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| author | john stultz <johnstul@us.ibm.com> | 2008-02-10 10:48:03 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2008-02-10 10:48:03 +0100 |
| commit | e13a2e61dd5152f5499d2003470acf9c838eab84 (patch) | |
| tree | 4846b2ea392773f7a92d31334295d7aadbafd83e /include/linux | |
| parent | 25f666300625d894ebe04bac2b4b3aadb907c861 (diff) | |
| download | linux-e13a2e61dd5152f5499d2003470acf9c838eab84.tar.gz linux-e13a2e61dd5152f5499d2003470acf9c838eab84.tar.bz2 linux-e13a2e61dd5152f5499d2003470acf9c838eab84.zip | |
ntp: correct inconsistent interval/tick_length usage
clocksource initialization and error accumulation. This corrects a 280ppm
drift seen on some systems using acpi_pm, and affects other clocksources as
well (likely to a lesser degree).
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/timex.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/include/linux/timex.h b/include/linux/timex.h index 8ea3e71ba7fa..c3f374786a43 100644 --- a/include/linux/timex.h +++ b/include/linux/timex.h @@ -232,7 +232,14 @@ static inline int ntp_synced(void) #else #define NTP_INTERVAL_FREQ (HZ) #endif -#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ) + +#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE) +#define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / \ + (s64)CLOCK_TICK_RATE) + +/* Because using NSEC_PER_SEC would be too easy */ +#define NTP_INTERVAL_LENGTH ((((s64)TICK_USEC * NSEC_PER_USEC * USER_HZ) + \ + CLOCK_TICK_ADJUST) / NTP_INTERVAL_FREQ) /* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */ extern u64 current_tick_length(void); |