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Subject[patch 02/22] GTOD: persistent clock support, core
From: John Stultz <johnstul@us.ibm.com>

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

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>
include/linux/hrtimer.h | 3 +++
include/linux/time.h | 1 +
kernel/hrtimer.c | 8 ++++++++
kernel/timer.c | 40 +++++++++++++++++++++++++++++++++++++++-
4 files changed, 51 insertions(+), 1 deletion(-)
Index: linux-2.6.18-mm3/include/linux/hrtimer.h
===================================================================
--- linux-2.6.18-mm3.orig/include/linux/hrtimer.h 2006-10-04 18:13:53.000000000 +0200
+++ linux-2.6.18-mm3/include/linux/hrtimer.h 2006-10-04 18:13:54.000000000 +0200
@@ -146,6 +146,9 @@ extern void hrtimer_init_sleeper(struct
/* Soft interrupt function to run the hrtimer queues: */
extern void hrtimer_run_queues(void);

+/* Resume notification */
+void hrtimer_notify_resume(void);
+
/* Bootup initialization: */
extern void __init hrtimers_init(void);

Index: linux-2.6.18-mm3/include/linux/time.h
===================================================================
--- linux-2.6.18-mm3.orig/include/linux/time.h 2006-10-04 18:13:53.000000000 +0200
+++ linux-2.6.18-mm3/include/linux/time.h 2006-10-04 18:13:54.000000000 +0200
@@ -92,6 +92,7 @@ extern struct timespec xtime;
extern struct timespec wall_to_monotonic;
extern seqlock_t xtime_lock;

+extern unsigned long read_persistent_clock(void);
void timekeeping_init(void);

static inline unsigned long get_seconds(void)
Index: linux-2.6.18-mm3/kernel/hrtimer.c
===================================================================
--- linux-2.6.18-mm3.orig/kernel/hrtimer.c 2006-10-04 18:13:53.000000000 +0200
+++ linux-2.6.18-mm3/kernel/hrtimer.c 2006-10-04 18:13:54.000000000 +0200
@@ -287,6 +287,14 @@ static unsigned long ktime_divns(const k
#endif /* BITS_PER_LONG >= 64 */

/*
+ * Timekeeping resumed notification
+ */
+void hrtimer_notify_resume(void)
+{
+ clock_was_set();
+}
+
+/*
* Counterpart to lock_timer_base above:
*/
static inline
Index: linux-2.6.18-mm3/kernel/timer.c
===================================================================
--- linux-2.6.18-mm3.orig/kernel/timer.c 2006-10-04 18:13:53.000000000 +0200
+++ linux-2.6.18-mm3/kernel/timer.c 2006-10-04 18:13:54.000000000 +0200
@@ -41,6 +41,9 @@
#include <asm/timex.h>
#include <asm/io.h>

+/* jiffies at the most recent update of wall time */
+unsigned long wall_jiffies = INITIAL_JIFFIES;
+
u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;

EXPORT_SYMBOL(jiffies_64);
@@ -743,12 +746,27 @@ 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);

@@ -758,11 +776,20 @@ void __init timekeeping_init(void)
clocksource_calculate_interval(clock, tick_nsec);
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
@@ -774,13 +801,23 @@ 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;
+ jiffies_64 += (u64)sleep_length * HZ;
+ }
+ /* re-base the last cycle value */
clock->cycle_last = clocksource_read(clock);
clock->error = 0;
timekeeping_suspended = 0;
write_sequnlock_irqrestore(&xtime_lock, flags);
+
+ hrtimer_notify_resume();
+
return 0;
}

@@ -790,6 +827,7 @@ static int timekeeping_suspend(struct sy

write_seqlock_irqsave(&xtime_lock, flags);
timekeeping_suspended = 1;
+ timekeeping_suspend_time = read_persistent_clock();
write_sequnlock_irqrestore(&xtime_lock, flags);
return 0;
}
--

-
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