Re: ACPI: _PTS ordering needs fixing for pre ACPI 3.0 systems (was: Re: x86: Increase PCIBIOS_MIN_IO to 0x1500 to fix nForce 4 suspend-to-RAM)

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Tuesday, 25 of December 2007, Rafael J. Wysocki wrote:
> On Tuesday, 25 of December 2007, Carlos Corbacho wrote:
> > Adding Linux-ACPI to CC.
> > 
> > On Tuesday 25 December 2007 00:03:25 Carlos Corbacho wrote:
> > > According to the earlier versions of the ACPI spec, Linux is doing the
> > > wrong thing - we should call _PTS() before we start powerding down devices,
> > > or notifying device drivers to start suspending.
> > >
> > > So, my limited understanding of what we currently do for ACPI
> > > suspend-to-RAM is:
> > >
> > > 1) Freeze processes/ devices
> > > 2) Put all devices into low power mode
> > > 3) Execute _PTS()
> > > 4) Suspend system
> > >
> > > So the problem is - our current suspend order is fine for ACPI 3.0 and
> > > above, but for pre-3.0 systems, this violates the older specs, where 2) and
> > > 3) should be reversed.
> > 
> > The following is a hack to illustrate what I'm getting at (this is
> > tested on x86-64) (it's a hack since it does all the ACPI prepare bits
> > during set_target() for the pre ACPI 3.0 systems, rather than prepare() -
> > whether this can be cleaned up to move out just the _PTS() call, I don't
> > know).
> > 
> > It abuses suspend_ops->set_target(), but was the easiest way to quickly
> > demonstrate this (since the kerneldoc for set_target() says it will always
> > be executed before we suspend the devices).
> 
> Please, don't do that.

OK, sorry, the approach is generally reasonable, IMO, but it needs to be a bit
more fine grained.

I'll try to prepare some patches along these lines soon.

Thanks,
Rafael