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

["Eugeny S. Mints" <eugeny.mints@gmail.com>]

David Brownell wrote:
> On Wednesday 13 December 2006 1:03 pm, Pavel Machek wrote:
>> On Wed 2006-12-13 15:12:07, Eugeny S. Mints wrote:
>>> David Brownell wrote:
>>>> On Tuesday 19 September 2006 11:25 am, Pavel Machek wrote:
>>>>> Could you perhaps provide list of operating points for 770? It would
>>>>> help understanding a bit, I'd say.
>>>> If there was a followup here, I missed it ...
>>>>
>>>> ISTR that it doesn't use (formal) operating points, and that a lot of the
>>>> basic SOC power savings (vs powering off the display or wifi) come from a
>>>> different kind of mechanism entirely.  Namely, a combination of dynamic
>>>> tick with a modified system idle task, which enters one of the OMAP low
>>>> power modes during those long periods between clock ticks or other irqs.
>>>>
>>>> That's one of the standard power saving schemes used on OMAP1 platforms
>>>> with Linux.
>>> sample of reasonable operating points for OMAP1 platforms along with appropriate 
>>> patches may be found at http://dynamicpower.sourceforge.net/dpm-omap.html
> 
> That's the old DPM stuff not any of the newer proposals right?
> 
> I thought the question was specifically what N770 used.
> 
> 
>> Okay... so you have system with 4 different cpu speeds. That should be
>> simple enough to get running using cpufreq, no need for complex
>> operating points patches.
> 
> And OMAP1 does have cpufreq support.  I believe that if I checked it out
> I'd find that it's used on N770, as a good way to kick in low voltage
> operation modes.
> 
> ... that's in addition to the reduced power idle, which didn't seem to
> fit into the DPM framework in any obvious way.
It fits. Omitting some details DPM allows to map/stick operating point to tasks. 
Mapping one of OMAP low power mode operating point to idle task does the job.

Eugeny
> 
> - Dave
>