On Mon, Feb 12, 2024 at 9:48 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > On Mon, Jan 29, 2024 at 12:53 PM Krzysztof Kozlowski > <krzysztof.kozlowski@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx/ [1] > > Cc: Bartosz Golaszewski <brgl@xxxxxxxx> > > Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> > > Cc: Sean Anderson <sean.anderson@xxxxxxxx> > > Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > > Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > > 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@xxxxxxxxxx> I will pick up the stub patches tomorrow and send a tag for Philipp to pull. Bartosz
