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[PATCH] x86_64: Fix drift with HPET timer enabled

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If the HPET timer is enabled, the clock can drift by ~3 seconds a day.
This is due to the HPET timer not being initialized with the correct
setting (still using PIT count).

If HZ changes, this drift can become even more pronounced.

HPET patch initializes tick_nsec with correct tick_nsec settings for
HPET timer.

Vojtech comments:

  "It's not entirely correct (it assumes the HPET ticks totally
   exactly), but it's significantly better than assuming the PIT error
   there."

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jordan Hargrave
2006-04-07 19:50:18 +02:00
committed by Linus Torvalds
parent 49c93e84d8
commit b20367a6c2
5 changed files with 12 additions and 1 deletions
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2
kernel/timer.c
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@@ -1455,7 +1455,7 @@ static void time_interpolator_update(long delta_nsec)
*/
if (jiffies % INTERPOLATOR_ADJUST == 0)
{
if (time_interpolator->skips == 0 && time_interpolator->offset > TICK_NSEC)
if (time_interpolator->skips == 0 && time_interpolator->offset > tick_nsec)
time_interpolator->nsec_per_cyc--;
if (time_interpolator->ns_skipped > INTERPOLATOR_MAX_SKIP && time_interpolator->offset == 0)
time_interpolator->nsec_per_cyc++;