From c7121843685de2bf7f3afd3ae1d6a146010bf1fc Mon Sep 17 00:00:00 2001
From: Magnus Damm <magnus.damm@gmail.com>
Date: Tue, 28 Jul 2009 14:09:55 -0700
Subject: [PATCH] clocksource: Save mult_orig in clocksource_disable()
To fix the common case where ->enable() does not set up
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@igel.co.jp>
Cc: johnstul@us.ibm.com
Cc: lethal@linux-sh.org
Cc: akpm@linux-foundation.org
LKML-Reference: <20090618152432.10136.9932.sendpatchset@rx1.opensource.se>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/clocksource.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index c56457c8334e..1219be4fb42e 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -293,7 +293,12 @@ static inline int clocksource_enable(struct clocksource *cs)
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 +314,13 @@ static inline int clocksource_enable(struct clocksource *cs)
*/
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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