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authorMagnus Damm <damm@igel.co.jp>2009-04-21 12:24:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-21 13:41:47 -0700
commit4614e6adafa2c5e6c3a9c245af2807fa7bc5117a (patch)
treee4bb5eeaa252ede053abc6b3c4d15c4127ce7a32 /include/linux/clocksource.h
parent8e19608e8b5c001e4a66ce482edc474f05fb7355 (diff)
downloadlwn-4614e6adafa2c5e6c3a9c245af2807fa7bc5117a.tar.gz
lwn-4614e6adafa2c5e6c3a9c245af2807fa7bc5117a.zip
clocksource: add enable() and disable() callbacks
Add enable() and disable() callbacks for clocksources. This allows us to put unused clocksources in power save mode. The functions clocksource_enable() and clocksource_disable() wrap the callbacks and are inserted in the timekeeping code to enable before use and disable after switching to a new clocksource. Signed-off-by: Magnus Damm <damm@igel.co.jp> Acked-by: John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/clocksource.h')
-rw-r--r--include/linux/clocksource.h31
1 files changed, 31 insertions, 0 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0d96cde9ee5d..5a40d14daa9f 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -144,6 +144,8 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
* The ideal clocksource. A must-use where
* available.
* @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)
@@ -163,6 +165,8 @@ struct clocksource {
struct list_head list;
int rating;
cycle_t (*read)(struct clocksource *cs);
+ int (*enable)(struct clocksource *cs);
+ void (*disable)(struct clocksource *cs);
cycle_t mask;
u32 mult;
u32 mult_orig;
@@ -275,6 +279,33 @@ static inline cycle_t clocksource_read(struct clocksource *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);
+}
+
+/**
* cyc2ns - converts clocksource cycles to nanoseconds
* @cs: Pointer to clocksource
* @cycles: Cycles