		if (ret < 0)
+			return ret;
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA, 0x0000);
+		if (ret < 0)
+			return ret;
+		ret = mxl862xx_sb_pdi_reset(priv);
+		if (ret < 0)
+			return ret;
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT,
+					   MXL862XX_DRAIN_CHUNK_BYTES);
+		if (ret < 0)
+			return ret;
+		chunk++;
+		if (!(chunk % MXL862XX_DRAIN_LOG_BYTES))
+			dev_info(dev, "flash: drained %u KiB so far\n",
+				 chunk / 1024);
+		cond_resched();
+	}
+
+	dev_err(dev,
+		"flash: interrupted download did not drain after %u chunks\n",
+		chunk);
+
+	return -ETIMEDOUT;
+}
+
+/* Background self-heal: drain a wedged download off the devlink flash path, so
+ * the long recovery never holds the devlink lock. Scheduled from probe;
+ * reprobes on success so the probe-time detection re-classifies the switch.
+ */
+void mxl862xx_rescue_heal_work_fn(struct work_struct *work)
+{
+	struct mxl862xx_priv *priv =
+		container_of(work, struct mxl862xx_priv, rescue_heal_work);
+	struct device *dev = &priv->mdiodev->dev;
+	int ret;
+
+	ret = mxl862xx_rescue_drain(priv);
+	if (ret == -ECANCELED)
+		return;
+	if (ret) {
+		/* Nothing retries this, so say so: rescue_ready stays clear
+		 * and devlink dev flash reports why it refuses.
+		 */
+		dev_err(dev, "flash: download recovery failed: %pe\n",
+			ERR_PTR(ret));
+		WRITE_ONCE(priv->rescue_failed, true);
+		return;
+	}
+
+	/* The interrupted transfer is finalised; reprobe so the probe-time
+	 * detection brings the driver up -- flashable in rescue mode if the
+	 * loader is at READY, or normally if a valid image booted. The core
+	 * skips the re-probe on its own if the device is unbound first; the
+	 * flag test only avoids scheduling one certain to be skipped. A
+	 * failed hand-off leaves nothing to reclassify the switch, so mark
+	 * recovery failed rather than promise a retry that cannot succeed.
+	 */
+	if (test_bit(MXL862XX_FLAG_WORK_STOPPED, &priv->flags))
+		return;
+
+	if (device_schedule_reprobe(dev, MXL862XX_FW_REPROBE_DELAY_MS))
+		WRITE_ONCE(priv->rescue_failed, true);
+}
+
+/* Detect MCUboot rescue mode over clause-22 SMDIO alone, so the caller can rule
+ * the loader out before any C45 API request (which only runs into its timeouts
+ * when no WSP firmware answers). A scratch write to ADDR/DATA must latch or the
+ * chip is absent (-ENODEV); the mailbox is reset first, or a transfer
+ * interrupted with CTRL=WR would take that write as a payload word instead of
+ * latching it. STAT then classifies the state, poked destructively only when 0,
+ * the one value a running firmware never holds:
+ *
+ *  - 0xc33c: flashless loop; recognised but not supported here.
+ *  - 0xc55c: console loop, if the register-read challenge is serviced.
+ *  - 0xf48f/0xf490: a download handshake nobody can finish; rescue, but only
+ *    a power cycle gets the loader out of it.
+ *  - other non-zero: running firmware, left unpoked. With @settle the loader
+ *    gets one step to publish 0 or READY first, and a count outliving that is
+ *    a busy loader, for a caller which has ruled a running firmware out.
+ *  - 0: wedged receive loop; the 1-byte slice-advance then says whether it
+ *    still needs draining or has just finished.
+ *
+ * The scratch write reaches a running firmware too, but lands in mailbox
+ * registers it does not read, so it is inert there.
+ *
+ * Return: MXL862XX_IN_RESCUE, MXL862XX_NOT_RESCUE, -ENODEV when the scratch
+ * write does not latch, which is a switch that does not answer at all or one
+ * whose SB PDI window is not at the offsets above, -EOPNOTSUPP for the
+ * flashless loop, -ENXIO for a READY loader whose mailbox fails the challenge,
+ * -ECANCELED when teardown interrupts a poll, or an SMDIO bus error.
+ */
+int mxl862xx_rescue_mode_detect(struct mxl862xx_priv *priv, bool settle)
+{
+	int stat, dat, ret, rb, a, d;
+
+	/* rescue_ready gates flashing; a wedged loader needs the drain first. */
+	WRITE_ONCE(priv->rescue_ready, false);
+
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		return ret;
+
+	/* Presence: a live chip latches the scratch write, an absent one floats. */
+	a = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_ADDR,
+				 MXL862XX_SB_PDI_PROBE_A);
+	if (a < 0)
+		return a;
+	d = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA,
+				 MXL862XX_SB_PDI_PROBE_D);
+	if (d < 0)
+		return d;
+	a = mxl862xx_smdio_read(priv, MXL862XX_SB_PDI_ADDR);
