1 files changed, 34 insertions, 3 deletions

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 573819ef4cc..5a40d14daa9 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -143,7 +143,9 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
  *                      400-499: Perfect
  *                              The ideal clocksource. A must-use where
  *                              available.
- * @read:               returns a cycle value
+ * @read:               returns a cycle value, passes clocksource as argument
+ * @enable:             optional function to enable the clocksource
+ * @disable:            optional function to disable the clocksource
  * @mask:               bitmask for two's complement
  *                      subtraction of non 64 bit counters
  * @mult:               cycle to nanosecond multiplier (adjusted by NTP)
@@ -162,7 +164,9 @@ struct clocksource {
         char *name;
         struct list_head list;
         int rating;
-        cycle_t (*read)(void);
+        cycle_t (*read)(struct clocksource *cs);
+        int (*enable)(struct clocksource *cs);
+        void (*disable)(struct clocksource *cs);
         cycle_t mask;
         u32 mult;
         u32 mult_orig;
@@ -271,7 +275,34 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
  */
 static inline cycle_t clocksource_read(struct clocksource *cs)
 {
-        return cs->read();
+        return cs->read(cs);
+}
+
+/**
+ * clocksource_enable: - enable clocksource
+ * @cs:         pointer to clocksource
+ *
+ * Enables the specified clocksource. The clocksource callback
+ * function should start up the hardware and setup mult and field
+ * members of struct clocksource to reflect hardware capabilities.
+ */
+static inline int clocksource_enable(struct clocksource *cs)
+{
+        return cs->enable ? cs->enable(cs) : 0;
+}
+
+/**
+ * clocksource_disable: - disable clocksource
+ * @cs:         pointer to clocksource
+ *
+ * Disables the specified clocksource. The clocksource callback
+ * function should power down the now unused hardware block to
+ * save power.
+ */
+static inline void clocksource_disable(struct clocksource *cs)
+{
+        if (cs->disable)
+                cs->disable(cs);
 }
 
 /**