Re: [PATCH 2/2] Revert "Input: soc_button_array - debounce the buttons"

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Wed, Jun 25, 2025 at 03:02:18PM +0000, Limonciello, Mario wrote:
> On 6/25/25 9:41 AM, Mario Limonciello wrote:
> > On 6/25/25 9:31 AM, Hans de Goede wrote:
> >> On 25-Jun-25 4:09 PM, Mario Limonciello wrote:
> >>> On 6/25/25 4:09 AM, Hans de Goede wrote:
> >>>> On 24-Jun-25 10:22 PM, Mario Limonciello wrote:

...

> >> Ok, so specifically the gpiod_set_debounce() call with 50 ms
> >> done by gpio_keys.c is the problem I guess?
> > 
> > Yep.
> > 
> >> So amd_gpio_set_debounce() does accept the 50 ms debounce
> >> passed to it by gpio_keys.c as a valid value and then setting
> >> that breaks the wake from suspend?
> > 
> > That's right.

> >>> Also comparing the GPIO register in Windows (where things work) 
> >>> Windows never programs a debounce.
> >>
> >> So maybe the windows ACPI0011 driver always uses a software-
> >> debounce for the buttons? Windows not debouncing the mechanical
> >> switches at all seems unlikely.
> >>
> >> I think the best way to fix this might be to add a no-hw-debounce
> >> flag to the data passed from soc_button_array.c to gpio_keys.c
> >> and have gpio_keys.c not call gpiod_set_debounce()  when the
> >> no-hw-debounce flag is set.
> >>
> >> I've checked and both on Bay Trail and Cherry Trail devices
> >> where soc_button_array is used a lot hw-debouncing is already
> >> unused. pinctrl-baytrail.c does not accept 50 ms as a valid
> >> value and pinctrl-cherryview.c does not support hw debounce
> >> at all.
> > 
> > That sounds a like a generally good direction to me.

Thinking a bit more of this, perhaps the HW debounce support flag should be
per-GPIO-descriptor thingy. In such cases we don't need to distinguish the
platforms, the GPIO ACPI lib may simply set that flag based on 0 read from
the ACPI tables. It will also give a clue to any driver that uses GPIOs
(not only gpio-keys).

-- 
With Best Regards,
Andy Shevchenko