+	if (a < 0)
+		return a;
+	d = mxl862xx_smdio_read(priv, MXL862XX_SB_PDI_DATA);
+	if (d < 0)
+		return d;
+	if ((u16)a != MXL862XX_SB_PDI_PROBE_A ||
+	    (u16)d != MXL862XX_SB_PDI_PROBE_D)
+		return -ENODEV;
+
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		return ret;
+
+	stat = mxl862xx_smdio_read(priv, MXL862XX_SB_PDI_STAT);
+	if (stat < 0)
+		return stat;
+
+	/* Flashless-download loop (MxL86281S tier): this driver does not
+	 * support it -- the console flash path expects READY. Treat it as an
+	 * unusable configuration, like any other unsupported state.
+	 */
+	if ((u16)stat == MXL862XX_SB_PDI_DL_READY)
+		return -EOPNOTSUPP;
+
+	/* Console loop at READY: confirm the live mailbox with the register-read
+	 * challenge (consumes the marker from DATA and re-arms READY).
+	 */
+	if ((u16)stat == MXL862XX_SB_PDI_READY) {
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA,
+					   MXL862XX_SB_PDI_RDREG_MARK);
+		if (ret < 0)
+			return ret;
+		ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT,
+					   MXL862XX_SB_PDI_RDREG);
+		if (ret < 0)
+			return ret;
+		rb = mxl862xx_sb_pdi_poll_stat(priv, MXL862XX_SB_PDI_READY,
+					       MXL862XX_SB_PDI_STEP_MS);
+		dat = mxl862xx_smdio_read(priv, MXL862XX_SB_PDI_DATA);
+		ret = mxl862xx_sb_pdi_reset(priv);
+		/* Never re-arming READY fails the challenge like any other
+		 * unserviced command; report it as such rather than as a bus
+		 * timeout the bus never saw.
+		 */
+		if (rb == -ETIMEDOUT)
+			rb = -ENXIO;
+		if (rb < 0)
+			return rb;
+		if (dat < 0)
+			return dat;
+		if (ret < 0)
+			return ret;
+		if ((u16)dat != MXL862XX_SB_PDI_RDREG_MARK) {
+			WRITE_ONCE(priv->rescue_ready, true);
+			return MXL862XX_IN_RESCUE;
+		}
+		/* READY but the marker is untouched, so nothing is servicing the
+		 * mailbox. A firmware publishing 0xc55c as its status word looks
+		 * exactly like this, and flashing one would be far worse than
+		 * refusing to bind, so treat it as unusable.
+		 */
+		return -ENXIO;
+	}
+
+	/* The download handshake lives in STAT too and outlives a mailbox
+	 * reset, so an aborted transfer leaves the loader waiting for a
+	 * header no later session can supply: only a power cycle clears it.
+	 */
+	if ((u16)stat == MXL862XX_SB_PDI_START ||
+	    (u16)stat == MXL862XX_SB_PDI_START + 1) {
+		WRITE_ONCE(priv->rescue_failed, true);
+		return MXL862XX_IN_RESCUE;
+	}
+
+	/* Any other non-zero value is a running firmware, not a loader -- but
+	 * the loader also holds the count of a chunk it is programming or
+	 * erasing for, so let a caller that has ruled the firmware out wait a
+	 * step for the next state; a count outliving that is that busy loader.
+	 */
+	if (stat) {
+		if (!settle)
+			return MXL862XX_NOT_RESCUE;
+
+		stat = mxl862xx_sb_pdi_poll_drain(priv, MXL862XX_SB_PDI_POLL_US,
+						  MXL862XX_SB_PDI_STEP_MS);
+		if (stat < 0)
+			return stat;
+		if (stat == MXL862XX_SB_PDI_READY) {
+			WRITE_ONCE(priv->rescue_ready, true);
+			return MXL862XX_IN_RESCUE;
+		}
+		if (stat)
+			return MXL862XX_IN_RESCUE;
+	}
+
+	/* STAT == 0: a wedged receive loop takes a 1-byte slice-advance (feed
+	 * one DATA word first, like a drain chunk) and asks for the next chunk
+	 * by publishing 0 again. Had that byte been the last one outstanding,
+	 * the loader leaves the loop instead and returns to READY, having
+	 * consumed the advance -- proof enough of a live mailbox to skip the
+	 * challenge. Anything else means it is still working on it. All three
+	 * are rescue, so this never fails probe; only the drain does.
+	 */
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_CTRL,
+				   MXL862XX_SB_PDI_CTRL_WR);
+	if (ret < 0)
+		return ret;
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_DATA, 0x0000);
+	if (ret < 0)
+		return ret;
+	ret = mxl862xx_sb_pdi_reset(priv);
+	if (ret < 0)
+		return ret;
+	ret = mxl862xx_smdio_write(priv, MXL862XX_SB_PDI_STAT,
+				   MXL862XX_DRAIN_CHUNK_BYTES);
+	if (ret < 0)
+		return ret;
+
+	rb = mxl862xx_sb_pdi_poll_drain(priv, MXL862XX_SB_PDI_POLL_US,
+					MXL862XX_SB_PDI_STEP_MS);
+	if (rb < 0)
+		return rb;
+	if (rb == MXL862XX_SB_PDI_READY)
+		WRITE_ONCE(priv->rescue_ready, true);
+
+	return MXL862XX_IN_RESCUE;
+}
+
 /* MCUboot firmware image header */
 struct mxl862xx_fw_hdr {
 	__le32 image_type;
@@ -294,13 +717,15 @@ static int mxl862xx_flash_firmware(struct mxl862xx_priv *priv,
 	int ret, i;
 
