From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Timer interrupts after CPU speed change Date: Wed, 26 Mar 2003 19:06:52 +0000 Sender: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Message-ID: <20030326190652.GA12645@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Errors-To: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: To: acpi-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-acpi@vger.kernel.org For reasons that (as yet) aren't entirely clear to me, suspending my laptop to S3 when it's on battery results in it failing to resume correctly (hard drive LED comes on and stays on - it's probably a DMA issue or something similarly entertaining, but I've got no console once it resumes so it's hard to tell). However, booting on battery, connecting it to AC and then suspending allows a resume to work. The problem is as follows: When booting on battery, the CPU runs at 133MHz. As far as I've been able to tell, this machine doesn't support Speedstep (it's a mobile PIII 500, and the Intel information I've found seems to suggest that Speedstep only appeared with the 600s) and from poking various registers it seems to accomplish this by using throttling (if I force those registers to the values that change when changing between AC and battery, the selected throttling value in /proc/acpi/ changes). Attaching power results in the processor speeding up again (and, though I haven't checked, I /think/ that just starting ACPI when on battery actually results in it running at full speed). If I now suspend, carry my laptop around for a while, attach it to power and resume, the system timer starts firing at 4096Hz rather than 1024Hz with fairly predictable consequences. /proc/cpuinfo continues to say that the processor is 133MHz, though it's now running happily at 500 (and was running at 500 before being suspended as well). Is there any obvious fix for this? Thanks, -- Matthew Garrett | mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org ------------------------------------------------------- This SF.net email is sponsored by: The Definitive IT and Networking Event. Be There! NetWorld+Interop Las Vegas 2003 -- Register today! http://ads.sourceforge.net/cgi-bin/redirect.pl?keyn0001en