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>
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 900f1b6..687dff4 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -182,7 +182,7 @@
*/
static void change_clocksource(void)
{
- struct clocksource *new;
+ struct clocksource *new, *old;
new = clocksource_get_next();
@@ -191,11 +191,16 @@
clocksource_forward_now();
- new->raw_time = clock->raw_time;
+ if (clocksource_enable(new))
+ return;
+ new->raw_time = clock->raw_time;
+ old = clock;
clock = new;
+ clocksource_disable(old);
+
clock->cycle_last = 0;
- clock->cycle_last = clocksource_read(new);
+ clock->cycle_last = clocksource_read(clock);
clock->error = 0;
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -292,6 +297,7 @@
ntp_init();
clock = clocksource_get_next();
+ clocksource_enable(clock);
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
clock->cycle_last = clocksource_read(clock);