 	/* Step 1: reboot the firmware into MCUboot rescue mode */
-	ret = mxl862xx_api_wrap(priv, SYS_MISC_FW_UPDATE, NULL, 0,
-				false, false);
-	if (ret) {
-		dev_err(&priv->mdiodev->dev,
-			"flash: FW_UPDATE command failed: %pe\n",
-			ERR_PTR(ret));
-		return ret;
+	if (!READ_ONCE(priv->rescue_mode)) {
+		ret = mxl862xx_api_wrap(priv, SYS_MISC_FW_UPDATE, NULL, 0,
+					false, false);
+		if (ret) {
+			dev_err(&priv->mdiodev->dev,
+				"flash: FW_UPDATE command failed: %pe\n",
+				ERR_PTR(ret));
+			return ret;
+		}
 	}
 
 	/* Step 2: wait for bootloader ready */
@@ -487,6 +912,25 @@ int mxl862xx_devlink_info_get(struct dsa_switch *ds,
 	char buf[16];
 	int ret;
 
+	/* No chip-id/revision in MCUboot (needs the firmware MMD mailbox). The
+	 * fw version doubles as the "ready to flash" signal: report it only
+	 * once the loader is at a clean READY, nothing while still draining.
+	 */
+	if (READ_ONCE(priv->rescue_mode)) {
+		if (!READ_ONCE(priv->rescue_ready))
+			return 0;
+
+		snprintf(buf, sizeof(buf), "%u.%u.%u",
+			 priv->fw_version.major, priv->fw_version.minor,
+			 priv->fw_version.revision);
+		ret = devlink_info_version_running_put(req,
+				DEVLINK_INFO_VERSION_GENERIC_FW, buf);
+		if (ret)
+			return ret;
+		return devlink_info_version_stored_put(req,
+				DEVLINK_INFO_VERSION_GENERIC_FW, buf);
+	}
+
 	/* A 0 part number means the CHIP ID read failed or the part is
 	 * unfused; omit it rather than publish a bogus "0000" that fwupd
 	 * would match firmware against -- it then falls back to the driver
@@ -565,9 +1009,27 @@ int mxl862xx_devlink_flash_update(struct dsa_switch *ds,
 		return ret;
 	}
 
