Power management concept...

Nils Faerber nils.faerber at kernelconcepts.de
Tue Apr 24 13:29:09 CEST 2007

Harald Welte schrieb:
> On Fri, Apr 20, 2007 at 12:53:10PM +0200, Nils Faerber wrote:
>> Harald Welte schrieb:
>>> On Thu, Apr 19, 2007 at 05:16:51PM +0200, Nils Faerber wrote:
>>>> 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).
>>> Note that none of the phones ever shipped has a GSM firmware installed
>>> that supports proper suspend/resume.  We have something like a six to
>>> eight week turn around time when reporting an issue to Ti until we get a
>>> fix :(
>> If the suspend mode (i.e. power-off mode in Samsung terms, i.e. self
>> refresh SDRAM and wake-up configured) is the mode that will be used as
>> state 90% of the run-time (most of the time the phone will be waiting
>> for events in a pocket) couldn't we simply leave the modem running in
>> run-state and leave the suspend/resume feature as a later enhancement?
> the suspend mode (power-off mode with sdram self-refresh) is exactly the
> suspend/resume that we're talking about.
> I don't really understand what you want, sorry.  

In other words I wanted to know if the idle mode would be in use instead
of the power-off mode. That would make the device more responsive
(wake-up latency) and is exactly what is also used by other devices like
the Nokia 770/N800 and obviously working well.

> What you describe seems to be what is in place right now.

That is correct and I am sorry for the confusion I might have caused.

Will the slow mode also be supported and how will it be entered?
Automatically or by userspace intervention? Or is it already used in
kernel idle state?

You mention it as an option for SYS_POWER_ON_SCRSAVE but not how to
actually put the device there. "Power-off" is easy, simply

	echo mem > /sys/power/state

Personally I would be much more interested in slow-mode than in
suspend/power-off. As I described it would allow (slow) applications
running all the time without much power consumption. This would be a
very interesting feature.

Anyway concentrating on the more pressuring things is of course more
important so I will shut up now ;)

  nils faerber

kernel concepts GbR        Tel: +49-271-771091-12
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