On 25/01/2024 09:27, neil.armstrong@xxxxxxxxxx wrote: > On 24/01/2024 08:45, Krzysztof Kozlowski 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> >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> >> >> --- >> >> Depends on previous of change. >> --- >> drivers/reset/core.c | 215 +++++++++++++++++++++++++++++-- >> include/linux/reset-controller.h | 4 + >> 2 files changed, 206 insertions(+), 13 deletions(-) >> >> diff --git a/drivers/reset/core.c b/drivers/reset/core.c >> index 4d5a78d3c085..60a8a33c4419 100644 >> --- a/drivers/reset/core.c >> +++ b/drivers/reset/core.c > > <snip> > >> + } >> + >> + ret = __reset_add_reset_gpio_lookup(id, args->np, args->args[0], >> + args->args[1]); > > What would happen with gpio controllers using #gpio-cells = <3> (or more) like allwinner,sun4i-a10-pinctrl.yaml ? > > On this example the flags are args->args[2] so this would probably fail. > > This would also fails badly with #gpio-cells = <1>, args->args[1] value would be undefined. > > You should probably limit to args->args_count == 2 for now. Hm, good point. Both cells are actually possible, so I need to check it. Thanks. Best regards, Krzysztof