-	dev_info(ds->dev, "flash: running firmware %u.%u.%u\n",
-		 priv->fw_version.major, priv->fw_version.minor,
-		 priv->fw_version.revision);
+	/* Refuse to flash while the background self-heal is still draining, and
+	 * for good once it has given up on the loader.
+	 */
+	if (READ_ONCE(priv->rescue_failed)) {
+		NL_SET_ERR_MSG_MOD(extack, "download recovery failed");
+		return -EIO;
+	}
+
+	if (READ_ONCE(priv->rescue_mode) && !READ_ONCE(priv->rescue_ready)) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "switch is recovering an interrupted download");
+		return -EBUSY;
+	}
+
+	if (READ_ONCE(priv->rescue_mode))
+		dev_info(ds->dev,
+			 "flash: flashing switch via MCUboot rescue mode\n");
+	else
+		dev_info(ds->dev, "flash: running firmware %u.%u.%u\n",
+			 priv->fw_version.major, priv->fw_version.minor,
+			 priv->fw_version.revision);
 
 	/* Close ports while the firmware is still alive so the DSA core's
 	 * MDB/FDB tracking is drained, and detach user ports so userspace
@@ -614,6 +1076,7 @@ int mxl862xx_devlink_flash_update(struct dsa_switch *ds,
 		 * readiness poll below read the freshly booted firmware.
 		 */
 		priv->flash_owner = current;
+		WRITE_ONCE(priv->rescue_mode, false);
 		mutex_unlock(&priv->mdiodev->bus->mdio_lock);
 
 		/* Refresh the cached versions so the flash update only
@@ -630,11 +1093,13 @@ int mxl862xx_devlink_flash_update(struct dsa_switch *ds,
 	if (ret) {
 		/* The switch is in MCUboot with erased or partly written flash;
 		 * drop the cached identity so devlink dev info stops reporting
-		 * the pre-flash version until the reprobe re-reads the truth.
+		 * the pre-flash version until the reprobe re-reads the truth,
+		 * and with it the loader's clean READY state.
 		 */
 		memset(&priv->fw_version, 0, sizeof(priv->fw_version));
 		priv->asic_id = 0;
 		priv->asic_rev = 0;
+		WRITE_ONCE(priv->rescue_ready, false);
 	}
 
 	mutex_lock_nested(&priv->mdiodev->bus->mdio_lock, MDIO_MUTEX_NESTED);
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-fw.h b/drivers/net/dsa/mxl862xx/mxl862xx-fw.h
index 15ed3a46bcfe..02e5a627e947 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-fw.h
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-fw.h
@@ -6,7 +6,10 @@
 #include <net/dsa.h>
 
 struct mxl862xx_priv;
+struct work_struct;
 
+int mxl862xx_rescue_mode_detect(struct mxl862xx_priv *priv, bool settle);
+void mxl862xx_rescue_heal_work_fn(struct work_struct *work);
 int mxl862xx_devlink_info_get(struct dsa_switch *ds,
 			      struct devlink_info_req *req,
 			      struct netlink_ext_ack *extack);
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-host.c b/drivers/net/dsa/mxl862xx/mxl862xx-host.c
index 4b3956a518cf..694c22d2dd09 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-host.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-host.c
@@ -17,6 +17,7 @@
 #include <net/dsa.h>
 #include "mxl862xx.h"
 #include "mxl862xx-cmd.h"
+#include "mxl862xx-fw.h"
 #include "mxl862xx-host.h"
 
 #define CTRL_BUSY_MASK			BIT(15)
@@ -347,6 +348,11 @@ int mxl862xx_api_wrap(struct mxl862xx_priv *priv, u16 cmd, void *_data,
 		goto out;
 	}
 
+	if (priv->rescue_mode) {
+		ret = -ENODEV;
+		goto out;
+	}
+
 	/* During the post-flash readiness poll block_host stays set, but the
 	 * flash path's own firmware version reads must reach the new image;
 	 * host writes stay blocked so stale resource IDs cannot corrupt it.
@@ -558,9 +564,11 @@ int mxl862xx_smdio_write(struct mxl862xx_priv *priv, u32 addr, u16 val)
 void mxl862xx_host_init(struct mxl862xx_priv *priv)
 {
 	INIT_WORK(&priv->crc_err_work, mxl862xx_crc_err_work_fn);
+	INIT_WORK(&priv->rescue_heal_work, mxl862xx_rescue_heal_work_fn);
 }
 
 void mxl862xx_host_shutdown(struct mxl862xx_priv *priv)
 {
 	cancel_work_sync(&priv->crc_err_work);
+	cancel_work_sync(&priv->rescue_heal_work);
 }
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx-phylink.c b/drivers/net/dsa/mxl862xx/mxl862xx-phylink.c
index b689652aa9b9..6fde3a58939d 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx-phylink.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx-phylink.c
@@ -406,6 +406,8 @@ mxl862xx_phylink_mac_select_pcs(struct phylink_config *config,
 
