Re: [Linux-kernel-mentees] Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model?

From: Coiby Xu <coiby.xu@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Linus Walleij <linus.walleij@linaro.org>,
	wang jun <availa@outlook.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Nehal Shah <Nehal-bakulchandra.Shah@amd.com>
Subject: Re: [Linux-kernel-mentees] Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model?
Date: Fri, 30 Oct 2020 12:54:21 +0800	[thread overview]
Message-ID: <20201030045421.si3r5zsbeeyhkwns@Rk> (raw)
In-Reply-To: <CAHp75VcEr0AcdM2+ig5neMQn+5cfuttpFuAak7CkSO-qVjPeCw@mail.gmail.com>

On Tue, Oct 27, 2020 at 06:09:49PM +0200, Andy Shevchenko wrote:
>On Tue, Oct 27, 2020 at 6:01 PM Hans de Goede <hdegoede@redhat.com> wrote:
>> On 10/27/20 4:13 PM, Andy Shevchenko wrote:
>> > On Tue, Oct 27, 2020 at 4:31 PM Hans de Goede <hdegoede@redhat.com> wrote:
>> >> On 10/26/20 11:54 PM, Coiby Xu wrote:
>> >>> Hi Hans and Linus,
>> >>>
>> >>> Will you interpret the 0x0000 value for debounce timeout in GPIO
>> >>> Interrupt Connection Resource Descriptor as disabling debouncing
>> >>> filter?
>> >>>
>> >>> GpioInt (EdgeLevel, ActiveLevel, Shared, PinConfig, DebounceTimeout, ResourceSource,
>> >>> ResourceSourceIndex, ResourceUsage, DescriptorName, VendorData) {PinList}
>> >>>
>> >>> I'm not sure if Windows' implementation is the de facto standard like
>> >>> i2c-hid. But if we are going to conform to the ACPI specs and we would
>> >>> regard 0x0000 debounce timeout as disabling debouncing filter, then we
>> >>> can fix this touchpad issue and potentially some related issues by
>> >>> implementing the feature of supporting configuring debounce timeout in
>> >>> drivers/gpio/gpiolib-acpi.c and removing all debounce filter
>> >>> configuration in amd_gpio_irq_set_type of drivers/pinctrl/pinctrl-amd.c.
>> >>> What do you think?
>> >>>
>> >>> A favorable evidence is I've collected five DSDT tables when
>> >>> investigating this issue. All 5 DSDT tables have an GpioInt specifying
>> >>> an non-zero debounce timeout value for the edge type irq and for all
>> >>> the level type irq, the debounce timeout is set to 0x0000.
>> >>
>> >> That is a very interesting observation and this matches with my
>> >> instincts which say that we should just disable the debounce filter
>> >> for level triggered interrupts in pinctrl-amd.c
>> >>
>> >> Yes that is a bit of a shortcut vs reading the valie from the ACPI
>> >> table, but I'm not sure that 0 always means disabled.
>> >>
>> >> Specifically the ACPI 6.2 spec also has a notion of pinconf settings
>> >> and the docs on "PinConfig()"  say:
>> >>
>> >> Note: There is some overlap between the properties set by GpioIo/GpioInt/ PinFunction and
>> >> PinConfig descriptors. For example, both are setting properties such as pull-ups. If the same
>> >> property is specified by multiple descriptors for the same pins, the order in which these properties
>> >> are applied is undetermined. To avoid any conflicts, GpioInt/GpioIo/PinFunction should provide a
>> >> default value for these properties when PinConfig is used. If PinConfig is used to set pin bias,
>> >> PullDefault should be used for GpioIo/GpioInt/ PinFunction. *If PinConfig is used to set debounce
>> >> timeout, 0 should be used for GpioIo/GpioInt.*
>> >>
>> >> So that suggests that a value of 0 does not necessarily mean "disabled" but
>> >> it means use a default, or possibly get the value from somewhere else such
>> >> as from a ACPI PinConfig description (if present).
>> >
>> > Nope, it was added to get rid of disambiguation when both Gpio*() and
>> > PinConfig() are given.
>> > So, 0 means default *if and only if* PinConfig() is present.
>> >
>> > I.o.w. the OS layers should do this:
>> >
>> >  - if Gpio*() provides Debounce != 0, we use it, otherwise
>> >  - if PinConfig() is present for this pin with a debounce set, use it, otherwise
>> >  - debounce is disabled.
>> >
>> > Now we missed a midentry implementation in the Linux kernel, hence go
>> > to last, i.e. disable debounce.
>> > But it should be rather done in gpiolib-acpi.c.
>> >
>> > Hope this helps.
>> >
>> > I Cc'ed this to Mika as co-author of that part of specification, he
>> > may correct me if I'm wrong.
>>
>> I see, so then the right thing to do for the bug which we are seeing
>> on some AMD platforms would be to honor the debounce setting I guess ?
>>
>> Can you and/or Mika write a patch(set) for this ?
>
>I will look at it, but meanwhile I would postpone until having a
>Mika's Ack on the action that my understanding and course of actions
>is correct.
>
If you don't mind, let me write this patch(set) instead:) I feel itchy
to fix this touchpad issue by myself after spending about a month of
my internship at Linux Foundation investigating this touchpad issue.
There are many enthusiastic Linux users waiting to get their touchpads
fixed and I could prioritize this task since I don't have other
obligations. I have provided a fallback solution [1] to save their
touchpads but it seems patches on gpiolib-acpi.c and pinctrl-amd could
reach mainline kernel much earlier.

[1] https://lore.kernel.org/patchwork/patch/1323245/
>> > P.S. Does RedHat have a representative in ASWG?
>>
>> I think so yes, but mainly focussed on server related things I guess...
>
>
>--
>With Best Regards,
>Andy Shevchenko

--
Best regards,
Coiby
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