ANDROID: power: wakeup_reason: fix suspend time reporting

Suspend time reporting Change-Id: I2cb9a9408a5fd12166aaec11b935a0fd6a408c63
(Power: Report suspend times from last_suspend_time), is broken on 3.16+
kernels because get_xtime_and_monotonic_and_sleep_offset() hrtimer helper
routine is removed from kernel timekeeping.

The replacement helper routines ktime_get_update_offsets_{tick,now}()
are private to core kernel timekeeping so we can't use them, hence using
ktime_get() and ktime_get_boottime() instead and sampling the time twice.

Idea is to use Monotonic boottime offset to calculate total time spent
in last suspend state and CLOCK_MONOTONIC to calculate time spent in
last suspend-resume process.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

kernel/power/wakeup_reason.c

@@ -36,10 +36,10 @@ static char abort_reason[MAX_SUSPEND_ABORT_LEN];
 static struct kobject *wakeup_reason;
 static spinlock_t resume_reason_lock;
 
-static struct timespec last_xtime; /* wall time before last suspend */
+static ktime_t last_monotime; /* monotonic time before last suspend */
-static struct timespec curr_xtime; /* wall time after last suspend */
+static ktime_t curr_monotime; /* monotonic time after last suspend */
-static struct timespec last_stime; /* total_sleep_time before last suspend */
+static ktime_t last_stime; /* monotonic boottime offset before last suspend */
-static struct timespec curr_stime; /* total_sleep_time after last suspend */
+static ktime_t curr_stime; /* monotonic boottime offset after last suspend */
 
 static ssize_t last_resume_reason_show(struct kobject *kobj, struct kobj_attribute *attr,
 		char *buf)
@@ -71,14 +71,22 @@ static ssize_t last_suspend_time_show(struct kobject *kobj,
 	struct timespec total_time;
 	struct timespec suspend_resume_time;
 
-	sleep_time = timespec_sub(curr_stime, last_stime);
+	/*
-	total_time = timespec_sub(curr_xtime, last_xtime);
+	 * total_time is calculated from monotonic bootoffsets because
-	suspend_resume_time = timespec_sub(total_time, sleep_time);
+	 * unlike CLOCK_MONOTONIC it include the time spent in suspend state.
+	 */
+	total_time = ktime_to_timespec(ktime_sub(curr_stime, last_stime));
 
 	/*
-	 * suspend_resume_time is calculated from sleep_time. Userspace would
+	 * suspend_resume_time is calculated as monotonic (CLOCK_MONOTONIC)
-	 * always need both. Export them in pair here.
+	 * time interval before entering suspend and post suspend.
 	 */
+	suspend_resume_time = ktime_to_timespec(ktime_sub(curr_monotime, last_monotime));
+
+	/* sleep_time = total_time - suspend_resume_time */
+	sleep_time = timespec_sub(total_time, suspend_resume_time);
+
+	/* Export suspend_resume_time and sleep_time in pair here. */
 	return sprintf(buf, "%lu.%09lu %lu.%09lu\n",
 				suspend_resume_time.tv_sec, suspend_resume_time.tv_nsec,
 				sleep_time.tv_sec, sleep_time.tv_nsec);
@@ -145,21 +153,22 @@ void log_suspend_abort_reason(const char *fmt, ...)
 static int wakeup_reason_pm_event(struct notifier_block *notifier,
 		unsigned long pm_event, void *unused)
 {
-	struct timespec xtom; /* wall_to_monotonic, ignored */
-
 	switch (pm_event) {
 	case PM_SUSPEND_PREPARE:
 		spin_lock(&resume_reason_lock);
 		irqcount = 0;
 		suspend_abort = false;
 		spin_unlock(&resume_reason_lock);
-
+		/* monotonic time since boot */
-		get_xtime_and_monotonic_and_sleep_offset(&last_xtime, &xtom,
+		last_monotime = ktime_get();
-			&last_stime);
+		/* monotonic time since boot including the time spent in suspend */
+		last_stime = ktime_get_boottime();
 		break;
 	case PM_POST_SUSPEND:
-		get_xtime_and_monotonic_and_sleep_offset(&curr_xtime, &xtom,
+		/* monotonic time since boot */
-			&curr_stime);
+		curr_monotime = ktime_get();
+		/* monotonic time since boot including the time spent in suspend */
+		curr_stime = ktime_get_boottime();
 		break;
 	default:
 		break;