timekeeping: Provide ktime_mono_to_any()

ktime based conversion function to map a monotonic time stamp to a
different CLOCK.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

2 files changed, 29 insertions, 0 deletions

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 3050a7d0a5a9..910a98ef2154 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -109,6 +109,7 @@ enum tk_offsets {
 extern ktime_t ktime_get(void);
 extern ktime_t ktime_get_with_offset(enum tk_offsets offs);
 extern ktime_t ktime_get_monotonic_offset(void);
+extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
 
 /**
  * ktime_get_real - get the real (wall-) time in ktime_t format
@@ -137,6 +138,14 @@ static inline ktime_t ktime_get_clocktai(void)
         return ktime_get_with_offset(TK_OFFS_TAI);
 }
 
+/**
+ * ktime_mono_to_real - Convert monotonic time to clock realtime
+ */
+static inline ktime_t ktime_mono_to_real(ktime_t mono)
+{
+        return ktime_mono_to_any(mono, TK_OFFS_REAL);
+}
+
 /*
  * RTC specific
  */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e99350319eec..032e77a54a79 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -451,6 +451,26 @@ ktime_t ktime_get_with_offset(enum tk_offsets offs)
 EXPORT_SYMBOL_GPL(ktime_get_with_offset);
 
 /**
+ * ktime_mono_to_any() - convert mononotic time to any other time
+ * @tmono:      time to convert.
+ * @offs:       which offset to use
+ */
+ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
+{
+        ktime_t *offset = offsets[offs];
+        unsigned long seq;
+        ktime_t tconv;
+
+        do {
+                seq = read_seqcount_begin(&tk_core.seq);
+                tconv = ktime_add(tmono, *offset);
+        } while (read_seqcount_retry(&tk_core.seq, seq));
+
+        return tconv;
+}
+EXPORT_SYMBOL_GPL(ktime_mono_to_any);
+
+/**
  * ktime_get_ts64 - get the monotonic clock in timespec64 format
  * @ts:         pointer to timespec variable
  *