[PATCH wireless 0/2] wifi: iwlwifi: recover the device after it loses power in D3cold

[Navon John Lukose <navonjohnlukose@gmail.com>]

On several Meteor Lake laptops the Intel BE200 does not survive a D3cold
transition: the platform's _PR3 power resource genuinely removes the M.2
module's rail, and the card does not restart when the rail and PERST# are
restored. Config space reads 0xffffffff, the link never trains, and the
device stays gone until a reboot.

iwlwifi already has everything needed to recover it. The platform-level
device reset walks _PRR and evaluates _RST, and the vendor _DSM that arms
it is already spoken. The problem is ordering: arming happens from the
removal path, by which point the device no longer answers, and the _DSM is
gated on the firmware reading the device's PCI ID back out of config
space. So arming can never succeed at the one moment it matters.

Patch 1 arms it at probe, while the device still answers. Patch 2 asks for
a product reset when the device is not on the bus after resume, instead of
re-initialising hardware that is not there.

Analysis, register dumps and the discussion this came out of:
Link: https://lore.kernel.org/all/20260829093922.37103-1-navonjohnlukose@gmail.com/

Tested on a Lenovo Yoga Pro 7 14IAH10 (BIOS QGCN35WW), BE200
SUBSYS_00F48086: the card dies in D3cold on every s2idle exactly as
before, and recovers on its own in about 5s, repeatedly, with wifi both
connected and idle at suspend time. With the reset skipped but everything
else identical it stays absent, so the reset is what recovers it rather
than the remove/rescan.

Caveats: one machine and one BIOS, discrete (!integrated) path only - I
have no CNVi hardware, so the integrated arming mask is untested.
Recovery costs ~4.3s of Sleep() inside the platform's _RST, which is
firmware and not something we can shorten.

Tagged for stable: the PLDR path has never worked on platforms with this
_DSM gate, and both changes are small and self-limiting - every _RST
evaluation is already preceded by set_product_reset() setting the mode
that reset wants, so arming at probe cannot alter the behaviour of any
later reset.

Signed-off-by: Navon John Lukose <navonjohnlukose@gmail.com>

Navon John Lukose (2):
  wifi: iwlwifi: pcie: arm the product reset at probe
  wifi: iwlwifi: pcie: request a product reset when the device is gone
    after resume

 drivers/net/wireless/intel/iwlwifi/pcie/drv.c          | 12 ++++++++++++
 drivers/net/wireless/intel/iwlwifi/pcie/gen1_2/trans.c |  5 +++++
 2 files changed, 17 insertions(+)