Power management for ppc 85xx

[Chamorro, Marta]

Hi Clemens,

> 
> Hello, Kumar, Hi, Marta!
> 
> >> Glad I managed to make sense. I checked the hardware spec on the
board
> >> and it looks like we're using everything, apart from the SEC and
maybe
> >> the stand-alone I2C (I think we're just using the one within the
CMP).
> >> By the way, I made a mistake and the actual processor on the board
is
> >> the cut-down 8541, not the 8555. My apologies for that.
> >>
> >> This morning I added some printks and confirmed that there is no
code
> >> behind pm_ops, so my question remains: is there some code out there
> >> that
> >> I can use? (hope so, otherwise I'm doomed...)
> >
> > I'm sorry to say you're doomed.  I don't believe anyone's spent any
> > time trying to do pwr mgmt on 85xx.
> 
> I am working with the MPC8540 in a mobile product and some
> power saving would be fine to use. But I haven't seen any
> power management code for that thingy in the kernels at all.
> So, there is some work left there. Maybe I will have
> a closer look in the future.
> 
> According to some tests of a board manufacturer, the cpu
> doesn't power down very much, when you stop some peripherals
> or send the core to nap. But I wasn't able to confirm that yet.

We're estimating 2.5 watts saving on doze mode, in case that helps.
That's for a 8545 @ 800MHz

> 
> Best greets,
> 
> Clemens Koller
> _______________________________

Bfn,

Marta Chamorro