Re: nokia 770 [was Re: community PM requirements/issues and PowerOP]

Pavel Machek
2006-12-14T14:56:10Z

> >But what sense does it make for a user,sysadmin or
> >application
> >to change voltage? If any of these want to save power,
> >they do so
> >by a) doing less work, and then b) lowering the clock
> >speed as this
> >is inherently tied to voltage.
>
> It makes sense to perform changing an operating point
> dynamically in
> userland.

In very special cases, yes.

> That said, voltage should be accessible from userland.

Why?

If few states differ in voltage but not frequency, the only
user-visible thing is different latency of enter/exit.

If you only have two voltages per frequency (as it was shown in
examples here)... just add 1Hz to make difference between the two.

...but I guess you should teach cpufreq's ondemand governor to deal
with different latencies for different voltages. Before that is done
and shown to have significant power-saving impact, userspace interface
debate is useless.
Pavel

--
Thanks for all the (sleeping) penguins.