 	switch (port) {
 	case 9 ... 16:
+		if (READ_ONCE(priv->rescue_mode))
+			return NULL;
 		if (!MXL862XX_FW_VER_MIN(priv, 1, 0, 84)) {
 			dev_warn_once(dp->ds->dev,
 				      "SerDes PCS unsupported on old firmware.\n");
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx.c b/drivers/net/dsa/mxl862xx/mxl862xx.c
index 5668aac9ef7a..d5e29fd74adb 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx.c
+++ b/drivers/net/dsa/mxl862xx/mxl862xx.c
@@ -667,27 +667,85 @@ static void mxl862xx_free_bridge(struct dsa_switch *ds,
 	priv->bridges[bridge->num] = 0;
 }
 
+static void mxl862xx_setup_rescue(struct dsa_switch *ds)
+{
+	struct mxl862xx_priv *priv = ds->priv;
+
+	if (priv->rescue_ready) {
+		dev_warn(ds->dev,
+			 "switch in MCUboot rescue mode, use devlink to flash new firmware\n");
+		return;
+	}
+
+	if (priv->rescue_failed) {
+		dev_warn(ds->dev,
+			 "switch in MCUboot with an unfinishable download, power cycle it\n");
+		return;
+	}
+
+	/* Drain the wedged download in the background so it never holds the
+	 * devlink lock; info and flash become available once ready.
+	 */
+	dev_warn(ds->dev,
+		 "switch in MCUboot with an interrupted download, recovering in background\n");
+	queue_work(system_long_wq, &priv->rescue_heal_work);
+}
+
 static int mxl862xx_setup(struct dsa_switch *ds)
 {
 	struct mxl862xx_priv *priv = ds->priv;
 	int n_user_ports = 0, max_vlans;
 	int ingress_finals, vid_rules;
 	struct dsa_port *dp;
-	int ret, i;
+	int ret, i, rescue;
 
-	ret = mxl862xx_reset(priv);
-	if (ret)
-		return ret;
+	/* Detect the loader over SB PDI first: it needs no firmware, unlike the
+	 * C45 API (mxl862xx_reset/wait_ready), which spends its whole 10 s
+	 * window on a mailbox nobody answers. Touch C45 only once rescue is
+	 * ruled out.
+	 */
+	rescue = mxl862xx_rescue_mode_detect(priv, false);
+	if (rescue < 0) {
+		dev_err(ds->dev, "switch state detection failed: %pe\n",
+			ERR_PTR(rescue));
+		return rescue;
+	}
 
-	ret = mxl862xx_wait_ready(ds);
-	if (ret)
-		return ret;
+	if (rescue == MXL862XX_NOT_RESCUE) {
+		ret = mxl862xx_reset(priv);
+		if (ret)
+			return ret;
+
+		ret = mxl862xx_wait_ready(ds);
+		if (ret) {
+			/* the reset may only now have triggered rescue mode */
+			rescue = mxl862xx_rescue_mode_detect(priv, true);
+			if (rescue < 0) {
+				dev_err(ds->dev,
+					"switch not responding after reset: %pe\n",
+					ERR_PTR(rescue));
+				return rescue;
+			}
+			if (rescue == MXL862XX_NOT_RESCUE)
+				return ret;
+		}
+	}
+
+	priv->rescue_mode = rescue;
 
+	/* Software-only SerDes state, needed before anything can reach phylink,
+	 * including a rescue-mode flash clearing rescue_mode ahead of reprobe.
+	 */
 	mutex_init(&priv->serdes_lock);
 	for (i = 0; i < ARRAY_SIZE(priv->serdes_ports); i++)
 		mxl862xx_setup_pcs(priv, &priv->serdes_ports[i],
 				   i + MXL862XX_FIRST_SERDES_PORT);
 
