Re: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs
From: Rafael J. Wysocki
Date: Fri May 29 2009 - 19:35:32 EST
On Monday 25 May 2009, Kim Kyuwon wrote:
> Rafael J. Wysocki wrote:
> > On Saturday 23 May 2009, Kim Kyuwon wrote:
> >> On Sat, May 23, 2009 at 7:29 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> >>> On Saturday 23 May 2009, Kim Kyuwon wrote:
> > [--snip--]
> >>>> You changed the really important part of Linux, which may affect most
> >>>> processor architectures. I think you should be careful. If some of
> >>>> architectures can't take care of it (they can implement
> >>>> disable_irq_wake correctly in H/W level, will you revert your changes?
> >>> No, the changes are not going to be reverted. In fact things should have been
> >>> done like this already much earlier.
> >>> Now, do you have any particular example of a problem related to these changes
> >>> or is it only a theoretical issue?
> >> I'd CCing you when I'm sending a mail for this particular example of a example.
> >> http://markmail.org/thread/fvt7d62arofon5xx
> > Well, as I said above, reverting the changes that introduced
> > [suspend|resume]_device_irqs() is not an option, becuase it was the only sane
> > way to achieve the goal they were added for. So, we need to fix the wake-up
> > problem on your platform with the assumption that
> > [suspend|resume]_device_irqs() are going to stay.
> > For starters, would it be possible to teach the 'disable' hook of your
> > platform's interrupt controller not to mask the IRQs that have both
> > IRQ_WAKEUP and IRQ_SUSPENDED set? That apparently would work around the
> > wake-up interrupts problem.
> Thank you for considering this issue and spending your time. In order to
> make your idea work, we need to add a dummy 'set_wake' hook which
> returns always zero. Anyway, IMO, I think your idea is good to work
> around this problem. But Kevin Hilman(OMAP PM Maintainer) would make
> final decision.
> Buy the way, how can you handle the problem that a few interrupt are
> discarded in a small window? I can be sure they are discarded, because I
> have debugged defects which generate in sleep/resume state hundreds of
> times on ARM Processors(PXA310, S3C6410, OMAP3430). Wake-up interrupts
> are generated as soon as arch_suspend_enable_irqs() invoked.
Sorry for the delayed response.
If the wake-up interrupts are not masked, they will be delivered to the drivers
as soon as arch_suspend_enable_irqs() has run. So, if the drivers are able to
handle them at this point (ie. before resume_device_irqs() is called), they
won't be lost. The only problem I see is that the drivers may expect their
->resume_noirq() callbacks to be executed first.
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