On Mon, Feb 12, 2024 at 9:48 PM Linus Walleij linus.walleij@linaro.org wrote:
On Mon, Jan 29, 2024 at 12:53 PM Krzysztof Kozlowski krzysztof.kozlowski@linaro.org wrote:
Devices sharing a reset GPIO could use the reset framework for coordinated handling of that shared GPIO line. We have several cases of such needs, at least for Devicetree-based platforms.
If Devicetree-based device requests a reset line, while "resets" Devicetree property is missing but there is a "reset-gpios" one, instantiate a new "reset-gpio" platform device which will handle such reset line. This allows seamless handling of such shared reset-gpios without need of changing Devicetree binding [1].
To avoid creating multiple "reset-gpio" platform devices, store the Devicetree "reset-gpios" GPIO specifiers used for new devices on a linked list. Later such Devicetree GPIO specifier (phandle to GPIO controller, GPIO number and GPIO flags) is used to check if reset controller for given GPIO was already registered.
If two devices have conflicting "reset-gpios" property, e.g. with different ACTIVE_xxx flags, this would allow to spawn two separate "reset-gpio" devices, where the second would fail probing on busy GPIO request.
Link: https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@robh.at.kernel.org/ [1] Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: Chris Packham chris.packham@alliedtelesis.co.nz Cc: Sean Anderson sean.anderson@seco.com Reviewed-by: Philipp Zabel p.zabel@pengutronix.de Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org
Acked-by: Linus Walleij linus.walleij@linaro.org
I can't think of anything better, that is reasonable to ask for.
I feel slightly icky about the way the code reaches into gpiolib, and I think
As long as it doesn't include gpiolib.h, I'm fine with it.
regulators should be able to reuse the code, but unfortunately only the day they have no board files left :/
I do feel the core code handling "reset-gpios" could as well have been used to handle "enable-gpios" in regulators, just that the regulator code has more requirements, and would be really hard to rewrite, and deals with descriptors passed in from drivers instead of centralizing it.
Like regulators, reset grows core support for handling GPIO for resets which is *long due*, given how common it must be. We really need something like this, and this is certainly elegant enough to do the job.
Yours, Linus Walleij
Agreed.
Acked-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org
I will pick up the stub patches tomorrow and send a tag for Philipp to pull.
Bartosz