2 files changed, 22 insertions, 0 deletions

diff --git a/include/linux/time.h b/include/linux/time.h
index 242f62499bb7..ea16c1a01d51 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -113,6 +113,21 @@ struct timespec current_kernel_time(void);
 #define CURRENT_TIME            (current_kernel_time())
 #define CURRENT_TIME_SEC        ((struct timespec) { get_seconds(), 0 })
 
+/* Some architectures do not supply their own clocksource.
+ * This is mainly the case in architectures that get their
+ * inter-tick times by reading the counter on their interval
+ * timer. Since these timers wrap every tick, they're not really
+ * useful as clocksources. Wrapping them to act like one is possible
+ * but not very efficient. So we provide a callout these arches
+ * can implement for use with the jiffies clocksource to provide
+ * finer then tick granular time.
+ */
+#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
+extern u32 arch_gettimeoffset(void);
+#else
+static inline u32 arch_gettimeoffset(void) { return 0; }
+#endif
+
 extern void do_gettimeofday(struct timeval *tv);
 extern int do_settimeofday(struct timespec *tv);
 extern int do_sys_settimeofday(struct timespec *tv, struct timezone *tz);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 687dff49f6e7..e97c50f8458b 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -77,6 +77,10 @@ static void clocksource_forward_now(void)
         clock->cycle_last = cycle_now;
 
         nsec = cyc2ns(clock, cycle_delta);
+
+        /* If arch requires, add in gettimeoffset() */
+        nsec += arch_gettimeoffset();
+
         timespec_add_ns(&xtime, nsec);
 
         nsec = ((s64)cycle_delta * clock->mult_orig) >> clock->shift;
@@ -111,6 +115,9 @@ void getnstimeofday(struct timespec *ts)
                 /* convert to nanoseconds: */
                 nsecs = cyc2ns(clock, cycle_delta);
 
+                /* If arch requires, add in gettimeoffset() */
+                nsecs += arch_gettimeoffset();
+
         } while (read_seqretry(&xtime_lock, seq));
 
         timespec_add_ns(ts, nsecs);