timekeeping: Add more coarse clocktai/boottime interfaces

The set of APIs we provide has a few holes for coarse times, e.g. we
provide ktime_get_coarse_boottime() and ktime_get_boottime_ts64(),
but not the combination of the two.

This adds four new functions:

ktime_get_coarse_boottime_ts64()
ktime_get_boottime_seconds()
ktime_get_coarse_clocktai_ts64()
ktime_get_clocktai_seconds()

to fill in some of the missing pieces. I have missed only the
ktime_get_boottime_seconds() accessor in a few occasions in
the past, but it seems better to just provide all four together,
as there is very little cost to having them.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: y2038@lists.linaro.org
Cc: John Stultz <john.stultz@linaro.org>
Link: https://lkml.kernel.org/r/20180427134016.2525989-6-arnd@arndb.de

include/linux/timekeeping.h

@@ -137,18 +137,40 @@ extern u64 ktime_get_boot_fast_ns(void);
 extern u64 ktime_get_real_fast_ns(void);
 
 /*
- * timespec64 interfaces utilizing the ktime based ones
+ * timespec64/time64_t interfaces utilizing the ktime based ones
+ * for API completeness, these could be implemented more efficiently
+ * if needed.
  */
 static inline void ktime_get_boottime_ts64(struct timespec64 *ts)
 {
 	*ts = ktime_to_timespec64(ktime_get_boottime());
 }
 
+static inline void ktime_get_coarse_boottime_ts64(struct timespec64 *ts)
+{
+	*ts = ktime_to_timespec64(ktime_get_coarse_boottime());
+}
+
+static inline time64_t ktime_get_boottime_seconds(void)
+{
+	return ktime_divns(ktime_get_coarse_boottime(), NSEC_PER_SEC);
+}
+
 static inline void ktime_get_clocktai_ts64(struct timespec64 *ts)
 {
 	*ts = ktime_to_timespec64(ktime_get_clocktai());
 }
 
+static inline void ktime_get_coarse_clocktai_ts64(struct timespec64 *ts)
+{
+	*ts = ktime_to_timespec64(ktime_get_coarse_clocktai());
+}
+
+static inline time64_t ktime_get_clocktai_seconds(void)
+{
+	return ktime_divns(ktime_get_coarse_clocktai(), NSEC_PER_SEC);
+}
+
 /*
  * RTC specific
  */