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

Linus Walleij linus.walleij at linaro.org
Thu Oct 1 20:57:40 UTC 2020

Sorry for top posting, but I want to page some people.

I do not know anything about ACPI, but Hans de Goede is really
good with this kind of things and could possibly provide some

Linus Walleij

On Thu, Oct 1, 2020 at 3:23 PM Coiby Xu <coiby.xu at gmail.com> wrote:
> Hi,
> I'm trying to fix broken touchpads [1] for a new laptop model Legion-5
> 15ARH05 which is shipped with two different touchpads, i.e., ElAN and
> Synaptics. For the ELAN touchpad, the kernel receives no interrupts to
> be informed of new data from the touchpad. For the Synaptics touchpad,
> only 7 interrupts are received per second which makes the touchpad
> completely unusable. Based on current observations, pinctrl-amd seems to
> be the most suspicious cause.
> Why do I think pinctrl-amd smells the most suspicious?
> ======================================================
> This laptop model has the following hardware configurations specified
> via ACPI,
>   - The touchpad's data interrupt line is connected to pin#130 of a GPIO
>     chip
>          GpioInt (Level, ActiveLow, ExclusiveAndWake, PullUp, 0x0000,
>                          "\\_SB.GPIO", 0x00, ResourceConsumer, ,
>                          )
>                          {   // Pin list
>                              0x0082
>                          }
>   - This GPIO chip (HID: AMDI0030) which is assigned with IRQ#7 has its
>     common interrupt output line connected to one IO-APIC's pin#7
>          Interrupt (ResourceConsumer, Level, ActiveLow, Shared, ,, )
>          {
>              0x00000007,
>          }
> I add some code to kernel to poll the status of the GPIO chip's pin#130
> and IO-APIc's pin#7 every 1ms when I move my finger on the surface of
> the Synaptics touchpad continuously for about 1s. During the process of I
> move my finger, most of the time,
>   - GPIO chip's pin#130: low input, interrupt unmasked
>   - IO-APIC's pin#7: IRR=0, interrupt unmasked (in fact mask/unmask_ioapic_irq
>     have never been called by the IRQ follow controller handle_fasteoi_irq)
> So the touchpad has been generating interrupts most of the time while
> IO-APIC controller hasn't been masking the interrupt from the GPIO chip.
> But somehow the kernel could only get ~7 interrupts each second while
> the touchpad could generate 140 interrupts (time resolution of 7.2ms)
> per second. Assuming IO-APIC (arch/x86/kernel/apic/io_apic.c) is fine,
> then there's something wrong with the GPIO interrupt controller which
> works fine for the touchpad under Windows. Besides if I poll the touchpad
> data based on pin#130's status, the touchpad could also work under
> Windows.
> Ways to debug pinctrl-amd
> =========================
> I can't find any documentation about the AMDI0030 GPIO chip except for
> the commit logs of drivers/pinctrl/pinctrl-amd. One commit
> ba714a9c1dea85e0bf2899d02dfeb9c70040427c ("pinctrl/amd: Use regular interrupt instead of chained")
> inspired me to bring back chained interrupt to see if "an interrupt storm"
> would happen. The only change I noticed is that the interrupts arrive in
> pairs. The time internal between two interrupts in a pair is ~0.0016s
> but the time internal between interrupt pairs is still ~0.12s (~8Hz).
> Unfortunately, I don't get any insight about the GPIO interrupt
> controller from this tweaking. I wonder if there are any other ways
> to debug drivers/pinctrl/pinctrl-amd?
> Thank you!
> [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1887190
> --
> Best regards,
> Coiby

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