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[PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3

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  [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3 zhuo-hao.lee@intel.com - 2015-11-17 13:10 +0100
    Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system  resume from S3 John Stultz <john.stultz@linaro.org> - 2015-11-20 20:30 +0100
      RE: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system  resume from S3 "Lee, Zhuo-hao" <zhuo-hao.lee@intel.com> - 2015-11-23 03:00 +0100
      Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system  resume from S3 Thomas Gleixner <tglx@linutronix.de> - 2015-11-25 15:30 +0100
        Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system  resume from S3 John Stultz <john.stultz@linaro.org> - 2015-11-25 22:50 +0100

#1271125 — [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3

From: zhuo-hao <zhuo-hao.lee@intel.com>

Before the system go to suspend (S3), if user create a timer with clockid
CLOCK_REALTIME_ALARM/CLOCK_BOOTTIME_ALARM and set a "large" timeout value
to this timer. The function alarmtimer_suspend will be called to setup
a timeout value to RTC timer to avoid the system sleep over time. However,
if the system wakeup early than RTC timeout, the RTC timer will not be cleared.
And this will cause the hpet_rtc_interrupt come unexpectedly until the RTC
timeout. To fix this problem, just adding alarmtimer_resume to cancel the
RTC timer.

This was noticed because the HPET RTC emulation fires an interrupt every
16ms(=1/2^DEFAULT_RTC_SHIFT) up to the point where the alarm time is reached.
This program always hits this situation(https://lkml.org/lkml/2015/11/8/326),
if system wake up earlier than alarm time.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Zhuo-hao Lee <zhuo-hao.lee@intel.com>
---
 kernel/time/alarmtimer.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 7fbba63..e840ed8 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -271,11 +271,27 @@ static int alarmtimer_suspend(struct device *dev)
 		__pm_wakeup_event(ws, MSEC_PER_SEC);
 	return ret;
 }
+
+static int alarmtimer_resume(struct device *dev)
+{
+	struct rtc_device *rtc;
+
+	rtc = alarmtimer_get_rtcdev();
+	if (rtc)
+		rtc_timer_cancel(rtc, &rtctimer);
+	return 0;
+}
+
 #else
 static int alarmtimer_suspend(struct device *dev)
 {
 	return 0;
 }
+
+static int alarmtimer_resume(struct device *dev)
+{
+	return 0;
+}
 #endif
 
 static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
@@ -800,6 +816,7 @@ out:
 /* Suspend hook structures */
 static const struct dev_pm_ops alarmtimer_pm_ops = {
 	.suspend = alarmtimer_suspend,
+	.resume = alarmtimer_resume,
 };
 
 static struct platform_driver alarmtimer_driver = {
-- 
2.1.2

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#1274369 — Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3

On Tue, Nov 17, 2015 at 4:08 AM,  <zhuo-hao.lee@intel.com> wrote:
> From: zhuo-hao <zhuo-hao.lee@intel.com>
>
> Before the system go to suspend (S3), if user create a timer with clockid
> CLOCK_REALTIME_ALARM/CLOCK_BOOTTIME_ALARM and set a "large" timeout value
> to this timer. The function alarmtimer_suspend will be called to setup
> a timeout value to RTC timer to avoid the system sleep over time. However,
> if the system wakeup early than RTC timeout, the RTC timer will not be cleared.
> And this will cause the hpet_rtc_interrupt come unexpectedly until the RTC
> timeout. To fix this problem, just adding alarmtimer_resume to cancel the
> RTC timer.
>
> This was noticed because the HPET RTC emulation fires an interrupt every
> 16ms(=1/2^DEFAULT_RTC_SHIFT) up to the point where the alarm time is reached.
> This program always hits this situation(https://lkml.org/lkml/2015/11/8/326),
> if system wake up earlier than alarm time.

So thanks for the extra context here, and again I don't have an
objection to this patch.

