Re: [PATCH v2 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs

[Doug Anderson]

Hi,

On Thu, Dec 10, 2020 at 11:07 PM Maulik Shah <mkshah@xxxxxxxxxxxxxx> wrote:
>
> I have slightly modified your test case (see at
> https://crrev.com/c/2584729) which is as per what i used in my testing.
>
> Here is what i am doing, setting GPIO to a fixed function (function 2 here)
> Note that function 0 is the GPIO (interrupt mode).
>
> 1) Pull up the GPIO in function 2
> 2) Pull down the GPIO in function 2
>
> Repeat above steps, and you will see fake interrupt every time pull down/up.
> This proves that if you mux away from GPIO then still PDC sees the line
> and can latch the interrupt at GIC.

Ah, super useful example!  Thanks!  Yes, I can replicate your results.

...but this seems to contradict my other test.  Ah, dang, I think I
see the problem with my original test.  The important difference is
that in your test you used the alternate function "mi2s_2" and in mine
I used "qspi_data".  When I selected "qspi_data" it must have been
actively driving the pin and _that's_ why I couldn't affect it.

When I change my test to use "mi2s_2" then my toggles via "wp enable"
and "wp disable" cause phantom interrupts.  That confirms what you're
saying: the PDC _can_ see the twiddles even when muxed away.
Presumably the active driving my "qspi_data" is also what caused my
phantom glitches.

So, as you said, that means my mental model is totally wrong here.
Wow, if I had known that earlier I would have saved a lot of time.
That'll learn me...

OK, v4 being posted and you can see if that handles all the cases?

-Doug