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SubjectRe: + rtc-disable-hpet-emulation-on-suspend.patch added to -mm tree

* Maxim Levitsky <maximlevitsky@gmail.com> wrote:

> On Wed, 2009-10-14 at 07:56 +0200, Ingo Molnar wrote:
> > * akpm@linux-foundation.org <akpm@linux-foundation.org> wrote:
> >
> > > ------------------------------------------------------
> > > Subject: rtc: disable hpet emulation on suspend
> > > From: Maxim Levitsky <maximlevitsky@gmail.com>
> > >
> > > I noticed that rtc wont generate interrupts after a resume from disk.
> > > Here hpet rtc emulation is used.
> > >
> > > Problem is that rtc hpet comparator, isn't reinitialized after resume.
> > > Easiest way to solve this, is always mask all hpet interrupts on suspend
> > > This is triggered, when suspending with alarm set.
> > >
> > >
> > > Otherwise, hpet driver will think it doesn't need to reinitialize
> > > the rtc comparator, thus rtc interrupts won't work.
> > >
> > > This emulation isn't need for wakealarm.
> >
> > > - hpet_mask_rtc_irq_bit(mask);
> > >
> > > + /* shut down hpet emulation - we don't need it for alarm */
> > > + hpet_mask_rtc_irq_bit(RTC_PIE|RTC_AIE|RTC_UIE);
> > > cmos_checkintr(cmos, tmp);
> >
> > Would be nice to also unconditionally reinitialize the hpet/rtc after
> > resume - regardless of what state we left it in.
>
> I think this is already done.
> Problem was that rtc driver was leaving the RTC_AIE, thus breaking the
> initialization.
>
> If there are no users of hpet on suspend, (periodic,alarm,update), then
> it won't be initialized on resume (only rtc comparator part, other parts
> are initialized correctly nowadays) but as soon as anybody start using
> it, it will be.
>
>
> >
> > Also, are you sure this does not break things like
> > CONFIG_PM_TEST_SUSPEND=y which rely on wakealarm?
>
>
> This shouldn't break anything. hpet irqs aren't used for the actual
> alarm.
>
> In fact I used a script to loop over real hibernation cycles, and it
> works with or without this patch.
>
> But with this patch, hwclock works after a resume.

Excellent - thanks!

Ingo


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