staging: android-alarm: Convert ALARM_ELAPSED_REALTIME to use CLOCK_BOOTTIME

The ALARM_ELAPSED_REALTIME clock domain in Android pointed
to the need for something similar in linux system-wide
(instead of limited to just the alarm interface).

Thus CLOCK_BOOTTIME was introduced into the upstream kernel
in 2.6.39.

This patch attempts to convert the android alarm timer to utilize
the kernel's CLOCK_BOOTTIME clockid for ALARM_ELAPSED_REALTIME,
instead of managing it itself.

CC: Colin Cross <ccross@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Android Kernel Team <kernel-team@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 22 insertions, 58 deletions

diff --git a/drivers/staging/android/alarm-dev.c b/drivers/staging/android/alarm-dev.c
index 1b618f328115..3840ca22d835 100644
--- a/drivers/staging/android/alarm-dev.c
+++ b/drivers/staging/android/alarm-dev.c
@@ -179,8 +179,7 @@ from_old_alarm_set:
                         break;
                 case ANDROID_ALARM_ELAPSED_REALTIME_WAKEUP:
                 case ANDROID_ALARM_ELAPSED_REALTIME:
-                        tmp_time =
-                                ktime_to_timespec(alarm_get_elapsed_realtime());
+                        get_monotonic_boottime(&tmp_time);
                         break;
                 case ANDROID_ALARM_TYPE_COUNT:
                 case ANDROID_ALARM_SYSTEMTIME:
diff --git a/drivers/staging/android/alarm.c b/drivers/staging/android/alarm.c
index 0cae132fbfd7..22b18d1f1fe8 100644
--- a/drivers/staging/android/alarm.c
+++ b/drivers/staging/android/alarm.c
@@ -65,7 +65,6 @@ struct alarm_queue {
         struct rb_root alarms;
         struct rb_node *first;
         struct hrtimer timer;
-        ktime_t delta;
         bool stopped;
         ktime_t stopped_time;
 };
@@ -107,8 +106,8 @@ static void update_timer_locked(struct alarm_queue *base, bool head_removed)
         }
 
         hrtimer_try_to_cancel(&base->timer);
-        base->timer.node.expires = ktime_add(base->delta, alarm->expires);
-        base->timer._softexpires = ktime_add(base->delta, alarm->softexpires);
+        base->timer.node.expires = alarm->expires;
+        base->timer._softexpires = alarm->softexpires;
         hrtimer_start_expires(&base->timer, HRTIMER_MODE_ABS);
 }
 
@@ -279,10 +278,6 @@ int android_alarm_set_rtc(struct timespec new_time)
                 alarms[i].stopped = true;
                 alarms[i].stopped_time = timespec_to_ktime(tmp_time);
         }
-        alarms[ANDROID_ALARM_ELAPSED_REALTIME_WAKEUP].delta =
-                alarms[ANDROID_ALARM_ELAPSED_REALTIME].delta =
-                ktime_sub(alarms[ANDROID_ALARM_ELAPSED_REALTIME].delta,
-                        timespec_to_ktime(timespec_sub(tmp_time, new_time)));
         spin_unlock_irqrestore(&alarm_slock, flags);
         ret = do_settimeofday(&new_time);
         spin_lock_irqsave(&alarm_slock, flags);
@@ -310,24 +305,6 @@ err:
         return ret;
 }
 
-/**
- * alarm_get_elapsed_realtime - get the elapsed real time in ktime_t format
- *
- * returns the time in ktime_t format
- */
-ktime_t alarm_get_elapsed_realtime(void)
-{
-        ktime_t now;
-        unsigned long flags;
-        struct alarm_queue *base = &alarms[ANDROID_ALARM_ELAPSED_REALTIME];
-
-        spin_lock_irqsave(&alarm_slock, flags);
-        now = base->stopped ? base->stopped_time : ktime_get_real();
-        now = ktime_sub(now, base->delta);
-        spin_unlock_irqrestore(&alarm_slock, flags);
-        return now;
-}
-
 static enum hrtimer_restart alarm_timer_triggered(struct hrtimer *timer)
 {
         struct alarm_queue *base;
@@ -339,7 +316,6 @@ static enum hrtimer_restart alarm_timer_triggered(struct hrtimer *timer)
 
         base = container_of(timer, struct alarm_queue, timer);
         now = base->stopped ? base->stopped_time : hrtimer_cb_get_time(timer);
-        now = ktime_sub(now, base->delta);
 
         pr_alarm(INT, "alarm_timer_triggered type %td at %lld\n",
                 base - alarms, ktime_to_ns(now));
@@ -536,40 +512,25 @@ static struct platform_driver alarm_driver = {
         }
 };
 
