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| author | Kasper Pedersen <kkp2010@kasperkp.dk> | 2010-10-20 15:55:15 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-06-23 15:24:09 -0700 |
| commit | a6d553ac64a6b3dc267eebccca446fd32d2e5e73 (patch) | |
| tree | 3781fb9552f6deaae61cd762fff4c53b6ccc6afa /drivers/net/wireless/iwlwifi/iwl-5000.c | |
| parent | 652c98bac315a2253628885f05cfd5f30b553ae5 (diff) | |
time: Compensate for rounding on odd-frequency clocksources
commit a386b5af8edda1c742ce9f77891e112eefffc005 upstream.
When the clocksource is not a multiple of HZ, the clock will be off. For
acpi_pm, HZ=1000 the error is 127.111 ppm:
The rounding of cycle_interval ends up generating a false error term in
ntp_error accumulation since xtime_interval is not exactly 1/HZ. So, we
subtract out the error caused by the rounding.
This has been visible since 2.6.32-rc2
commit a092ff0f90cae22b2ac8028ecd2c6f6c1a9e4601
time: Implement logarithmic time accumulation
That commit raised NTP_INTERVAL_FREQ and exposed the rounding error.
testing tool: http://n1.taur.dk/permanent/testpmt.c
Also tested with ntpd and a frequency counter.
Signed-off-by: Kasper Pedersen <kkp2010@kasperkp.dk>
Acked-by: john stultz <johnstul@us.ibm.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Will Tisdale <willtisdale@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/net/wireless/iwlwifi/iwl-5000.c')
0 files changed, 0 insertions, 0 deletions