From d40e944c25fb4642adb2a4c580a48218a9f3f824 Mon Sep 17 00:00:00 2001
From: Roman Zippel <zippel@linux-m68k.org>
Date: Mon, 22 Sep 2008 14:42:44 -0700
Subject: ntp: improve adjtimex frequency rounding

Change PPM_SCALE_INV_SHIFT so that it doesn't throw away any input bits
(19 is the amount of the factor 2 in PPM_SCALE), the output frequency
can then be calculated back to its input value, as the inverse divide
produce a slightly larger value, which is then correctly rounded by the
final shift.

Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/timex.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'include/linux/timex.h')

diff --git a/include/linux/timex.h b/include/linux/timex.h
index c00bcdd3ae42..9007313b5b71 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -82,7 +82,7 @@
  */
 #define SHIFT_USEC 16		/* frequency offset scale (shift) */
 #define PPM_SCALE (NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
-#define PPM_SCALE_INV_SHIFT 20
+#define PPM_SCALE_INV_SHIFT 19
 #define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
 		       PPM_SCALE + 1)
 
-- 
cgit v1.2.3