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wifi: wfx: fix possible device hang during init

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The WFxxx device provides an SDIO interface. In addition to the usual
in-band SDIO IRQ, the device also supports out-of-band IRQ line. OOB IRQ
requires a specific initialization described in commit f00dc1d789
("staging: wfx: poll IRQ during init"):

    When the chip starts in SDIO mode, the external IRQ (aka Out-Of-Band
    IRQ) cannot be used before to configure it. Therefore, the first
    exchanges with the chip have to be done without the OOB IRQ.

    This patch allow to poll the data until the OOB IRQ is correctly
    setup. In order to keep the code simpler, this patch also poll data
    even if OOB IRQ is not used.

Commit 57aa557f11 ("staging: wfx: introduce a way to poll IRQ")
announce some limitation about the data polling mechanism:

    This function [wfx_bh_poll_irq()] must used with care: if an IRQ
    fires while the host reads control register, the IRQ can be lost.

However, with last analysis, it seems it does not only impact the IRQ.
When this condition happen the hardware is lost and won't reply the next
commands. The only way to recover the error is to pull the reset pin and
bind the device again.

Currently wfx_bh_poll_irq() is only used during the two first exchanges
with the hardware. Therefore, it has been reported to only happen after
a few hours of bind/rebind in a loop. This explain why it has not been
reported before.

Fortunately, wfx_bh_poll_irq() is only required for OOB IRQ, which is
probably very marginal. The In-Band IRQ case also uses this function,
but only to simplify the code.

This patch limits the use of wfx_bh_poll_irq() to the OOB IRQ. The bus
driver now tells wfx_probe() whether polling is necessary. When it is
not (in-band SDIO IRQ and SPI), the IRQ is subscribed before the first
exchange with the device and wfx_bh_poll_irq() is never called. When it
is (SDIO with OOB IRQ), the behavior is unchanged: the control register
is polled until the PDS file has configured the IRQ line.

To conclude, In-Band users are now safe. Users of OOB IRQ will be still
impacted by the bug, but there is nothing we can do (and nobody
complained during the last 6 years).

Fixes: f00dc1d789 ("staging: wfx: poll IRQ during init")
Reported-by: Gerard Salvatella <gerard.salvatella@siemens.com>
Reported-by: Lukas Stockmann <lukas.stockmann@siemens.com>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Tested-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://patch.msgid.link/20260901083548.113131-2-jerome.pouiller@silabs.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Jérôme Pouiller 2026-09-01 10:33:19 +02:00 • committed by Johannes Berg
commit 102f54dc47
3 changed files with 26 additions and 15 deletions
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