linux-kernel - Re: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs

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Message-ID: <4d34a0a70905051720y5f9021ack3e71a7a4002a9e97@mail.gmail.com>
Date:	Wed, 6 May 2009 09:20:00 +0900
From:	Kim Kyuwon <chammoru@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Kevin Hilman <khilman@...prootsystems.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs

On Wed, May 6, 2009 at 8:27 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Wednesday 06 May 2009, Kevin Hilman wrote:
>> Arve Hjønnevåg <arve@...roid.com> writes:
>>
>> > On Tue, May 5, 2009 at 8:52 AM, Kevin Hilman
>> > <khilman@...prootsystems.com> wrote:
>> >> Andrew Morton <akpm@...ux-foundation.org> writes:
>> >>
>> >>> On Mon,  4 May 2009 17:27:04 -0700 Kevin Hilman <khilman@...prootsystems.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?

Hi Rafael,

You can refer to:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5461af5af5c6a7fee78978aafe720541bf3a2f55

Thanks,
Kyuwon
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