[PATCH 0/9] Experimental S3C2410A cpufreq driver

Cesar Eduardo Barros cesarb at cesarb.net
Wed Feb 13 11:34:29 CET 2008

Werner Almesberger escreveu:
> Did you measure what power saving all this yields in the end ? I've
> always been wondering if cpufreq will actually make a big difference
> on our devices, particularly on GTA02, where we run at a more
> power-efficient speed already by default.

No, I didn't try to measure anything so far. In fact, I'm also wondering 
how much of a difference it will make.

My plan is to use parts of what has to be done to make suspend work and 
combine it with cpufreq so the CPU can be always running but in a very 
low clock speed. For instance, with the cpufreq code so far in the 
drivers, you have to close the serial ports (after setting up the modem 
the same way you would do for a suspend) and turn off the screen 
(currently not possible; the code in the kernel just blanks it) before 
you can use the slow clock frequencies. Using them should save a lot of 
power with a faster wakeup than suspend (and as a bonus the userspace 
keeps running, although somewhat slowly).

Cesar Eduardo Barros
cesarb at cesarb.net
cesar.barros at gmail.com

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