PowerMac PMU programming

[Benjamin Herrenschmidt]

On Sun, 2012-06-10 at 09:29 -0400, Justin Hibbits wrote:
> Hello,
> 
> I'm working on various PMU bits for FreeBSD (I know, not related to
> Linux), but running into some problems, which the Linux crowd may be
> able to help with, as it's already solved for Linux.  I've managed to
> get it to sleep for performing the sleep operation and for the CPU speed
> switch on MPC7455-based machines, but it goes catatonic, not waking
> up.  I've installed the reset vector pointer at 0x0080, which both OS X
> and Linux do, and flush the caches, but no luck.  During development of
> the Linux driver was this ever encountered?  Any assistance would be
> greatly appreciated, I've been banging my head against this off and on
> for about 8 months now.
> 
> Thanks for any assistance.  I'm not subscribed to the list, so please
> keep my address in replies.

Yes it was :-) pretty much any bug even minor during that process will
cause just that :-)

One thing paulus did that helped us a lot initially was write a little
synchronous version of the PMU send command and use it to blink the PMU
LED very early on when resuming from sleep, which allows us to debug a
bit.

It takes quite a bit of work (see the code in radeonfb) to get the
graphics back, so most of the time you come back with nothing on screen.

If your machine is not a laptop, there are other possible
considerations, such as the need to restore the PCI-PCI bridge that
might be above the macio chip very early on, before you try to restore
macio itself (we don't do that in Linux at this stage).

Cheers,
Ben.