[PATCH v3 0/7] Add Allwinner A523 message box and XuanTie E906 remoteproc support

[Tim Michals <tcmichals@gmail.com>]

This series adds a driver for the message box of the Allwinner A523,
A527 and T527 (sun55i) and a remoteproc driver for their T-Head XuanTie
E906 RISC-V core, with bindings, DT nodes and KUnit tests.

v2: https://lore.kernel.org/linux-sunxi/20260927002021.797069-1-tcmichals@gmail.com/

Changes in v3 (details in each patch):
  - Message box: all four banks are clocked and out of reset (an
    unclocked bank drops writes). The FIFO is drained before its pending
    bit is cleared, and messages are delivered after the controller lock
    is dropped. A kick is done once the receiver's FIFO has room; a full
    FIFO is never written, and in poll mode the check and the write are
    under one lock. The shared reset is never asserted, as in
    sun6i-msgbox: the other banks carry traffic between the other
    processors. allwinner,tx-done-irq selects the receiver bank's write
    interrupt instead of the 1 ms poll. OMAP's ti,mbox-send-noirq is the
    same kind of per-mailbox switch, in the other direction: it turns
    the TX interrupt off for the WkupM3.
  - Remoteproc: one mailbox channel; the receive callback is deferred to
    an ordered workqueue; address translation covers only the two SRAM
    windows; debug reset and power domains added; all register regions,
    clocks and resets are required, the mailbox is optional. Carveouts
    and crash dump segments are registered in parse_fw(), and crash
    dumps contain both SRAMs and the carveouts.
  - Bindings: fixed lists for reg, clocks, resets and interrupts;
    "schema" dropped from the subjects (Krzysztof). All four message box
    interrupts are required: every A523 has them. The DSP and CPUS
    message box bank addresses were swapped in v2 and are fixed. The
    SRAMs are named as in the T527 manual (sram-a3-0, sram-a3-1).
  - KUnit patches moved after the drivers. Both suites redirect register
    access with static stubs to mocks, so they run on any architecture,
    UML included. Patches 6 and 7 only add tests and can be dropped or
    taken separately.
  - Rebased on next-20261030.

Notes for review:
  - The remap register (0x07010364, PRCM) is shared with the DSP: bit 1
    shares the 512 KiB SRAM A3_2 with the E906's subsystem, bit 0
    belongs to the DSP. The driver maps only this register and
    read-modify-writes bit 1, which is safe while no other Linux driver
    writes it. I can move it to a syscon or the R-CCU, or describe SRAM
    A3_2 through the sunxi SRAM driver (allwinner,sram), if preferred.
  - memory-region index 0 is the virtio DMA pool, then dram and trace,
    as in the TI K3 and MediaTek SCP bindings.
  - The optional crash interrupt is supported by the driver but not
    wired in any DT and not tested on hardware; the A523 has no
    dedicated line for it and the vendor BSP has none.
  - System suspend is not supported: the E906 runs next to a Linux that
    stays up, so the driver has no PM callbacks.
  - Merging: patches 1, 2 and 6 are for the mailbox tree, 3, 4 and 7
    for remoteproc, and 5 for sunxi. Patch 5 needs the bindings in
    patches 1 and 3.

Testing on a Radxa Cubie A5E (A527), Linux 7.1 PREEMPT_RT and PREEMPT
with the same driver and test files:
  - KUnit: 37/37 message box, 26/26 remoteproc, built in and as
    modules. Under UML on x86_64 one message box test is skipped (it
    needs SMP or spinlock debugging).
  - rpmsg ping (10000 messages, about 167 us round trip) and stress
    (100000 messages, 16 in flight, no loss), with vrings in DRAM and in
    SRAM, TX done by poll and by write interrupt, and message box
    unbind/bind with the remoteproc driver unbound. One interrupt per
    message.
  - The same tests with PROVE_LOCKING and DEBUG_ATOMIC_SLEEP (and
    PROVE_RAW_LOCK_NESTING on PREEMPT): no lockdep or sleep-in-atomic
    report.
  - On next-20261030: W=1 build of each patch with GCC and clang, built
    in and as modules, dt_binding_check and dtbs_check are clean;
    checkpatch --strict reports only "does MAINTAINERS need updating?"
    for the new files, which the entries added in patches 2 and 4 cover.

Tools: I used Claude Code (Anthropic) to help review the code against
the v2 comments, write the KUnit tests, run the board tests and draft
commit messages. I reviewed every change; all tests above ran on my
board.

Thanks to Krzysztof Kozlowski, Chen-Yu Tsai and Rob Herring for
reviewing v1 and v2.

Tim Michals (7):
  dt-bindings: mailbox: Add Allwinner A523 message box
  mailbox: sun55i: Add Allwinner A523 message box driver
  dt-bindings: remoteproc: Add Allwinner A523 RISC-V remote processor
  remoteproc: sunxi: Add Allwinner A523 XuanTie E906 driver
  arm64: dts: allwinner: a523: Add message box and remoteproc nodes
  mailbox: sun55i: Add KUnit tests
  remoteproc: sunxi: Add KUnit tests

 .../mailbox/allwinner,sun55i-a523-msgbox.yaml |  146 ++
 .../allwinner,sun55i-a523-rproc.yaml          |  146 ++
 MAINTAINERS                                   |   15 +
 .../arm64/boot/dts/allwinner/sun55i-a523.dtsi |   47 +
 drivers/mailbox/Kconfig                       |   24 +
 drivers/mailbox/Makefile                      |    3 +
 drivers/mailbox/sun55i-msgbox.c               |  613 ++++++++
 drivers/mailbox/sun55i-msgbox.h               |   95 ++
 drivers/mailbox/sun55i_msgbox_kunit.c         | 1387 +++++++++++++++++
 drivers/remoteproc/Kconfig                    |   26 +
 drivers/remoteproc/Makefile                   |    2 +
 drivers/remoteproc/sunxi_rproc.c              |  855 ++++++++++
 drivers/remoteproc/sunxi_rproc.h              |  124 ++
 drivers/remoteproc/sunxi_rproc_kunit.c        | 1314 ++++++++++++++++
 14 files changed, 4797 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/allwinner,sun55i-a523-msgbox.yaml
 create mode 100644 Documentation/devicetree/bindings/remoteproc/allwinner,sun55i-a523-rproc.yaml
 create mode 100644 drivers/mailbox/sun55i-msgbox.c
 create mode 100644 drivers/mailbox/sun55i-msgbox.h
 create mode 100644 drivers/mailbox/sun55i_msgbox_kunit.c
 create mode 100644 drivers/remoteproc/sunxi_rproc.c
 create mode 100644 drivers/remoteproc/sunxi_rproc.h
 create mode 100644 drivers/remoteproc/sunxi_rproc_kunit.c


base-commit: 7649ba73f9e7e1e04d0b46213e39c79ae09dd55c
-- 
2.53.0