+	if (priv->rescue_mode) {
+		mxl862xx_setup_rescue(ds);
+		return 0;
+	}
+
 	/* Calculate Extended VLAN block sizes.
 	 * With VLAN Filter handling VID membership checks:
 	 *   Ingress: only final catchall rules (PVID insertion, 802.1Q
@@ -766,11 +824,21 @@ static int mxl862xx_port_state(struct dsa_switch *ds, int port, bool enable)
 static int mxl862xx_port_enable(struct dsa_switch *ds, int port,
 				struct phy_device *phydev)
 {
+	struct mxl862xx_priv *priv = ds->priv;
+
+	if (READ_ONCE(priv->rescue_mode))
+		return 0;
+
 	return mxl862xx_port_state(ds, port, true);
 }
 
 static void mxl862xx_port_disable(struct dsa_switch *ds, int port)
 {
+	struct mxl862xx_priv *priv = ds->priv;
+
+	if (READ_ONCE(priv->rescue_mode))
+		return;
+
 	if (mxl862xx_port_state(ds, port, false))
 		dev_err(ds->dev, "failed to disable port %d\n", port);
 }
@@ -1388,6 +1456,17 @@ static int mxl862xx_port_setup(struct dsa_switch *ds, int port)
 	bool is_cpu_port = dsa_port_is_cpu(dp);
 	int ret;
 
+	if (dsa_port_is_dsa(dp)) {
+		dev_err(ds->dev, "port %d: DSA links not supported\n", port);
+		return -EOPNOTSUPP;
+	}
+
+	/* DSA reinits failed user ports as unused; shared ports must
+	 * succeed for the tree to register.
+	 */
+	if (READ_ONCE(priv->rescue_mode))
+		return dsa_port_is_user(dp) ? -ENODEV : 0;
+
 	ret = mxl862xx_port_state(ds, port, false);
 	if (ret)
 		return ret;
@@ -1397,11 +1476,6 @@ static int mxl862xx_port_setup(struct dsa_switch *ds, int port)
 	if (dsa_port_is_unused(dp))
 		return 0;
 
-	if (dsa_port_is_dsa(dp)) {
-		dev_err(ds->dev, "port %d: DSA links not supported\n", port);
-		return -EOPNOTSUPP;
-	}
-
 	ret = mxl862xx_configure_sp_tag_proto(ds, port, is_cpu_port);
 	if (ret)
 		return ret;
@@ -1623,11 +1697,12 @@ static int mxl862xx_port_mdb_del(struct dsa_switch *ds, int port,
 	ether_addr_copy(qparam.mac, mdb->addr);
 
 	ret = MXL862XX_API_READ(priv, MXL862XX_MAC_TABLEENTRYQUERY, qparam);
-	/* Post-flash teardown: the firmware and its MAC table are gone, so
-	 * there is nothing left to delete. Outside it, -ENODEV is a bus error
-	 * and must be reported.
+	/* Post-flash teardown or MCUboot: the firmware and its MAC table are
+	 * gone, so there is nothing left to delete. Outside those, -ENODEV is a
+	 * bus error and must be reported.
 	 */
-	if (ret == -ENODEV && priv->skip_teardown)
+	if (ret == -ENODEV &&
+	    (priv->skip_teardown || READ_ONCE(priv->rescue_mode)))
 		return 0;
 	if (ret)
 		return ret;
@@ -1685,6 +1760,9 @@ static void mxl862xx_port_stp_state_set(struct dsa_switch *ds, int port,
 	struct mxl862xx_priv *priv = ds->priv;
 	int ret;
 
+	if (READ_ONCE(priv->rescue_mode))
+		return;
+
 	switch (state) {
 	case BR_STATE_DISABLED:
 		param.port_state = cpu_to_le32(MXL862XX_STP_PORT_STATE_DISABLE);
diff --git a/drivers/net/dsa/mxl862xx/mxl862xx.h b/drivers/net/dsa/mxl862xx/mxl862xx.h
index 2d38885ecfda..4ed2fd5cbca7 100644
--- a/drivers/net/dsa/mxl862xx/mxl862xx.h
+++ b/drivers/net/dsa/mxl862xx/mxl862xx.h
@@ -4,7 +4,9 @@
 #define __MXL862XX_H
 
 #include <asm/byteorder.h>
+#include <linux/bitops.h>
 #include <linux/mdio.h>
+#include <linux/mutex.h>
 #include <linux/workqueue.h>
 #include <net/dsa.h>
 
@@ -14,6 +16,10 @@ struct mxl862xx_priv;
 #define MXL862XX_FIRST_SERDES_PORT	9
 #define MXL862XX_SERDES_SLOTS		4
 
