On 18/07/2015 at 10:20:53 +0200, Thomas Gleixner wrote :
> On Fri, 17 Jul 2015, Alexandre Belloni wrote:
> > /*
> > + * IRQ handler for the timer.
> > + */
> > +static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
> > +{
> > + struct pit_data *data = dev_id;
> > +
> > + /*
> > + * irqs should be disabled here, but as the irq is shared they are only
> > + * guaranteed to be off if the timer irq is registered first.
>
> That's wrong. We run all handlers with interrupts disabled for about 5
> years now.
>
> > + */
> > + WARN_ON_ONCE(!irqs_disabled());
>
Yeah, I was skeptical when I read that...
>
> > + /* The PIT interrupt may be disabled, and is shared */
> > + if (clockevent_state_periodic(&data->clkevt) &&
> > + (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
> > + unsigned nr_ticks;
> > +
> > + /* Get number of ticks performed before irq, and ack it */
> > + nr_ticks = PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
> > + do {
> > + data->cnt += data->cycle;
> > + data->clkevt.event_handler(&data->clkevt);
> > + nr_ticks--;
> > + } while (nr_ticks);
>
> I don't think you need this loop. You have a proper clocksource
> registered so the timekeeping code will handle the lost ticks nicely.
>
... for both comments, this is just code I'm moving from one place to
another. I'll have a look a clean that up in a preliminary patch.
Thanks!
--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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