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-rw-r--r--kernel/time/timekeeping.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 9d09777a213f..fdc6b887b208 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -692,12 +692,34 @@ static void timekeeping_resume(void)
static int timekeeping_suspend(void)
{
unsigned long flags;
+ struct timespec delta, delta_delta;
+ static struct timespec old_delta;
read_persistent_clock(&timekeeping_suspend_time);
write_seqlock_irqsave(&xtime_lock, flags);
timekeeping_forward_now();
timekeeping_suspended = 1;
+
+ /*
+ * To avoid drift caused by repeated suspend/resumes,
+ * which each can add ~1 second drift error,
+ * try to compensate so the difference in system time
+ * and persistent_clock time stays close to constant.
+ */
+ delta = timespec_sub(xtime, timekeeping_suspend_time);
+ delta_delta = timespec_sub(delta, old_delta);
+ if (abs(delta_delta.tv_sec) >= 2) {
+ /*
+ * if delta_delta is too large, assume time correction
+ * has occured and set old_delta to the current delta.
+ */
+ old_delta = delta;
+ } else {
+ /* Otherwise try to adjust old_system to compensate */
+ timekeeping_suspend_time =
+ timespec_add(timekeeping_suspend_time, delta_delta);
+ }
write_sequnlock_irqrestore(&xtime_lock, flags);
clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);