Re: Totally broken PCI PM calls

[Nigel Cunningham <ncunningham@linuxmail.org>]

Hi.

On Tue, 2004-10-12 at 21:27, Benjamin Herrenschmidt wrote:
> > > In the first case, it makes even sense to keep the driver operating
> > > while the device is D1, the driver would then just wake the device on an
> > > incoming request (provided this is allowed by the policy). In the later
> > > case, the driver state is the only thing that matters.
> > 
> > Not quite - you have to be able to get the device into a matching state
> > at resume time. Probably not a problem in most cases, I realise, but
> > thought it was worth a mention.
> 
> Wait, I'm not talking about swsusp here, that's exactly my distinction
> between driver state and device state :) Only system suspend like swsusp
> and suspend-to-ram require a completely coherent and frozen memory
> "image".

Oh ok. I thought suspend was one application of what you were talking
about (not necessarily the only one, but one...)

> All sorts of dynamic PM, including system-wide "idle" can deal with
> scenarios where the driver can stay functional and decide by itself to
> wake up the device upon incoming requests.
> 
> > [...]
> > 
> > > Yup, with the exception that it becomes hell when those devices are
> > > anywhere on the VM path... which makes userspace policy unuseable for
> > > system suspend.
> > 
> > A device on the VM path? I don't follow here. Can I have a hand please?
> 
> Any block device basically, I don't even want to think about the issues
> between NFS & suspend :)

> That is anything that userspace potentially requires to operate (device on
> the path to an mmap'd file, swap, whatever)...

Ah.. I'm with you now. The 'VM path' was too abstract for me at 9:30pm
:>.

Nigel
-- 
Nigel Cunningham
Pastoral Worker
Christian Reformed Church of Tuggeranong
PO Box 1004, Tuggeranong, ACT 2901

Many today claim to be tolerant. True tolerance, however, can cope with others
being intolerant.