From: Arve Hjønnevåg <arve@android.com>
Date: Sat, 26 Jul 2008 03:58:15 +0000 (-0700)
Subject: rtc: Try to prevent RTC errors from accumulating.
X-Git-Tag: firefly_0821_release~11755
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=65a84712596bfd5b0831b8a09691ad3eca391ade;p=firefly-linux-kernel-4.4.55.git

rtc: Try to prevent RTC errors from accumulating.

When we resume we only know how many whole seconds has elapsed.
These errors would accumulate in delta. We now only set the delta
if it would change by more than two seconds. If we drift back by
by more than a second add one in resume.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index be5a6b73e601..2bc9ef37b46f 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -40,25 +40,32 @@ static void rtc_device_release(struct device *dev)
  */
 
 static struct timespec	delta;
+static struct timespec	delta_delta;
 static time_t		oldtime;
 
 static int rtc_suspend(struct device *dev, pm_message_t mesg)
 {
 	struct rtc_device	*rtc = to_rtc_device(dev);
 	struct rtc_time		tm;
-	struct timespec		ts = current_kernel_time();
+	struct timespec		ts;
+	struct timespec		new_delta;
 
 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
 		return 0;
 
+	getnstimeofday(&ts);
 	rtc_read_time(rtc, &tm);
 	rtc_tm_to_time(&tm, &oldtime);
 
 	/* RTC precision is 1 second; adjust delta for avg 1/2 sec err */
-	set_normalized_timespec(&delta,
+	set_normalized_timespec(&new_delta,
 				ts.tv_sec - oldtime,
 				ts.tv_nsec - (NSEC_PER_SEC >> 1));
 
+	/* prevent 1/2 sec errors from accumulating */
+	delta_delta = timespec_sub(new_delta, delta);
+	if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2)
+		delta = new_delta;
 	return 0;
 }
 
@@ -78,6 +85,8 @@ static int rtc_resume(struct device *dev)
 		return 0;
 	}
 	rtc_tm_to_time(&tm, &newtime);
+	if (delta_delta.tv_sec < -1)
+		newtime++;
 	if (newtime <= oldtime) {
 		if (newtime < oldtime)
 			pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));