Power management concept...

Nils Faerber nils.faerber at kernelconcepts.de
Thu Apr 19 17:16:51 CEST 2007

Harald Welte schrieb:
> On Thu, Apr 19, 2007 at 11:05:51AM +0200, Nils Faerber wrote:
>> Harald Welte schrieb:
>>> On Tue, Apr 17, 2007 at 04:58:49PM +0200, Nils Faerber wrote:
>>>> This is maybe slightly off-topic concerning hardware but anyway, what is
>>>> the power management concept planed for the NEO?
>>> Does 
>>> http://wiki.openmoko.org/wiki/Neo1973_Power_Management
>>> help you a bit?
>> A bit, yes, this describes what is possible, I guess.
>> What I was more curious about is how you actually intend to use it ;)
> well, I'd actaully rather spend time on the implementation than to
> preemptively talk about vapor that doesn't exist...

Probably the timing is not appropriate - you will be busy with other
things, I apologize...

> the wiki page explicitly distinguishes between PMU and CPU power states
> that 'theoretically' exist, and the 'system power states' that we have
> introduced for our actual use by system-level power management.

Ah, now I know what the 'system power states' are meant to be.

>> So, do you want to actually use slow_mode instead of any real sleep
>> modes with SDRAM in self refresh, correct?
> yes, that is already there. you can completely suspend to
> self-refreshing SDRAM and resume from that.  Even the P0 phonse can do
> that.

Yes, saw that. Though that the GSM modem seems to be quite confused
afterwards, i.e. I have to power it down, power on again and restart
gsmd to get it to work again (most of the times at least).

>> That would mean that if the phone is sitting idle in my pocket the CPU
>> will be put in slow mode as least power consuming mode, correct?
>> Off-mode will then really be off, like in power off.
> no, unfortuantely 'power-off' mode is how samsung calls their 'suspend
> to sdram' mode.  That's once again a reason for the above wiki page to
> use and define state names and to translate between the various vendor
> state names and human readable language.

So normal "idle" state of the phone will be, according to the wiki page,
the SYS_POWER_SLEEP which means CPU Power_off mode and thus comparably
high latency on wakeup.
Thanks, that's basically what I wanted to know.

  nils faerber

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