On Sat, Oct 03, 2020 at 03:22:46PM +0200, Hans de Goede wrote:

Hi,

On 10/3/20 12:45 AM, Coiby Xu wrote:

quoted

On Fri, Oct 02, 2020 at 09:44:54PM +0200, Hans de Goede wrote:

quoted

Hi,

On 10/2/20 4:51 PM, Coiby Xu wrote:

quoted

On Fri, Oct 02, 2020 at 03:36:29PM +0200, Hans de Goede wrote:

<snip>

quoted

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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 alonet
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.

I'm not sure if it's correct to say if hi2c-hid irq fires or not and how
frequently it fires since the i2c-hid irq is mapped to pin#130 of the
GPIO interrupt controller and the touchpad has another interrupt line
connected to pin#130 which fires to indicate new data. All we know is
pin#130 of the GPIO chip has low input most of the time when the finger
is on the touchpad so we can infer the touchpad has been trying to
notify the kernel of new data but somehow GPIO's parent irq only fires 7
times / second.

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.

I also doubted if it takes too much time for the i2c-hid handler to
finish reading i2c transfer, processing data and delivering to the input
system. After measuring the time internal between the starting of the
GPIO irq's parent handler and when pin#130 is unmasked, we can exclude
this possibility.

I have been wondering if we let make pin#130 have low input thus to
trigger a interrupt firing or assert the GPIO's common interrupt output
line manually thus we can measure how long does it take for the kernel
to receive the signal. But once GPIO's pin is programmed to be a
interrupt line we can't write anything to it and it seems other
interrupts can only be generated by the hardware. So this idea is not
plausible

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

Thank you for taking time to investigate this issue anyway! Have a nice
weekend:)

Regards,

Hans

--
Best regards,
Coiby
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