[PATCH RFC 0/9] gpio: improve support for shared GPIOs

[Bartosz Golaszewski]

On Tue, Oct 7, 2025 at 12:09 AM Manivannan Sadhasivam <mani at kernel.org> wrote:
>
> > >
> > > Not always... For something like shared reset line, consumers request the line
> > > as GPIO and expect gpiolib to do resource manangement.
> > >
> >
> > They could use the reset API and it would implicitly create a virtual
> > device that requests the reset GPIO and controls its enable count.
> > Except that some devices also do a specific reset sequence with delays
> > etc. That would require some additional logic in reset-gpio.
> >
>
> I was referring to the PCIe PERST# line, for which the 'reset-gpios' property
> already exist in the schema. Now, you want me to model this simple GPIO as a
> fake reset controller and use it the PCIe Bridge nodes through 'resets'
> property?
>

No, not at all. It's just that a shared `reset-gpios` property is
pretty common and Krzysztof implemented the reset-gpio driver[1] to
address it. Drivers that request a reset control via the OF interface
will notice that there's no `resets` property but if there's a
`reset-gpios`, the reset core will create a virtual device binding to
the reset-gpio driver which requests the GPIO in question (once!) and
registers with the reset subsystem providing shared reset control to
users. Basically the abstraction Srini mentioned minus any reset
sequence.

That only happens if the driver uses the reset API. If you go with the
GPIOLIB then none of this matters. I definitely don't want to change
the existing DT sources either but I want to find out if the code in
this series is suitable (with some modifications) for supporting the
PERST# line or if the logic behind it is more complex and possibly
requires separate, more fine-grained handling.

Bartosz

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/reset/reset-gpio.c