-static int __init alarm_late_init(void)
-{
-        unsigned long   flags;
-        struct timespec tmp_time, system_time;
-
-        /* this needs to run after the rtc is read at boot */
-        spin_lock_irqsave(&alarm_slock, flags);
-        /* We read the current rtc and system time so we can later calculate
-         * elasped realtime to be (boot_systemtime + rtc - boot_rtc) ==
-         * (rtc - (boot_rtc - boot_systemtime))
-         */
-        getnstimeofday(&tmp_time);
-        ktime_get_ts(&system_time);
-        alarms[ANDROID_ALARM_ELAPSED_REALTIME_WAKEUP].delta =
-                alarms[ANDROID_ALARM_ELAPSED_REALTIME].delta =
-                        timespec_to_ktime(timespec_sub(tmp_time, system_time));
-
-        spin_unlock_irqrestore(&alarm_slock, flags);
-        return 0;
-}
-
 static int __init alarm_driver_init(void)
 {
         int err;
         int i;
 
-        for (i = 0; i < ANDROID_ALARM_SYSTEMTIME; i++) {
-                hrtimer_init(&alarms[i].timer,
-                                CLOCK_REALTIME, HRTIMER_MODE_ABS);
-                alarms[i].timer.function = alarm_timer_triggered;
-        }
+        hrtimer_init(&alarms[ANDROID_ALARM_RTC_WAKEUP].timer,
+                        CLOCK_REALTIME, HRTIMER_MODE_ABS);
+        hrtimer_init(&alarms[ANDROID_ALARM_RTC].timer,
+                        CLOCK_REALTIME, HRTIMER_MODE_ABS);
+        hrtimer_init(&alarms[ANDROID_ALARM_ELAPSED_REALTIME_WAKEUP].timer,
+                        CLOCK_BOOTTIME, HRTIMER_MODE_ABS);
+        hrtimer_init(&alarms[ANDROID_ALARM_ELAPSED_REALTIME].timer,
+                        CLOCK_BOOTTIME, HRTIMER_MODE_ABS);
         hrtimer_init(&alarms[ANDROID_ALARM_SYSTEMTIME].timer,
-                     CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
-        alarms[ANDROID_ALARM_SYSTEMTIME].timer.function = alarm_timer_triggered;
+                        CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+
+        for (i = 0; i < ANDROID_ALARM_TYPE_COUNT; i++)
+                alarms[i].timer.function = alarm_timer_triggered;
+
         err = platform_driver_register(&alarm_driver);
         if (err < 0)
                 goto err1;
@@ -595,7 +556,6 @@ static void  __exit alarm_exit(void)
         platform_driver_unregister(&alarm_driver);
 }
 
-late_initcall(alarm_late_init);
 module_init(alarm_driver_init);
 module_exit(alarm_exit);
 
diff --git a/drivers/staging/android/android_alarm.h b/drivers/staging/android/android_alarm.h
index e586caef4ba8..a1121772bc2e 100644
--- a/drivers/staging/android/android_alarm.h
+++ b/drivers/staging/android/android_alarm.h
@@ -37,6 +37,7 @@ enum android_alarm_type {
 
 #include <linux/ktime.h>
 #include <linux/rbtree.h>
+#include <linux/hrtimer.h>
 
 /*
  * The alarm interface is similar to the hrtimer interface but adds support
@@ -71,7 +72,11 @@ void android_alarm_start_range(struct android_alarm *alarm, ktime_t start,
                                                                 ktime_t end);
 int android_alarm_try_to_cancel(struct android_alarm *alarm);
 int android_alarm_cancel(struct android_alarm *alarm);
-ktime_t alarm_get_elapsed_realtime(void);
+
+static inline ktime_t alarm_get_elapsed_realtime(void)
+{
+        return ktime_get_boottime();
+}
 
 /* set rtc while preserving elapsed realtime */
 int android_alarm_set_rtc(const struct timespec ts);