Re: [PATCH v2 0/2] gpio: fix sleeping-in-atomic in shared-proxy; restore meson non-sleeping

[Bartosz Golaszewski <brgl@kernel.org>]

On Thu, 25 Jun 2026 13:57:16 +0200, Viacheslav Bocharov <v@baodeep.com> said:
> gpio-shared-proxy chooses its descriptor lock (mutex vs spinlock) from
> the underlying chip's can_sleep, but under that lock it calls config and
> direction ops that reach sleeping pinctrl paths. On a controller with
> non-sleeping MMIO value ops the lock is a spinlock, so a sleeping call
> runs from atomic context:
>
>   BUG: sleeping function called from invalid context
>     ... pinctrl_gpio_set_config <- gpiochip_generic_config
>     <- gpio_shared_proxy_set_config (voting spinlock held)
>     <- ... <- mmc_pwrseq_simple_probe
>
> This was reported on Khadas VIM3 and worked around for Amlogic by
> commit 28f240683871 ("pinctrl: meson: mark the GPIO controller as
> sleeping"), which marked the whole meson controller sleeping. That
> workaround broke atomic value-path consumers: w1-gpio (1-Wire bitbang)
> no longer detects devices, because its IRQ-disabled read slot calls the
> non-cansleep gpiod_*_value() and now hits WARN_ON(can_sleep) per bit.
>
> Patch 1 fixes the proxy locking generically (always a sleeping mutex).
> Patch 2 then restores meson can_sleep=false, fixing 1-Wire.
>
> Patch 1 has a trade-off: a proxied GPIO becomes sleeping, so consumers
> gating on gpiod_cansleep() change behaviour. No current device needs
> atomic (non-cansleep) value access on a shared GPIO -- every report
> (Khadas VIM3, ODROID-M1, my test on JetHub D1+) is a shared reset line
> (eMMC/SDIO pwrseq or PCIe reset) driven through the cansleep accessors,
> which is what the proxy exists to vote on; bit-banging that needs atomic
> access cannot work through voting anyway. An alternative that keeps
> atomic value access (split locking) is possible but adds a second lock
> and new race windows, so this series takes the simpler mutex-only
> approach.
>
> The two are a unit: patch 2 must not be applied without patch 1,
> otherwise the original VIM3 splat returns on boards that share a meson
> GPIO -- please keep the order. I have not Cc'd stable; I will request
> stable backports separately once both patches have landed.
>
> Changes since v1:
> - gpio: shared-proxy: open-code the descriptor mutex; drop the
>   gpio_shared_desc_lock guard and the gpio_shared_lockdep_assert()
>   helper, move the mutex rationale to the can_sleep assignment. No
>   functional change.
>
> v1: https://lore.kernel.org/linux-gpio/20260610153329.937833-1-v@baodeep.com/
>
> Viacheslav Bocharov (2):
>   gpio: shared-proxy: always serialize with a sleeping mutex
>   pinctrl: meson: restore non-sleeping GPIO access
>
>  drivers/gpio/gpio-shared-proxy.c      | 66 +++++++++++----------------
>  drivers/gpio/gpiolib-shared.c         |  9 +---
>  drivers/gpio/gpiolib-shared.h         | 28 +-----------
>  drivers/pinctrl/meson/pinctrl-meson.c |  2 +-
>  4 files changed, 30 insertions(+), 75 deletions(-)
>
>
> base-commit: 840ef6c78e6a2f694b578ecb9063241c992aaa9e
> --
> 2.54.0
>
>

I have no idea what's wrong but I'm still getting two copies of each email
as separate messages to my inbox. I'm not seeing it with anyone else. I think
there's some issue with your setup.

Bart

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