[maemo-developers] Internet Tablet Power Management presentation from linux-pm summit 2007

From: Frantisek Dufka dufkaf at seznam.cz
Date: Wed Jul 11 11:08:48 EEST 2007
Igor Stoppa wrote:
> Hi,
> this is the presentation we gave last week in Ottawa at the pm summit.
> It is the first step in improving our communication process with the
> community and give a preview of what we are working on.
> http://maemo.org/midcom-permalink-0c828d202f2011dc9945e502835830f130f1
> It contains a brief overview of what is already shipping in the 770 and
> the n800, but the main focus is about our work in progress.
> Comments and questions are welcomed.

Thanks Igor, it is quite interesting. Maybe there is a bug on page 15 
with DSP frequency for OP 0, shouldn't the 133 be 233 or 333 (unless you 
need to slow it down because of speeding up the arm core to meet some 
power requirement)? Does it mean the arm core in current N800 can run at 

As for dynamic voltage and frequency scaling did I understood it 
correctly that even if lower voltage means considerable saving (even if 
task runs longer) it is almost not worth the hassle due to other issues 
(latency of voltage/frequency change, static power consumption of other 
parts, hard prediction of future)? Or how big savings do you expect 
overall from voltage/frequency scaling when the device is mostly idle 
(i.e being mostly waken up by inefficient system or apps waiting for 
something and not hogging the CPU). Or maybe the question is how 
efficient is the system currently, is there something like 
http://www.linuxpowertop.org/ for omap to see what can be improved or 
what cannot and could benefit from lower frequency/voltage?

Do you plan to have user selectable power/speed profiles to let people 
choose whether they want slower system or shorter battery life? Or do 
you suppose there will be good enough cpufreq governor so it is not 
needed. Or do you consider some API so apps can suggest how fast system 
they want (i.e. media players, games, emulators vs book readers)?


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