linux-kernel - Re: [PATCH] gpio: shared: handle the reset-gpios corner case

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Message-ID: <be7fd390-e81d-4e93-880a-1b6404398408@packett.cool>
Date: Sat, 22 Nov 2025 22:03:19 -0300
From: Val Packett <val@...kett.cool>
To: Bartosz Golaszewski <brgl@...ev.pl>, Krzysztof Kozlowski
 <krzk@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 Linus Walleij <linus.walleij@...aro.org>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-msm@...r.kernel.org,
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH] gpio: shared: handle the reset-gpios corner case


On 11/21/25 10:46 AM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> There's an unexpected interaction between the reset-gpio driver and the
> shared GPIO support. The reset-gpio device is an auxiliary device that's
> created dynamically and fulfills a similar role to the gpio-shared-proxy
> driver but is limited in scope to just supporting the "reset-gpios"
> property.
>
> The shared GPIO core code does not take into account that the machine
> lookup entry we create when scanning the device-tree must connect the
> reset-gpio device - that is the actual consumer of the GPIO and not the
> consumer defined on the device tree, which in turn consumes the shared
> reset control exposed by the reset-gpio device - to the GPIO controller.
>
> We also must not skip the gpio-shared-proxy driver as it's possible that
> a shared GPIO may be used by one consumer as a reset-gpios going through
> the reset-gpio device and another that uses GPIOLIB.
>
> We need to make it a special case handled in gpiolib-shared.c. Add a new
> function - gpio_shared_dev_is_reset_gpio() - whose role it is to verify
> if a non-matching consumer of a shared pin is a reset-gpio device and
> make sure it's the right one for this pin. To that end make sure that
> its parent is the GPIO controller in question and that the fwnode we
> identified as sharing the pin references that controller via the
> "reset-gpios" property.
>
> Only include that code if the reset-gpio driver is enabled.
>
> Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
> Reported-by: Val Packett <val@...kett.cool>
> Closes: https://lore.kernel.org/all/3b5d9df5-934d-4591-8827-6c9573a6f7ba@packett.cool/
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
> This is targetting linux-next where the reset-gpio driver is now using
> the auxiliary bus and software nodes rather than the platform bus and
> GPIO machine lookup. The bug is the same in both cases but the fix would
> be completely different.
> ---
> [..]

Tried applying only this, as well as this + 
https://lore.kernel.org/all/20251120-reset-gpios-swnodes-v7-0-a100493a0f4b@linaro.org/ 
+ https://lore.kernel.org/all/20251121135739.66528-1-brgl@bgdev.pl/ (on 
top of next-20251120) and the issue is still present.. am I missing 
something?

~val