+/* mxl862xx_rescue_mode_detect() return codes (negative values are errors) */
+#define MXL862XX_NOT_RESCUE		0
+#define MXL862XX_IN_RESCUE		1
+
 #define MXL862XX_DEFAULT_BRIDGE		0
 #define MXL862XX_MAX_BRIDGES		48
 #define MXL862XX_MAX_BRIDGE_PORTS	128
@@ -332,6 +338,16 @@ struct mxl862xx_fw_version {
  * @shutting_down:      set under the devlink instance lock once ->shutdown()
  *                      has begun, so no flash starts while the system is
  *                      going down
+ * @rescue_mode:        switch is in MCUboot; firmware API commands fail fast,
+ *                      only clause-22 SMDIO works. Set from setup() before the
+ *                      switch is registered and cleared with WRITE_ONCE() under
+ *                      the MDIO bus lock for the benefit of mxl862xx_api_wrap();
+ *                      readers outside that lock use READ_ONCE().
+ * @rescue_ready:       (rescue_mode) loader is at a clean READY and will accept
+ *                      a flash; false while rescue_heal_work is draining
+ * @rescue_failed:      (rescue_mode) the self-heal gave up or cannot run; the
+ *                      loader needs a power cycle and no flash can be accepted
+ * @rescue_heal_work:   background self-heal draining a wedged download to READY
  * @stats_work:         periodic work item that polls RMON hardware counters
  *                      and accumulates them into 64-bit per-port stats
  */
@@ -339,6 +355,7 @@ struct mxl862xx_priv {
 	struct dsa_switch *ds;
 	struct mdio_device *mdiodev;
 	struct work_struct crc_err_work;
+	struct work_struct rescue_heal_work;
 	unsigned long flags;
 	u16 drop_meter;
 	struct mxl862xx_fw_version fw_version;
@@ -356,6 +373,9 @@ struct mxl862xx_priv {
 	bool block_host;
 	bool skip_teardown;
 	bool shutting_down;
+	bool rescue_mode;
+	bool rescue_ready;
+	bool rescue_failed;
 	struct delayed_work stats_work;
 };
 
-- 
2.55.0

[PATCH net-next v16 6/6] net: dsa: mxl862xx: document devlink flash and info support

[Daniel Golle]

Describe the devlink info versions and the flash update behaviour,
including the MCUboot rescue mode recovery, in a dedicated file under
Documentation/networking/devlink/ and link it from the index. Add the
new file to the driver's MAINTAINERS entry.

Assisted-by: LLM
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
v16:
 - document that a reboot waits for a running flash and that one
   requested afterwards is refused, and that a bus error ends the
   download recovery for good
 - title-case the "Flash Update" heading, as the other devlink driver
   documents do
 - say that the ports come back down from a flash, that a reprobe which
   cannot be scheduled needs a rebind, and which of the two recovery
   failures needs a power cycle and which a rebind (found by Sashiko AI
   review)

v15:
 - asic.rev is read from the CHIP ID registers as well, not from one
   register word shared with asic.id (found by Sashiko AI review)
 - -EIO says the driver gave up on the recovery, which may need a driver
   rebind rather than a power cycle, and an interrupted opening
   handshake is reported the same way (found by Sashiko AI review)

v14: no changes

v13: no changes

v12: no changes

v11: no changes

v10: document that a switch power cycled on its own needs the driver
     unbound and rebound before a failed recovery is re-examined

v9: no changes, picked up Andrew's v5 Reviewed-by

v8:
 - asic.id and asic.rev are omitted whenever the part number reads
   zero, not only in MCUboot rescue mode (found by Sashiko AI review)
 - drop the claim that "0.0.0" marks a switch that never ran firmware;
   rescue mode always reports it (found by Sashiko AI review)
 - document devlink dev flash as the signal that says whether a
   recovery is still running, including the -EIO it returns once the
   recovery has failed (found by Sashiko AI review)

v7: no changes

v6: no changes

v5: new patch, splitting the devlink documentation out of the flash
    update and rescue mode recovery patches so each keeps to code
    (Jakub Kicinski asked for the documentation)

 Documentation/networking/devlink/index.rst    |  1 +
 Documentation/networking/devlink/mxl862xx.rst | 91 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 3 files changed, 93 insertions(+)
 create mode 100644 Documentation/networking/devlink/mxl862xx.rst

