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SubjectRe: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs
From
On Tue, May 5, 2009 at 4:27 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Wednesday 06 May 2009, Kevin Hilman wrote:
>> Arve Hjønnevåg <arve@android.com> writes:
>>
>> > On Tue, May 5, 2009 at 8:52 AM, Kevin Hilman
>> > <khilman@deeprootsystems.com> wrote:
>> >> Andrew Morton <akpm@linux-foundation.org> writes:
>> >>
>> >>> On Mon,  4 May 2009 17:27:04 -0700 Kevin Hilman <khilman@deeprootsystems.com> wrote:
>> >>>
>> >>>> Interrupts that are flagged as wakeup sources via set_irq_wake()
>> >>>> should not be disabled for suspend.
>> >>>>
>> >>>
>> >>> Why not?
>> >>>
>> >>
>> >> If an interrupt is a wakeup source, and it is disabled at the chip
>> >> level, it will no longer generate interrupts, and thus no longer wake
>> >> up the system.
>> >>
>> >> I'd be interested in hearing why wakeup interrupts should be disabled
>> >> during suspend.
>
> That depends on whether or not they are used for anything else than wake-up.
>
>>
>> [...]
>>
>> >>>
>> >>> If this fixes some bug then please provide a description of that bug?
>> >>
>> >> The bug is that on TI OMAP, interrupts that are used for wakeup events
>> >> are disabled by this code causing the system to no longer wake up.
>> >
>> > What do you do if the interrupt triggers right after your driver has
>> > returned from its late suspend hook?
>>
>> If it's a wakeup IRQ, I assume you want it to prevent suspend.
>>
>> But I don't see how that can happen in the current code. IIUC, by the
>> time your late suspend hook is run, your device IRQ is already
>> disabled, so it won't trigger an interrupt that will be caught by
>> check_wakeup_irqs() anyways.
>
> My understanding of __disable_irq() was that it didn't actually disable the
> IRQ at the hardware level, allowing the CPU to actually receive the interrupt
> and acknowledge it, but preventing the device driver for receiving it.  Does
> it work differently on the affected systems?

If the irq_chip implements mask and unmask, then this is how it works,
but it can override this by also implementing disable. If the irq_chip
disable hook turns off the edge detection for an edge triggered wakeup
interrupt, it will not allow drivers or the framework to use
disable_irq to mask an interrupt.

--
Arve Hjønnevåg
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