linux-kernel - Re: [PATCH v2] gpio: shared: handle the reset-gpios corner case

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Message-ID: <wa5fnedqtf2prksnqmb7oin5j3e5tqx7uopypkl2qwbker3inm@ed7tag6bk2qw>
Date: Wed, 26 Nov 2025 12:39:35 +0200
From: Abel Vesa <abel.vesa@...aro.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Val Packett <val@...kett.cool>, Krzysztof Kozlowski <krzk@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Linus Walleij <linus.walleij@...aro.org>, 
	Bartosz Golaszewski <brgl@...nel.org>, 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 v2] gpio: shared: handle the reset-gpios corner case

On 25-11-25 11:19:09, 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>

Tested on top of next-20251126, with Hamoa (x1e80100) CRD.

Tested-by: Abel Vesa <abel.vesa@...aro.org>