From: Matthew Garrett <mjg59@sr...> - 2003-03-26 19:08:01
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?
Matthew Garrett | mjg59@...
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