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path: root/drivers/rtc/class.c
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Diffstat (limited to 'drivers/rtc/class.c')
-rw-r--r--drivers/rtc/class.c65
1 files changed, 48 insertions, 17 deletions
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 4194e59..01a7df53 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -41,20 +41,41 @@ static void rtc_device_release(struct device *dev)
* system's wall clock; restore it on resume().
*/
-static time_t oldtime;
-static struct timespec oldts;
+static struct timespec old_rtc, old_system, old_delta;
+
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 delta, delta_delta;
if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
return 0;
+ /* snapshot the current RTC and system time at suspend*/
rtc_read_time(rtc, &tm);
- ktime_get_ts(&oldts);
- rtc_tm_to_time(&tm, &oldtime);
+ getnstimeofday(&old_system);
+ rtc_tm_to_time(&tm, &old_rtc.tv_sec);
+
+
+ /*
+ * 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 rtc time stays close to constant.
+ */
+ delta = timespec_sub(old_system, old_rtc);
+ 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 */
+ old_system = timespec_sub(old_system, delta_delta);
+ }
return 0;
}
@@ -63,32 +84,42 @@ static int rtc_resume(struct device *dev)
{
struct rtc_device *rtc = to_rtc_device(dev);
struct rtc_time tm;
- time_t newtime;
- struct timespec time;
- struct timespec newts;
+ struct timespec new_system, new_rtc;
+ struct timespec sleep_time;
if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
return 0;
- ktime_get_ts(&newts);
+ /* snapshot the current rtc and system time at resume */
+ getnstimeofday(&new_system);
rtc_read_time(rtc, &tm);
if (rtc_valid_tm(&tm) != 0) {
pr_debug("%s: bogus resume time\n", dev_name(&rtc->dev));
return 0;
}
- rtc_tm_to_time(&tm, &newtime);
- if (newtime <= oldtime) {
- if (newtime < oldtime)
+ rtc_tm_to_time(&tm, &new_rtc.tv_sec);
+ new_rtc.tv_nsec = 0;
+
+ if (new_rtc.tv_sec <= old_rtc.tv_sec) {
+ if (new_rtc.tv_sec < old_rtc.tv_sec)
pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
return 0;
}
- /* calculate the RTC time delta */
- set_normalized_timespec(&time, newtime - oldtime, 0);
- /* subtract kernel time between rtc_suspend to rtc_resume */
- time = timespec_sub(time, timespec_sub(newts, oldts));
+ /* calculate the RTC time delta (sleep time)*/
+ sleep_time = timespec_sub(new_rtc, old_rtc);
+
+ /*
+ * Since these RTC suspend/resume handlers are not called
+ * at the very end of suspend or the start of resume,
+ * some run-time may pass on either sides of the sleep time
+ * so subtract kernel run-time between rtc_suspend to rtc_resume
+ * to keep things accurate.
+ */
+ sleep_time = timespec_sub(sleep_time,
+ timespec_sub(new_system, old_system));
- timekeeping_inject_sleeptime(&time);
+ timekeeping_inject_sleeptime(&sleep_time);
return 0;
}