P-state setting suddenly disappeared, what gives?

[Adrian Chadd]

Hi all,

I have this Lenovo T400 that I've been doing FreeBSD development on for a while.

It has a P8700 in it:

CPU: Intel(R) Core(TM)2 Duo CPU     P8700  @ 2.53GHz (2527.07-MHz 686-class CPU)

Now, up until yesterday, ACPI exported the required twiddles to enter
various different P-states.

However, as of sometime yesterday, it stopped being able to do so.

sysctl dev.cpu.0.freq returns nothing. Setting it to something retuns
"device not configured." The frequency list (ie, the P-state list) is
still fine.

I had to load cpufreq.ko to get the enhanced speedstep stuff to show
up, but (a) it doesn't support this CPU (and it seems to have stopped
growing EST bits after Pentium M CPUs..) and (b) setting the frequency
using it versus P-state settings doesn't save as much power.

I'd like to try and debug why the heck this is.

The laptop still works fine, things are just not as "nice" as they once were.

Any ideas? Any suggestions on where to start debugging this?

Thanks!



-adrian