1 files changed, 80 insertions, 13 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index eb97371b87d8fa..524c7f63836554 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -792,24 +792,93 @@ u64 current_tick_length(void)
 	return ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj;
 }
 
+/* XXX - all of this timekeeping code should be later moved to time.c */
+#include <linux/clocksource.h>
+static struct clocksource *clock; /* pointer to current clocksource */
+static cycle_t last_clock_cycle;  /* cycle value at last update_wall_time */
 /*
- * Using a loop looks inefficient, but "ticks" is
- * usually just one (we shouldn't be losing ticks,
- * we're doing this this way mainly for interrupt
- * latency reasons, not because we think we'll
- * have lots of lost timer ticks
+ * timekeeping_init - Initializes the clocksource and common timekeeping values
  */
-static void update_wall_time(unsigned long ticks)
+void __init timekeeping_init(void)
 {
-	do {
-		ticks--;
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	clock = get_next_clocksource();
+	calculate_clocksource_interval(clock, tick_nsec);
+	last_clock_cycle = read_clocksource(clock);
+	ntp_clear();
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
+
+/*
+ * timekeeping_resume - Resumes the generic timekeeping subsystem.
+ * @dev:	unused
+ *
+ * This is for the generic clocksource timekeeping.
+ * xtime/wall_to_monotonic/jiffies/wall_jiffies/etc are
+ * still managed by arch specific suspend/resume code.
+ */
+static int timekeeping_resume(struct sys_device *dev)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	/* restart the last cycle value */
+	last_clock_cycle = read_clocksource(clock);
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+	return 0;
+}
+
+/* sysfs resume/suspend bits for timekeeping */
+static struct sysdev_class timekeeping_sysclass = {
+	.resume		= timekeeping_resume,
+	set_kset_name("timekeeping"),
+};
+
+static struct sys_device device_timer = {
+	.id		= 0,
+	.cls		= &timekeeping_sysclass,
+};
+
+static int __init timekeeping_init_device(void)
+{
+	int error = sysdev_class_register(&timekeeping_sysclass);
+	if (!error)
+		error = sysdev_register(&device_timer);
+	return error;
+}
+
+device_initcall(timekeeping_init_device);
+
+/*
+ * update_wall_time - Uses the current clocksource to increment the wall time
+ *
+ * Called from the timer interrupt, must hold a write on xtime_lock.
+ */
+static void update_wall_time(void)
+{
+	cycle_t now, offset;
+
+	now = read_clocksource(clock);
+	offset = (now - last_clock_cycle)&clock->mask;
+
+	/* normally this loop will run just once, however in the
+	 * case of lost or late ticks, it will accumulate correctly.
+	 */
+	while (offset > clock->interval_cycles) {
+		/* accumulate one interval */
+		last_clock_cycle += clock->interval_cycles;
+		offset -= clock->interval_cycles;
+
 		update_wall_time_one_tick();
 		if (xtime.tv_nsec >= 1000000000) {
 			xtime.tv_nsec -= 1000000000;
 			xtime.tv_sec++;
 			second_overflow();
 		}
-	} while (ticks);
+	}
 }
 
 /*
@@ -915,10 +984,8 @@ static inline void update_times(void)
 	unsigned long ticks;
 
 	ticks = jiffies - wall_jiffies;
-	if (ticks) {
-		wall_jiffies += ticks;
-		update_wall_time(ticks);
-	}
+	wall_jiffies += ticks;
+	update_wall_time();
 	calc_load(ticks);
 }