Fwd: ACPI support in LinuxBIOS - moderator approval (fwd)

[Eric W. Biederman]

jarcher at pobox.com writes:

> I mentioned APM because it seemed the simplest.  Realisticaly you'd want to
> follow the LinuxBIOS approach and do minimal stuff at the BIOS level and move
> most of the information to a linux driver.  So really all the BIOS portion has
> to detect and support are the conditions where the CPU goes through reset.  This
> should only be the suspend to ram and the suspend to disk states.
> 
> So how about a new simple LinuxBIOS PM interface?

There are several pieces to this.

1) Telling operating systems what part it needs to play.
2) Switching to the suspend to RAM state.
3) Knowing in the BIOS we need to come out of suspend to RAM
   instead of doing a fresh initialization of the memory controller.

Thinking about Suspend to RAM I have some strange thoughts about setting
up hypertransport correctly.  I am wondering if a suspend to RAM would
be faster than a hard_reset?  Anyway...

On the LinuxBIOS side the communication can pretty much be accomplished
with a CMOS parameter I think.

As far as giving information to the running OS giving it the tables it
expects is not the worst way to go.  Most of the power management needs
to happen in the OS and in the drivers.   Ideally we would package the
ACPI table entries in the LinuxBIOS table as real tabular data (not
functions) and then convert them to real ACPI later.

The OS needs a little bit of help to do suspend to RAM but we should
keep it as minimal as possible.

Eric