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[PATCH] GTOD: persistent clock support

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Persistent clock support: do proper timekeeping across suspend/resume.

[bunk@stusta.de: cleanup]
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
John Stultz 2007-02-16 01:27:30 -08:00 • committed by Linus Torvalds
parent 9f907c0144
commit 411187fb05
4 changed files with 50 additions and 1 deletions
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39
kernel/timer.c
View file

@ -878,12 +878,27 @@ int timekeeping_is_continuous(void)
return ret;
}
/**
* read_persistent_clock - Return time in seconds from the persistent clock.
*
* Weak dummy function for arches that do not yet support it.
* Returns seconds from epoch using the battery backed persistent clock.
* Returns zero if unsupported.
*
* XXX - Do be sure to remove it once all arches implement it.
*/
unsigned long __attribute__((weak)) read_persistent_clock(void)
{
return 0;
}
/*
* timekeeping_init - Initializes the clocksource and common timekeeping values
*/
void __init timekeeping_init(void)
{
unsigned long flags;
unsigned long sec = read_persistent_clock();
write_seqlock_irqsave(&xtime_lock, flags);
@ -893,11 +908,20 @@ void __init timekeeping_init(void)
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
clock->cycle_last = clocksource_read(clock);
xtime.tv_sec = sec;
xtime.tv_nsec = 0;
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
write_sequnlock_irqrestore(&xtime_lock, flags);
}
/* flag for if timekeeping is suspended */
static int timekeeping_suspended;
/* time in seconds when suspend began */
static unsigned long timekeeping_suspend_time;
/**
* timekeeping_resume - Resumes the generic timekeeping subsystem.
* @dev: unused
@ -909,13 +933,25 @@ static int timekeeping_suspended;
static int timekeeping_resume(struct sys_device *dev)
{
unsigned long flags;
unsigned long now = read_persistent_clock();
write_seqlock_irqsave(&xtime_lock, flags);
/* restart the last cycle value */
if (now && (now > timekeeping_suspend_time)) {
unsigned long sleep_length = now - timekeeping_suspend_time;
xtime.tv_sec += sleep_length;
wall_to_monotonic.tv_sec -= sleep_length;
}
/* re-base the last cycle value */
clock->cycle_last = clocksource_read(clock);
clock->error = 0;
timekeeping_suspended = 0;
write_sequnlock_irqrestore(&xtime_lock, flags);
touch_softlockup_watchdog();
hrtimer_notify_resume();
return 0;
}
@ -925,6 +961,7 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
write_seqlock_irqsave(&xtime_lock, flags);
timekeeping_suspended = 1;
timekeeping_suspend_time = read_persistent_clock();
write_sequnlock_irqrestore(&xtime_lock, flags);
return 0;
}