linux-kernel - Re: PCI PM: Restore standard config registers of all devices early

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Date:	Tue, 3 Feb 2009 22:57:53 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Andreas Schwab <schwab@...e.de>, Len Brown <lenb@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: PCI PM: Restore standard config registers of all devices early

On Tuesday 03 February 2009, Linus Torvalds wrote:
> 
> On Tue, 3 Feb 2009, Rafael J. Wysocki wrote:
> > 
> > As I said, I tend to prefer the "loop of disable_irq()" approach, because it
> > would allow us to preserve the current ordering of ACPI operations.  Namely,
> > if we do:
> > 
> > suspend devices (normal suspend)
> >   loop of disable_irq()
> >     late suspend of devices
> >       _PTS
> >         disable nonboot CPUs
> >           local_irq_disable()
> >             sysdev suspend
> >               enter sleep state
> >               get control from the BIOS
> >             sysdev resume
> >             (*)
> >           local_irq_enable()
> >         enable nonboot CPUs
> >       _WAK
> >     early resume of devices
> >   loop of enable_irq()
> > resume devices (normal resume)
> > 
> > the ordering of _PTS with respect to putting devices into low power states and
> > disabling the nonboot CPUs will be the same as it is now and the same applies
> > to _WAK and putting devices into D0 etc. (I really _really_ wouldn't like to
> > change this ordering, since this alone is likely to break things badly).
> 
> Yes.
> 
> Also, make the "loop of disable/enable_irq()" phase be a helper function 
> that also sets system_state to SYSTEM_SUSPENDING/SYSTEM_RUNNING 
> respectively, and it should all be pretty clean, and the changes really 
> should be pretty minimal.

OK

So, I'm going to implement something along these lines.  We'll see how it
works out.

Thanks,
Rafael
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