[PATCH] x86-64: - Ignore long SMI interrupts in clock calibration
Ensure that no SMI interrupts occur between the read of the HPET & TSC
in the clock calibration loop.
I noticed that a 2.66GHz system incorrectly detected the processor
clock speed about 1/7 of the time:
time.c: Detected 2660.005 MHz processor. (most of the time)
time.c: Detected 2988.203 MHz processor. (sometime)
The problem is caused by an SMI interrupt occuring in hpet_calibrate_tsc()
between the read of the HPET & TSC. Prior to switching the BIOS into
ACPI mode, it appears that every 27msec an SMI interrupt occurs. The
SMI interrupt takes 4.8 msec to process.
Note: On my test system, TICK_MIN had to be >380. I picked 5000
to minimize risk of having a value that is too small for other
platforms.
Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andi Kleen <ak@suse.de>
arch/x86_64/kernel/time.c | 25 +++++++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)
1 file changed