diff --git a/Documentation/networking/devlink/index.rst b/Documentation/networking/devlink/index.rst
index d4a83fdcff7f..145cb8a4becf 100644
--- a/Documentation/networking/devlink/index.rst
+++ b/Documentation/networking/devlink/index.rst
@@ -95,6 +95,7 @@ parameters, info versions, and other features it supports.
    mlx5
    mlxsw
    mv88e6xxx
+   mxl862xx
    netdevsim
    nfp
    octeontx2
diff --git a/Documentation/networking/devlink/mxl862xx.rst b/Documentation/networking/devlink/mxl862xx.rst
new file mode 100644
index 000000000000..793f3521f505
--- /dev/null
+++ b/Documentation/networking/devlink/mxl862xx.rst
@@ -0,0 +1,91 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+mxl862xx devlink support
+========================
+
+This document describes the devlink features implemented by the
+``mxl862xx`` device driver.
+
+Info versions
+=============
+
+The ``mxl862xx`` driver reports the following versions
+
+.. list-table:: devlink info versions implemented
+   :widths: 5 5 5 85
+
+   * - Name
+     - Type
+     - Example
+     - Description
+   * - ``asic.id``
+     - fixed
+     - 8628
+     - The chip part number read from the CHIP ID registers. Omitted
+       when the part number reads as zero, which happens for a switch
+       sitting in MCUboot rescue mode (the registers need a running
+       firmware), for an unfused part, and after a failed flash.
+   * - ``asic.rev``
+     - fixed
+     - 0
+     - The chip version, read from the CHIP ID registers as well. Both
+       values are published behind the same check, so it is omitted
+       whenever ``asic.id`` is.
+   * - ``fw``
+     - running, stored
+     - 1.0.70
+     - Version of the firmware running on the switch, reported as both
+       running and stored since the switch boots it from its own flash.
+       It is omitted while no firmware version is known: after a failed
+       flash, and in MCUboot rescue mode while an interrupted download
+       is still being recovered in the background. Once the loader is
+       ready to accept a new image the version appears as "0.0.0",
+       which no released firmware reports, so version-comparing tools
+       offer any available release as an upgrade. Use ``devlink dev
+       flash`` to tell a recovering switch from a ready one, see below;
+       a missing version on its own does not say why.
+
+Flash Update
+============
+
+The ``mxl862xx`` driver implements support for ``devlink dev flash``.
+The signed firmware image is transferred to the switch over the same
+MDIO bus which is also used to manage the switch, then verified and
+installed by the MCUboot bootloader running on the switch. All ports
+of the switch are closed for the duration of the update and the driver
+reprobes the switch after it has rebooted into the new firmware; they
+come back registered but down, so userspace brings them up again. A
+complete flash and reprobe cycle takes about one minute. In the rare
+case that the reprobe cannot be scheduled at all, ``devlink dev
+flash`` reports that error and the driver stays bound to a switch it
+no longer tracks until it is unbound and rebound. A reboot started
+while an update is running waits for the transfer to finish, and an
+update requested after the system has begun shutting down is refused
+with ``-ENODEV``.
+
+A switch stuck in MCUboot rescue mode, e.g. after an interrupted
+update, is registered without user ports. If the previous download was
+interrupted mid-transfer the loader is wedged; the driver drains it
+back to a clean ready state in the background, one byte at a time,
+which takes tens of minutes for a large image and is reported through
+the kernel log as it progresses. During that recovery ``devlink dev
+flash`` returns ``-EBUSY`` with an extack message saying so, and
+``devlink dev info`` reports no firmware version. Once the loader is
+ready the firmware version appears and flashing a firmware image
+through the regular update flow recovers the switch.
+
+If the driver gives up on the recovery, ``devlink dev flash`` returns
+``-EIO`` and says so in its extack message. The drain runs once and is
+never resumed, so a failed MDIO transaction ends it as well. A loader
+that stops answering the drain needs a power cycle; a completed drain
+whose reprobe could not be scheduled, and a drain a bus error cut
+short, need only a driver rebind. The driver re-examines the switch
+when it binds and at no other time, so a power cycle on a board where
+the switch can be cycled on its own still has to be followed by an
+unbind and rebind for the recovered switch to be recognised.
+
+A download interrupted during its opening handshake, before the image
+header reached the loader, is reported the same way. The loader waits
+for a header that no later session can supply, so that state needs a
+power cycle.
diff --git a/MAINTAINERS b/MAINTAINERS
index 0e04d92d1b09..43137dee4331 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16248,6 +16248,7 @@ M:	Daniel Golle <daniel@makrotopia.org>
 L:	netdev@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/net/dsa/maxlinear,mxl862xx.yaml
+F:	Documentation/networking/devlink/mxl862xx.rst
 F:	drivers/net/dsa/mxl862xx/
 F:	net/dsa/tag_mxl862xx.c
 
-- 
2.55.0