Power management for ppc 85xx

[Chamorro, Marta]

Hi again, Kumar,

You said on your first reply that it was easy to get the core to nap, so
that sounds like a suitable first step for me.

Any pointers? Is there, for instance, any ppc implementation of power
management I could look at to see how's done?

Thanks,

Marta


-----Original Message-----
From: Kumar Gala [mailto:galak at kernel.crashing.org] 
Sent: 06 December 2006 21:51
To: Chamorro, Marta
Cc: linuxppc-dev at ozlabs.org; linuxppc-embedded at ozlabs.org
Subject: Re: Power management for ppc 85xx


On Dec 6, 2006, at 3:06 PM, Chamorro, Marta wrote:

> Hi there!
>
>
>
> Hope someone out there can give me some pointers here. I've got a  
> 2.6.18 kernel on a ppc 8555, which I configured to enable power  
> management (CONFIG_PM=y). After doing that, the file /sys/power/ 
> state appears on my file system. If I cat the file I get "standby  
> mem" (without the quotes), but if I try to write to it (to change  
> the state) I get an EPERM. I assume it is because I have no code  
> that implements any power save mode changes, only the interface to  
> change them. Am I wrong? How can I tell for sure? (the file is  
> writable, so it is not a problem with writing permissions)
I can pretty much say that there isn't any code that does pwr mgmt  
for 85xx.  I'm not sure what exactly your issue is, but there  
definitely isn't any code.
> So the question is (if I am right) where do I get the code from? I  
> am hoping someone has implemented power save for that processor  
> already, but I just don't know where to start looking for that  
> code. Can someone help?
Getting the core to nap is easy enough, doing proper power savings  
for the full SoC maybe more challenging.

What exact behavior are you looking for?  Something like suspend/ 
resume or just idle power savings?

- k