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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 10/3/20 12:45 AM, Coiby Xu wrote:
> On Fri, Oct 02, 2020 at 09:44:54PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 10/2/20 4:51 PM, Coiby Xu wrote:
>>> On Fri, Oct 02, 2020 at 03:36:29PM +0200, Hans de Goede wrote:
>>
>> <snip>
>>
>>>>>> So are you seeing these 7 interrupts / second for the touchpad irq or for
>>>>>> the GPIO controllers parent irq ?
>>>>>>
>>>>>> Also to these 7 interrupts/sec stop happening when you do not touch the
>>>>>> touchpad ?
>>>>>>
>>>>> I see these 7 interrupts / second for the GPIO controller's parent irq.
>>>>> And they stop happening when I don't touch the touchpad.
>>>>
>>>> Only from the parent irq, or also on the touchpad irq itself ?
>>>>
>>>> If this only happens on the parent irq, then I would start looking at the
>>>> amd-pinctrl code which determines which of its "child" irqs to fire.
>>>
>>> This only happens on the parent irq. The input's pin#130 of the GIPO
>>> chip is low most of the time and pin#130.
>>
>> Right, but it is a low-level triggered IRQ, so when it is low it should
>> be executing the i2c-hid interrupt-handler. If it is not executing that
>> then it is time to look at amd-pinctrl's irq-handler and figure out why
>> that is not triggering the child irq handler for the touchpad.
>>
> I'm not sure if I have some incorrect understandings about GPIO
> interrupt controller because I don't quite follow your reasoning.
> What I actually suspect is there's something wrong with amd-pinctrl
> which makes the GPIO chip fail to assert its common interrupt output
> line connected to one IO-APIC's pin#7 thus IRQ#7 fails to fire. What
> I learn about this low-level triggered IRQ is that the i2c-hid
> interrupt-handler will be woken up by amd-pinctrl's irq-handler which
> is executed when the parent IRQ#7 fires. The code path is as follows,
> 
>      <IRQ>
>      dump_stack+0x64/0x88
>      __irq_wake_thread.cold+0x9/0x12
>      __handle_irq_event_percpu+0x80/0x1c0
>      handle_irq_event+0x58/0xb0
>      handle_level_irq+0xb7/0x1a0
>      generic_handle_irq+0x4a/0x60
>      amd_gpio_irq_handler+0x15f/0x1b0 [pinctrl_amd]
>      __handle_irq_event_percpu+0x45/0x1c0
>      handle_irq_event+0x58/0xb0
>      handle_fasteoi_irq+0xa2/0x210
>      do_IRQ+0x70/0x120
>      common_interrupt+0xf/0xf
>      </IRQ>
> 
> But the problem is somehow IRQ#7 doesn't even fire when the input's
> pin#130 of the GIPO is low. Without IRQ#7 firing, amd-pinctrl's
> irq-handler wouldn't be executed in the first place, let alone
> triggering the child irq handler. Btw, amd-pinctrl's irq-handler
> simply iterate over all pins. If there is mapped irq found for this
> hwirq (yes, it won't even check if this pin triggers the interrupt),
> then it will call generic_handle_irq. So there's nothing wrong about
> this part of code.

Ok, so the i2c-hid irq does fire, but only 7 times a second just
like the GPIO controller's parent irq.

The only thing I can think of then is to add printk-s to check how
long the i2c-hid interrupt handler takes to complete. It could be
there is a subtle bug somewhere causing the i2c transfers to take
longer when run from a (threaded) irq handler. That would be weird
though, so I don't expect this to result in any useful findings.

Other then that I'm all out of ideas I'm afraid.

Regards,

Hans

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