From 0c3749c41f5eee0da36bbf92b2793338b4d8574f Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 3 Feb 2006 21:51:41 +0100 Subject: [PATCH] x86_64: Calibrate APIC timer using PM timer On some broken motherboards (at least one NForce3 based AMD64 laptop) the PIT timer runs at a incorrect frequency. This patch adds a new option "apicpmtimer" that allows to use the APIC timer and calibrate it using the PMTimer. It requires the earlier patch that allows to run the main timer from the APIC. Specifying apicpmtimer implies apicmaintimer. The option defaults to off for now. I tested it on a few systems and the resulting APIC timer frequencies were usually a bit off, but always <1%, which should be tolerable. TBD figure out heuristic to enable this automatically on the affected systems TBD perhaps do it on all NForce3s or using DMI? Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- Documentation/x86_64/boot-options.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'Documentation') diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt index 654ea4fccff88..153740f460a6c 100644 --- a/Documentation/x86_64/boot-options.txt +++ b/Documentation/x86_64/boot-options.txt @@ -47,6 +47,11 @@ APICs noapicmaintimer Don't do time keeping using the APIC timer. Useful when this option was auto selected, but doesn't work. + apicpmtimer + Do APIC timer calibration using the pmtimer. Implies + apicmaintimer. Useful when your PIT timer is totally + broken. + Early Console syntax: earlyprintk=vga -- cgit 1.2.3-korg