3 files changed, 63 insertions, 17 deletions

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 39013867cbd6..4194e59e14cd 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;
 }
 
diff --git a/include/linux/time.h b/include/linux/time.h
index 454a26205787..4ea5a75fcacd 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -126,6 +126,7 @@ struct timespec __current_kernel_time(void); /* does not take xtime_lock */
 struct timespec get_monotonic_coarse(void);
 void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
                                 struct timespec *wtom, struct timespec *sleep);
+void timekeeping_inject_sleeptime(struct timespec *delta);
 
 #define CURRENT_TIME            (current_kernel_time())
 #define CURRENT_TIME_SEC        ((struct timespec) { get_seconds(), 0 })
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 8ad5d576755e..8e6a05a5915a 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -596,6 +596,58 @@ void __init timekeeping_init(void)
 static struct timespec timekeeping_suspend_time;
 
 /**
+ * __timekeeping_inject_sleeptime - Internal function to add sleep interval
+ * @delta: pointer to a timespec delta value
+ *
+ * Takes a timespec offset measuring a suspend interval and properly
+ * adds the sleep offset to the timekeeping variables.
+ */
+static void __timekeeping_inject_sleeptime(struct timespec *delta)
+{
+        xtime = timespec_add(xtime, *delta);
+        wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
+        total_sleep_time = timespec_add(total_sleep_time, *delta);
+}
+
+
+/**
+ * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
+ * @delta: pointer to a timespec delta value
+ *
+ * This hook is for architectures that cannot support read_persistent_clock
+ * because their RTC/persistent clock is only accessible when irqs are enabled.
+ *
+ * This function should only be called by rtc_resume(), and allows
+ * a suspend offset to be injected into the timekeeping values.
+ */
+void timekeeping_inject_sleeptime(struct timespec *delta)
+{
+        unsigned long flags;
+        struct timespec ts;
+
+        /* Make sure we don't set the clock twice */
+        read_persistent_clock(&ts);
+        if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
+                return;
+
+        write_seqlock_irqsave(&xtime_lock, flags);
+        timekeeping_forward_now();
+
+        __timekeeping_inject_sleeptime(delta);
+
+        timekeeper.ntp_error = 0;
+        ntp_clear();
+        update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
+                                timekeeper.mult);
+
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
+        /* signal hrtimers about time change */
+        clock_was_set();
+}
+
+
+/**
  * timekeeping_resume - Resumes the generic timekeeping subsystem.
  *
  * This is for the generic clocksource timekeeping.
@@ -615,9 +667,7 @@ static void timekeeping_resume(void)
 
         if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
                 ts = timespec_sub(ts, timekeeping_suspend_time);
-                xtime = timespec_add(xtime, ts);
-                wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
-                total_sleep_time = timespec_add(total_sleep_time, ts);
+                __timekeeping_inject_sleeptime(&ts);
         }
         /* re-base the last cycle value */
         timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);