linux-kernel - [79/80] clocksource: Fix bug with max

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Date:	Wed, 07 Dec 2011 08:07:39 -0800
From:	Greg KH <gregkh@...e.de>
To:	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Cc:	<torvalds@...ux-foundation.org>, <akpm@...ux-foundation.org>,
	<alan@...rguk.ukuu.org.uk>,
	"Yang Honggang (Joseph)" <eagle.rtlinux@...il.com>,
	John Stultz <john.stultz@...aro.org>
Subject: [79/80] clocksource: Fix bug with max_deferment margin calculation

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Yang Honggang (Joseph)" <eagle.rtlinux@...il.com>

commit b1f919664d04a8d0ba29cb76673c7ca3325a2006 upstream.

In order to leave a margin of 12.5% we should >> 3 not >> 5.

Signed-off-by: Yang Honggang (Joseph) <eagle.rtlinux@...il.com>
[jstultz: Modified commit subject]
Signed-off-by: John Stultz <john.stultz@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/time/clocksource.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -531,7 +531,7 @@ static u64 clocksource_max_deferment(str
 	 * note a margin of 12.5% is used because this can be computed with
 	 * a shift, versus say 10% which would require division.
 	 */
-	return max_nsecs - (max_nsecs >> 5);
+	return max_nsecs - (max_nsecs >> 3);
 }
 
 #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
@@ -653,7 +653,7 @@ void __clocksource_updatefreq_scale(stru
 	 * ~ 0.06ppm granularity for NTP. We apply the same 12.5%
 	 * margin as we do in clocksource_max_deferment()
 	 */
-	sec = (cs->mask - (cs->mask >> 5));
+	sec = (cs->mask - (cs->mask >> 3));
 	do_div(sec, freq);
 	do_div(sec, scale);
 	if (!sec)


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