linux-kernel - Re: cpufreq doesn't seem to work in Intel Q9300

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Message-ID: <48958901.06a0100a.35d6.2df9@mx.google.com>
Date:	Sun, 03 Aug 2008 11:31:27 +0100
From:	none <aj504@...dent.cs.york.ac.uk>
To:	S K <nospamnoham@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: cpufreq doesn't seem to work in Intel Q9300

S K wrote:
> Hi,
> 
>   I have an Intel Core 2 Quad and running kernel
> 2.6.25.11-97.fc9.i686. cpufreq doesn't seem to work. The cpufreq
> scaling monitor in Gnome says CPU Freq scaling is not supported in my
> CPU. The CPU can run at 2.0 and 2.5 GHz but mine always runs at 2.5
> GHz in Linux.
> 
> So I checked  /sys and there is no cpufreq dir in /sys/...
> 
> # ls /sys/devices/system/cpu/
> cpu0  cpu1  cpu2  cpu3  cpuidle  sched_mc_power_savings
> # ls /sys/devices/system/cpu/cpuidle/
> current_driver  current_governor_ro
> 
> I have no clue what cpuidle directory is for.
> 
> I added cpufreq.debug=7 in kernel boot params and saw the following in
> the dmesg:
> 
> speedstep-smi: No supported Intel CPU detected.
> cpufreq-core: CPU 0: _PPC is 0 - frequency not limited
> cpufreq-core: CPU 3: _PPC is 0 - frequency not limited
> cpufreq-core: CPU 1: _PPC is 0 - frequency not limited
> cpufreq-core: CPU 2: _PPC is 0 - frequency not limited
> cpuidle: using governor ladder
> cpuidle: using governor menu
> 
> I looked at arch/x86/kernel/cpu/cpufreq/speedstep-smi.c and it seems
> to detect only Pentium IIIs.
> 
> Anyone know what files have the cpufreq code for Intel Core 2?
> Does cpufreq support Intel Core 2 Quads? Especially the Q9300? If not,
> anything I can do to help?

I have an Intel Core 2 Duo and it uses the ACPI cpufreq driver; your
Quad should do the same.  So this is likely an ACPI/BIOS issue.

If you ask ACPI people they will ask you to post the output of acpidump.
Also you should probably check if you have a BIOS option that needs to be
enabled for this to work.

BTW, cpuidle is something quite different, it is about how to save power 
when CPU is doing nothing (i.e. idle :-).  Cpu frequency scaling is how to
save power when CPU is working (but doesn't need to run flat out).

Alan
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