RE: Power management for ppc 85xx

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@kernel.crashing.org]=20
Sent: 06 December 2006 21:51
To: Chamorro, Marta
Cc: linuxppc-dev@ozlabs.org; linuxppc-embedded@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 =20
2.6.18 kernel on a ppc 8555, which I configured to enable power =20
management (CONFIG_PM=3Dy). After doing that, the file /sys/power/=20
state appears on my file system. If I cat the file I get "standby =20
mem" (without the quotes), but if I try to write to it (to change =20
the state) I get an EPERM. I assume it is because I have no code =20
that implements any power save mode changes, only the interface to =20
change them. Am I wrong? How can I tell for sure? (the file is =20
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 =20
for 85xx.  I'm not sure what exactly your issue is, but there =20
definitely isn't any code.

So the question is (if I am right) where do I get the code from? I =20
am hoping someone has implemented power save for that processor =20
already, but I just don't know where to start looking for that =20
code. Can someone help?

Getting the core to nap is easy enough, doing proper power savings =20
for the full SoC maybe more challenging.

What exact behavior are you looking for?  Something like suspend/=20
resume or just idle power savings?

- k