linux-kernel - Re: [PATCH 2/2] Revert "Input: soc_button_array

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Message-ID: <aFwTCUXQydxRVEfk@smile.fi.intel.com>
Date: Wed, 25 Jun 2025 18:17:29 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: "Limonciello, Mario" <Mario.Limonciello@....com>
Cc: Mario Limonciello <superm1@...nel.org>,
	Hans de Goede <hansg@...nel.org>,
	Mika Westerberg <westeri@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"open list:GPIO ACPI SUPPORT" <linux-gpio@...r.kernel.org>,
	"open list:GPIO ACPI SUPPORT" <linux-acpi@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:INPUT (KEYBOARD, MOUSE, JOYSTICK, TOUCHSCREEN)..." <linux-input@...r.kernel.org>
Subject: Re: [PATCH 2/2] Revert "Input: soc_button_array - debounce the
 buttons"

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?

-- 
With Best Regards,
Andy Shevchenko