clocksource/drivers/tegra: Provide y2038-safe tegra_read_persistent_clock() replacement

As part of addressing "y2038 problem" for in-kernel uses, this
patch adds the y2038-safe tegra_read_persistent_clock64() using
timespec64.

Because we rely on some subsequent changes to convert arm
multiarch support, tegra_read_persistent_clock() will be removed
then.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-6-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/clocksource/tegra20_timer.c

@@ -51,7 +51,7 @@
 static void __iomem *timer_reg_base;
 static void __iomem *rtc_base;
 
-static struct timespec persistent_ts;
+static struct timespec64 persistent_ts;
 static u64 persistent_ms, last_persistent_ms;
 
 static struct delay_timer tegra_delay_timer;
@@ -120,26 +120,33 @@ static u64 tegra_rtc_read_ms(void)
 }
 
 /*
- * tegra_read_persistent_clock -  Return time from a persistent clock.
+ * tegra_read_persistent_clock64 -  Return time from a persistent clock.
  *
  * Reads the time from a source which isn't disabled during PM, the
  * 32k sync timer.  Convert the cycles elapsed since last read into
- * nsecs and adds to a monotonically increasing timespec.
+ * nsecs and adds to a monotonically increasing timespec64.
  * Care must be taken that this funciton is not called while the
  * tegra_rtc driver could be executing to avoid race conditions
  * on the RTC shadow register
  */
-static void tegra_read_persistent_clock(struct timespec *ts)
+static void tegra_read_persistent_clock64(struct timespec64 *ts)
 {
 	u64 delta;
-	struct timespec *tsp = &persistent_ts;
 
 	last_persistent_ms = persistent_ms;
 	persistent_ms = tegra_rtc_read_ms();
 	delta = persistent_ms - last_persistent_ms;
 
-	timespec_add_ns(tsp, delta * NSEC_PER_MSEC);
-	*ts = *tsp;
+	timespec64_add_ns(&persistent_ts, delta * NSEC_PER_MSEC);
+	*ts = persistent_ts;
+}
+
+static void tegra_read_persistent_clock(struct timespec *ts)
+{
+	struct timespec ts64;
+
+	tegra_read_persistent_clock64(&ts64);
+	*ts = timespec64_to_timespec(ts64);
 }
 
 static unsigned long tegra_delay_timer_read_counter_long(void)