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 03:34:55PM +0000, Limonciello, Mario wrote:
> On 6/25/25 10:17 AM, Andy Shevchenko wrote:
> > On Wed, Jun 25, 2025 at 03:14:40PM +0000, Limonciello, Mario wrote:
> >> On 6/25/25 10:10 AM, Andy Shevchenko wrote:
> >>> 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).
> >>
> >> But 0 doesn't mean hardware debounce support is there, 0 means that
> >> hardware debounce is not required to be programmed for this GPIO.
> >>
> >> That is - if another system had a non-zero value in the GpioInt entry I
> >> would expect this to be translated into the GPIO register.
> > 
> > Correct. The question is only about 0. So the flow will look like
> > 
> > 1) if the GPIO is defined with 0 debounce, set the flag;
> > 2) if the GPIO is defined with non-zero value, try to apply it;
> > 3) if the step 2) fails, warn and set the flag.
> > 
> > Would it make sense?
> > Hans?
> 
> But so on these problematic BYT/CYT tablets which "layer" should be 
> setting the 50ms debounce?
> That should still be a quirk at the soc_button_array layer, right?
> 
> Because gpio_keys_setup_key() will already fallback to software 
> debounce, and the goal here is that both of those only use the 50ms 
> specifically with software debouncing.

Probably gpiod_set_debounce() should become a no-op in this case?

-- 
With Best Regards,
Andy Shevchenko