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| author | Roman Zippel <zippel@linux-m68k.org> | 2008-09-22 14:42:44 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2008-09-24 17:33:13 +0200 |
| commit | d40e944c25fb4642adb2a4c580a48218a9f3f824 (patch) | |
| tree | 9be7107440704a84d17f9dde12991915931c5279 /include/linux/timex.h | |
| parent | 5cd1c9c5cf30d4b33df3d3f74d8142f278d536b7 (diff) | |
| download | linux-d40e944c25fb4642adb2a4c580a48218a9f3f824.tar.gz linux-d40e944c25fb4642adb2a4c580a48218a9f3f824.tar.bz2 linux-d40e944c25fb4642adb2a4c580a48218a9f3f824.zip | |
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>
Diffstat (limited to 'include/linux/timex.h')
| -rw-r--r-- | include/linux/timex.h | 2 |
1 files changed, 1 insertions, 1 deletions
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) |