From: Jack Steiner Date: Thu, 11 Jan 2007 00:52:44 +0000 (+0100) Subject: [PATCH] x86-64: - Ignore long SMI interrupts in clock calibration X-Git-Tag: v2.6.20-rc5~24^2~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ed5316d4457b35c7b4942af028d6b878174264f7;p=pandora-kernel.git [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 Signed-off-by: Andi Kleen arch/x86_64/kernel/time.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) --- Reading git-diff-tree failed