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

Matthew Locke
2006-12-13T21:44:02Z

On Dec 13, 2006, at 1:32 PM, 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?

Example operating points were requested. Using the operating points
from DPM is fine for examples.

>
> I thought the question was specifically what N770 used.

Answered this in my other email.

>
>
>> 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.

Except that cpufreq doesn't really support voltage changes and N770
doesn't have the h/w to change voltage.

>
> ... that's in addition to the reduced power idle, which didn't seem to
> fit into the DPM framework in any obvious way.

Actually, automatically reducing power at idle is what DPM is all
about. In DPM an operating point is mapped to the idle state so when
the idle task is entered an operating point change is triggered. The
system can choose the best point for the idle task based on latency
requirements, length of idle when using dynamic ticks, etc.

>
> - Dave