On Wednesday 22 July 2009 12:17:59 Rupjyoti Sarmah wrote:
> Hi All,
>
> I am working on a PowerPC target. I want to change the CPU clock rate
> dynamically. Could you please suggest/point me to
>
> 1) the steps to do so ( I intend to execute a command from command
> line )
> 2) Necessary files/libraries that might be needed
>
> I would appreceiate your suggestions, I am using linux 2.6.30 kernel.
Find the corresponding PowerPC low-level cpufreq driver for your HW.
I am not familiar with PowerPC cpufreq drivers you should find them by
doing:
grep -r cpufreq_register_driver arch/.../
Make sure it loads successfully.
You then probably want to use the userspace governor:
modprobe cpufreq_userspace, or better compile it into the kernel
and additionally set:
CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE=y
then you do not need to do:
echo userspace >/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
Now you can use:
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
and
echo xy >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
Instead of accessing /sys/devices/system/cpu/cpu*/cpufreq
directly you should better use the cpufrequtils project/package
which already provides you most of above and more with simple command(s)
and param(s) (once you find a low-level driver serving your HW).
Thomas
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