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    SubjectRe: [PATCH v2 5/6] watchdog: at91sam9: request the irq with IRQF_NO_SUSPEND
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    On Thu, Mar 5, 2015 at 11:57 AM, Mark Rutland <mark.rutland@arm.com> wrote:
    > [...]
    >
    >> > > err = request_irq(wdt->irq, wdt_interrupt,
    >> > > - IRQF_SHARED | IRQF_IRQPOLL,
    >> > > + IRQF_SHARED | IRQF_IRQPOLL |
    >> > > + IRQF_NO_SUSPEND,
    >> >
    >> > I'm a little confused by this. What happens if the watchdog fires when
    >> > we're actually in the suspended state (when IRQF_NO_SUSPEND interrupts
    >> > aren't guaranteed to be delivered).
    >>
    >> Why wouldn't they be delivered?
    >>
    >> If that's suspend-to-idle, we'll handle them normally. If that's full suspend,
    >> they may not be handled at the last stage (when we run on one CPU with interrupts
    >> off), but that was the case before the wakeup interrupts rework already and I'd
    >> expect it to be taken into account somehow in the existing code (or if it isn't
    >> taken into account, we have a bug, but it is not related to this series).
    >
    > There's no enable_irq_wake(wdt->irq), and I was under the impression this
    > is for full suspend.

    enable_irq_wake() has no effect on IRQF_NO_SUSPEND interrupts, so if the
    driver uses IRQF_NO_SUSPEND, it does not need to use enable_irq_wake()
    in addition to that.

    Drivers using IRQF_COND_SUSPEND generally should use enable_irq_wake() too
    in case they end up in a situation without sharing a NO_SUSPEND interrupt, in
    which case their interrupt handlers won't be called after suspend_device_irqs(),
    so they need to rely on the core to do the wakeup.

    > I agree that if problematic, it's an existing bug. Given Boris's
    > comments in the other thread this may just a minor semantic issue w.r.t.
    > IRQF_NO_SUSPEND vs IRQF_COND_SUSPEND.

    It depends on whether or not the watchdog's interrupt handler has to be
    called immediately after receiving an interrupt (IRQF_NO_SUSPEND is
    better then) or it can be deferred till the resume_device_irqs() time.

    Rafael


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