[ltp] Thinkpad R40 2722: various CPUFREQ troubles

Sebastian Kapfer linux-thinkpad@linux-thinkpad.org
Thu, 11 Dec 2003 14:31:16 +0100

Hello Thinkpad users,

My Thinkpad R40 (2722-GDG) works quite well under Linux, except for a
few obstacles. It would be nice if someone could shed a bit of light on
the issue. I have found a mail with a single question on this list, but
without a real solution. :-(

* I Can't clock the machine at 1500 MHz when disconnected from external
power. I know IBM wants to conserve battery power here. BUT I DON'T
CARE. A useless (slow) system is worse than one running two hours less.
Does this depend on BIOS settings? I think I tried everything possible,
but never got past 600 MHz.

* The system time runs slow. Order of magnitude is about 5 minutes slow
per hour of operation. This doesn't seem to occur when it is turned off.
I have to ntpdate several times a day. :-(  CPU frequency doesn't seem
to have any influence. Time is lost at about the same speed no matter if
1500 or 150 MHz. Google says ACPI will fix this (and it does), but with
ACPI the battery status doesn't work any more.

* Strange message in the syslog (appears once, some minutes after

| Losing too many ticks!
| TSC cannot be used as a timesource. (Are you running with SpeedStep?)
| Falling back to a sane timesource.

The answer to that question is probably "yes". The fallback timesource
obviously isn't more sane either, because it's still wrong :-(

After hours of googling, I found out that there's a kernel parameter
which controls the default timesource. Available options are "pit",
"tsc" and "cyclone".

cyclone isn't accepted by the kernel at all; tsc is the default anyway,
and when booted with clock=pit, CPUFREQ fails to detect a CPU. So I'm
not sure what to do to get rid of this message.

Summary of the system configuration:

Pentium M CPU, Linux 2.6-test9 kernel with the CPUFREQ stuff, APM mode,
acpi=off (you know, the battery).

BIOS settings: CPU frequency is set to "fixed max". (But still the CPU
runs at 600 instead of 1500.)

Enabling or disabling SpeedStep in the BIOS doesn't make any difference
whatsoever. CPUFREQ happily changes frequency in both modes, the system
time is slow in both.

Please help!

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