Re: [PATCH 1/1] pinctrl: ocelot: fix system hang on level based interrupts

[Linus Walleij]

On Fri, Oct 11, 2024 at 5:40 PM Sergey Matsievskiy
<matsievskiysv@xxxxxxxxx> wrote:
> On Fri, Oct 11, 2024 at 11:18:55AM +0200, Linus Walleij wrote:

> > I'm a bit puzzled by the patch because I don't understand it.
>
> The current implementation only calls chained_irq_enter() and chained_irq_exit()
> if it detects pending interrupts.
>
> ```
> for (i = 0; i < info->stride; i++) {
>         uregmap_read(info->map, id_reg + 4 * i, &reg);
>         if (!reg)
>                 continue;
>
>         chained_irq_enter(parent_chip, desc);
> ```
>
> However, in case of GPIO pin configured in level mode and the parent controller
> configured in edge mode, GPIO interrupt might be lowered by the hardware. In the
> result,if the interrupt is short enough, the parent interrupt is still pending
> while the GPIO interrupt is cleared; chained_irq_enter() never gets called and
> the system hangs trying to service the parent interrupt.
>
> Moving chained_irq_enter() and chained_irq_exit() outside the for loop ensures
> that they are called even when GPIO interrupt is lowered by the hardware.
>
> The similar code with chained_irq_enter() / chained_irq_exit() functions
> wrapping interrupt checking loop may be found in many other drivers:
> ```
> grep -r -A 10 chained_irq_enter drivers/pinctrl
> ```
>
> > This needs to describe how moving the chained irq calls achieves
> > this effect.
>
> If the explanation above satisfies you, I'll elaborate the commit message and
> resend the patch.

Excellent explanation Sergey, just put it all in the committ message
and I'll apply it!

Yours,
Linus Walleij