Although from the earlier discussion it still isn't quite clear to me:
Why must the HPET RTC emulation need to fire the alarm every 16ms? Is
that not something that can be fixed?

I just want to make sure we're not hiding a deeper issue.

thanks
-john
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#1275008 — RE: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3

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#1277428 — Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3

On Fri, 20 Nov 2015, John Stultz wrote:

> On Tue, Nov 17, 2015 at 4:08 AM,  <zhuo-hao.lee@intel.com> wrote:
> > From: zhuo-hao <zhuo-hao.lee@intel.com>
> >
> > Before the system go to suspend (S3), if user create a timer with clockid
> > CLOCK_REALTIME_ALARM/CLOCK_BOOTTIME_ALARM and set a "large" timeout value
> > to this timer. The function alarmtimer_suspend will be called to setup
> > a timeout value to RTC timer to avoid the system sleep over time. However,
> > if the system wakeup early than RTC timeout, the RTC timer will not be cleared.
> > And this will cause the hpet_rtc_interrupt come unexpectedly until the RTC
> > timeout. To fix this problem, just adding alarmtimer_resume to cancel the
> > RTC timer.
> >
> > This was noticed because the HPET RTC emulation fires an interrupt every
> > 16ms(=1/2^DEFAULT_RTC_SHIFT) up to the point where the alarm time is reached.
> > This program always hits this situation(https://lkml.org/lkml/2015/11/8/326),
> > if system wake up earlier than alarm time.
> 
> So thanks for the extra context here, and again I don't have an
> objection to this patch.
> 
> Although from the earlier discussion it still isn't quite clear to me:
> Why must the HPET RTC emulation need to fire the alarm every 16ms? Is
> that not something that can be fixed?

We probably can fix it with some surgery. OTOH that stuff is fragile
as hell and I rather avoid touching it, but I won't hinder someone
brave enough doing it :)
 
> I just want to make sure we're not hiding a deeper issue.

It's not a deeper issue. It's a - admittedly dumb - implementation
detail.

Thanks,

	tglx
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#1277817 — Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3

On Wed, Nov 25, 2015 at 6:25 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Fri, 20 Nov 2015, John Stultz wrote:
>
>> On Tue, Nov 17, 2015 at 4:08 AM,  <zhuo-hao.lee@intel.com> wrote:
>> > From: zhuo-hao <zhuo-hao.lee@intel.com>
>> >
>> > Before the system go to suspend (S3), if user create a timer with clockid
>> > CLOCK_REALTIME_ALARM/CLOCK_BOOTTIME_ALARM and set a "large" timeout value
>> > to this timer. The function alarmtimer_suspend will be called to setup
>> > a timeout value to RTC timer to avoid the system sleep over time. However,
>> > if the system wakeup early than RTC timeout, the RTC timer will not be cleared.
>> > And this will cause the hpet_rtc_interrupt come unexpectedly until the RTC
>> > timeout. To fix this problem, just adding alarmtimer_resume to cancel the
>> > RTC timer.
>> >
>> > This was noticed because the HPET RTC emulation fires an interrupt every
>> > 16ms(=1/2^DEFAULT_RTC_SHIFT) up to the point where the alarm time is reached.
>> > This program always hits this situation(https://lkml.org/lkml/2015/11/8/326),
>> > if system wake up earlier than alarm time.
>>
>> So thanks for the extra context here, and again I don't have an
>> objection to this patch.
>>
>> Although from the earlier discussion it still isn't quite clear to me:
>> Why must the HPET RTC emulation need to fire the alarm every 16ms? Is
>> that not something that can be fixed?
>
> We probably can fix it with some surgery. OTOH that stuff is fragile
> as hell and I rather avoid touching it, but I won't hinder someone
> brave enough doing it :)
>
>> I just want to make sure we're not hiding a deeper issue.
>
> It's not a deeper issue. It's a - admittedly dumb - implementation
> detail.

Fair enough.. I've got it queued up for testing.

thanks
-john
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