time: Add timekeeping_inject_sleeptime

Some platforms cannot implement read_persistent_clock, as
their RTC devices are only accessible when interrupts are enabled.
This keeps them from being used by the timekeeping code on resume
to measure the time in suspend.

The RTC layer tries to work around this, by calling do_settimeofday
on resume after irqs are reenabled to set the time properly. However,
this only corrects CLOCK_REALTIME, and does not properly adjust
the sleep time value. This causes btime in /proc/stat to be incorrect
as well as making the new CLOCK_BOTTTIME inaccurate.

This patch resolves the issue by introducing a new timekeeping hook
to allow the RTC layer to inject the sleep time on resume.

The code also checks to make sure that read_persistent_clock is
nonfunctional before setting the sleep time, so that should the RTC's
HCTOSYS option be configured in on a system that does support
read_persistent_clock we will not increase the total_sleep_time twice.

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 9 insertions, 14 deletions

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 39013867cbd..4194e59e14c 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -41,26 +41,21 @@ static void rtc_device_release(struct device *dev)
  * system's wall clock; restore it on resume().
  */
 
-static struct timespec	delta;
 static time_t		oldtime;
+static struct timespec	oldts;
 
 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();
 
 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
 		return 0;
 
 	rtc_read_time(rtc, &tm);
+	ktime_get_ts(&oldts);
 	rtc_tm_to_time(&tm, &oldtime);
 
-	/* RTC precision is 1 second; adjust delta for avg 1/2 sec err */
-	set_normalized_timespec(&delta,
-				ts.tv_sec - oldtime,
-				ts.tv_nsec - (NSEC_PER_SEC >> 1));
-
 	return 0;
 }
 
@@ -70,10 +65,12 @@ static int rtc_resume(struct device *dev)
 	struct rtc_time		tm;
 	time_t			newtime;
 	struct timespec		time;
+	struct timespec		newts;
 
 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
 		return 0;
 
+	ktime_get_ts(&newts);
 	rtc_read_time(rtc, &tm);
 	if (rtc_valid_tm(&tm) != 0) {
 		pr_debug("%s:  bogus resume time\n", dev_name(&rtc->dev));
@@ -85,15 +82,13 @@ static int rtc_resume(struct device *dev)
 			pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));
 		return 0;
 	}
+	/* calculate the RTC time delta */
+	set_normalized_timespec(&time, newtime - oldtime, 0);
 
-	/* restore wall clock using delta against this RTC;
-	 * adjust again for avg 1/2 second RTC sampling error
-	 */
-	set_normalized_timespec(&time,
-				newtime + delta.tv_sec,
-				(NSEC_PER_SEC >> 1) + delta.tv_nsec);
-	do_settimeofday(&time);
+	/* subtract kernel time between rtc_suspend to rtc_resume */
+	time = timespec_sub(time, timespec_sub(newts, oldts));
 
+	timekeeping_inject_sleeptime(&time);
 	return 0;
 }