[linux-pm] PM models

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On Mon, 2004-11-01 at 23:45 +0100, Pavel Machek wrote:
> Hi!
> 
> > Anyway, I think what we have defined so far seem to be good enough to
> > start the actual move. The only thing I'd like you to judge is wether we
> > keep the original PM message semantics we discussed, or we move the
> > freeze semantic to a separate flag as discussed in another message so
> > that we have some kind of generic way of triggering drivers local PM...
> 
> Actually it seems like an implementation detail to me... but I'd vote
> for separate flags. Distinction between "IDLE" and "SUSPEND" seems
> quite unclear to me.
> 
> OTOH... there's preparation for shutdown, which does not fit here too
> much, and preparation for apm sleep, which does not fit, either:
> 
> For shutdown, power state is not interesting, and you do not even need
> to freeze, but you'd better spin down the disks, or you loose your
> data.

If you don't freeze, a stal request may spin back up. Also, shutdown is
used for kexec as well, which absolutely need DMA off, that is freeze
semantics.

I suggest we define a shutdown message too. By default, busses would
call shutdown if it exist, if not, pass suspend with the shutdown
message. Looks ok ?

> For apm suspend... noone knows whats really required. Theoretically,
> neither freeze nor powersaving is needed.

Freeze would be a good thing tho. There are interesting "races" with APM
suspend that would be fixed... Also, saving/restoring device states
since APM tend to fail restore some stuffs here or there.

Ben.




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