Re: [PATCH 2/3] pinctrl:Intel: clear interrupt status for every IRQ setup

["Westerberg, Mika" <mika.westerberg@xxxxxxxxx>]

On Mon, Mar 14, 2016 at 01:40:39PM +0100, Linus Walleij wrote:
> On Mon, Mar 14, 2016 at 9:44 AM, Westerberg, Mika
> <mika.westerberg@xxxxxxxxx> wrote:
> > On Mon, Mar 14, 2016 at 03:24:06AM +0200, Zheng, Qi wrote:
> 
> >> > +   intel_gpio_irq_ack(d);
> >>
> >> > If the pin toggles right here, we still have the same issue, no?
> >>
> >> Yes. But it is very short time from here to the place IRQ got enabled.
> >
> > That is still a race.
> >
> >> To me, it is the only available platform dependent interface to do
> > the "ACK" in the flow of request_irq. Maybe you have other better
> > option here?
> (...)
> > Drivers need to deal with the fact that they might get spurious
> > interrupts from time to time. You need to check in the interrupt handler
> > if the interrupt was from the device you are driving or not.
> >
> > request_irq() enables the interrupt line and if the pin is already in
> > a state that triggers an interrupt, the driver interrupt handler will
> > be called.
> 
> This looks like something is wrong in the irqchip.

If request_irq() is called so that the interrupt is level triggered,
let's say active low, and the pin is already in that state I would
expect interrupt to trigger immediately when enabled, no?

If I understand correctly this is precisely what Zheng is describing
they are trying to solve.

> Your set_type() is supporting edges but have all IRQs
> handled by handle_simple_irq() rather than handle_edge_irq()
> for the edges, which gives a more robust control flow
> from IRQ to ACK to calling the handler.
> 
> Zheng/Mika: please look at how the level/edge
> IRQs are handled in drivers/gpio/gpio-pl061.c
> where I *tried* to do things right, switching handler
> in .set_type() using irq_set_handler_locked(). I think
> you may need to use handle_edge_irq() for the edge IRQs
> and handle_level_irq() for the level IRQs just like I do
> in the PL061 driver.

The driver is already doing that as far as I can tell (see
intel_gpio_irq_type()).
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