[patch 02/21] GTOD: persistent clock support, core

[Thomas Gleixner <tglx@linutronix.de>]

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          |   34 +++++++++++++++++++++++++++++++---
 4 files changed, 43 insertions(+), 3 deletions(-)

linux-2.6.18-rc6_timeofday-persistent-clock-generic_C6.patch
Index: linux-2.6.18-mm2/include/linux/hrtimer.h
===================================================================
--- linux-2.6.18-mm2.orig/include/linux/hrtimer.h	2006-10-02 00:55:49.000000000 +0200
+++ linux-2.6.18-mm2/include/linux/hrtimer.h	2006-10-02 00:55:50.000000000 +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-mm2/include/linux/time.h
===================================================================
--- linux-2.6.18-mm2.orig/include/linux/time.h	2006-10-02 00:55:49.000000000 +0200
+++ linux-2.6.18-mm2/include/linux/time.h	2006-10-02 00:55:50.000000000 +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-mm2/kernel/hrtimer.c
===================================================================
--- linux-2.6.18-mm2.orig/kernel/hrtimer.c	2006-10-02 00:55:49.000000000 +0200
+++ linux-2.6.18-mm2/kernel/hrtimer.c	2006-10-02 00:55:50.000000000 +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-mm2/kernel/timer.c
===================================================================
--- linux-2.6.18-mm2.orig/kernel/timer.c	2006-10-02 00:55:50.000000000 +0200
+++ linux-2.6.18-mm2/kernel/timer.c	2006-10-02 00:55:50.000000000 +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 +746,20 @@ int timekeeping_is_continuous(void)
 	return ret;
 }
 
+/* Weak dummy function for arches that do not yet support it.
+ * 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 flags, sec = read_persistent_clock();
 
 	write_seqlock_irqsave(&xtime_lock, flags);
 
@@ -758,11 +769,18 @@ void __init timekeeping_init(void)
 	clocksource_calculate_interval(clock, tick_nsec);
 	clock->cycle_last = clocksource_read(clock);
 
+	xtime.tv_sec = sec;
+	xtime.tv_nsec = (jiffies % HZ) * (NSEC_PER_SEC / HZ);
+	set_normalized_timespec(&wall_to_monotonic,
+		-xtime.tv_sec, -xtime.tv_nsec);
+
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 }
 
 
 static int timekeeping_suspended;
+static unsigned long timekeeping_suspend_time;
+
 /**
  * timekeeping_resume - Resumes the generic timekeeping subsystem.
  * @dev:	unused
@@ -773,14 +791,23 @@ static int timekeeping_suspended;
  */
 static int timekeeping_resume(struct sys_device *dev)
 {
-	unsigned long flags;
+	unsigned long flags, 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 += 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 +817,7 @@ 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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