[PATCH] clocksource: save mult_orig in clocksource_disable()

From: Magnus Damm
Date: Thu Jun 18 2009 - 11:28:20 EST


From: Magnus Damm <damm@xxxxxxxxxx>

Save clocksource mult_orig in clocksource_disable().

To fix the common case where ->enable() does not setup
mult, make sure mult_orig is saved in mult on disable.

Also add comments to explain why we do this.

Signed-off-by: Magnus Damm <damm@xxxxxxxxxx>
---

include/linux/clocksource.h | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

--- 0001/include/linux/clocksource.h
+++ work/include/linux/clocksource.h 2009-06-19 00:12:16.000000000 +0900
@@ -293,7 +293,11 @@ static inline int clocksource_enable(str
if (cs->enable)
ret = cs->enable(cs);

- /* save mult_orig on enable */
+ /* The frequency may have changed while the clocksource
+ * was disabled. If so the code in ->enable() must update
+ * the mult value to reflect the new frequency. Make sure
+ * mult_orig follows this change.
+ */
cs->mult_orig = cs->mult;

return ret;
@@ -309,6 +313,12 @@ static inline int clocksource_enable(str
*/
static inline void clocksource_disable(struct clocksource *cs)
{
+ /* Save mult_orig in mult so clocksource_enable() can
+ * restore the value regardless if ->enable() updates
+ * the value of mult or not.
+ */
+ cs->mult = cs->mult_orig;
+
if (cs->disable)
cs->disable(cs);
}
--
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