clocksource: Add __clocksource_updatefreq_hz/khz methods

To properly handle clocksources that change frequencies
at the clocksource->enable() point, this patch adds
a method that will update the clocksource's mult/shift and
max_idle_ns values.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1279068988-21864-12-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 35 insertions, 5 deletions

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 21677d99a161..c37b21ad5a3b 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -292,6 +292,8 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
  */
 extern int
 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
+extern void
+__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
 
 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 {
@@ -303,6 +305,15 @@ static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
         return __clocksource_register_scale(cs, 1000, khz);
 }
 
+static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
+{
+        __clocksource_updatefreq_scale(cs, 1, hz);
+}
+
+static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
+{
+        __clocksource_updatefreq_scale(cs, 1000, khz);
+}
 
 static inline void
 clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c543d21b4e54..c18d7efa1b4b 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -639,19 +639,18 @@ static void clocksource_enqueue(struct clocksource *cs)
 #define MAX_UPDATE_LENGTH 5 /* Seconds */
 
 /**
- * __clocksource_register_scale - Used to install new clocksources
+ * __clocksource_updatefreq_scale - Used update clocksource with new freq
  * @t:          clocksource to be registered
  * @scale:      Scale factor multiplied against freq to get clocksource hz
  * @freq:       clocksource frequency (cycles per second) divided by scale
  *
- * Returns -EBUSY if registration fails, zero otherwise.
+ * This should only be called from the clocksource->enable() method.
  *
  * This *SHOULD NOT* be called directly! Please use the
- * clocksource_register_hz() or clocksource_register_khz helper functions.
+ * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.
  */
-int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
+void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
 {
-
         /*
          * Ideally we want to use  some of the limits used in
          * clocksource_max_deferment, to provide a more informed
@@ -662,7 +661,27 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
                                       NSEC_PER_SEC/scale,
                                       MAX_UPDATE_LENGTH*scale);
         cs->max_idle_ns = clocksource_max_deferment(cs);
+}
+EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
+
+/**
+ * __clocksource_register_scale - Used to install new clocksources
+ * @t:          clocksource to be registered
+ * @scale:      Scale factor multiplied against freq to get clocksource hz
+ * @freq:       clocksource frequency (cycles per second) divided by scale
+ *
+ * Returns -EBUSY if registration fails, zero otherwise.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * clocksource_register_hz() or clocksource_register_khz helper functions.
+ */
+int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+
+        /* Intialize mult/shift and max_idle_ns */
+        __clocksource_updatefreq_scale(cs, scale, freq);
 
+        /* Add clocksource to the clcoksource list */
         mutex_lock(&clocksource_mutex);
         clocksource_enqueue(cs);
         clocksource_select();