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Commit 6a8943d9 authored by Arve Hjønnevåg's avatar Arve Hjønnevåg Committed by John Stultz
Browse files

rtc: Fix some bugs that allowed accumulating time drift in suspend/resume 



The current code checks if abs(delta_delta.tv_sec) is greater or
equal to two before it discards the old delta value, but this can
trigger at close to -1 seconds since -1.000000001 seconds is stored
as tv_sec -2 and tv_nsec 999999999 in a normalized timespec.

rtc_resume had an early return check if the rtc value had not changed
since rtc_suspend. This effectivly stops time for the duration of the
short sleep. Check if sleep_time is positive after all the adjustments
have been applied instead since this allows the old_system adjustment
in rtc_suspend to have an effect even for short sleep cycles.

CC: stable@kernel.org
Signed-off-by: default avatarArve Hjønnevåg <arve@android.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent c0afabd3

drivers/rtc/class.c

+5 −5
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ static int rtc_suspend(struct device *dev, pm_message_t mesg) 
	 */

	delta = timespec_sub(old_system, old_rtc);

	delta_delta = timespec_sub(delta, old_delta);

	if (abs(delta_delta.tv_sec)  >= 2) {

	if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {

		/*

		 * if delta_delta is too large, assume time correction

		 * has occured and set old_delta to the current delta.
@@ -100,8 +100,7 @@ static int rtc_resume(struct device *dev) 
	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)

	if (new_rtc.tv_sec < old_rtc.tv_sec) {

		pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));

		return 0;

	}
@@ -119,6 +118,7 @@ static int rtc_resume(struct device *dev) 
	sleep_time = timespec_sub(sleep_time,

			timespec_sub(new_system, old_system));



	if (sleep_time.tv_sec >= 0)

		timekeeping_inject_sleeptime(&sleep_time);

	return 0;

}