From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: Regression from 2.6.26: Hibernation (possibly suspend) broken on Toshiba R500 (bisected)
Date: Sat, 6 Dec 2008 14:53:23 +0100
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Cc: Frans Pop <elendil@planet.nl>, Greg KH <greg@kroah.com>,
       Ingo Molnar <mingo@elte.hu>, jbarnes@virtuousgeek.org, lenb@kernel.org,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, tiwai@suse.de,
       Andrew Morton <akpm@linux-foundation.org>
References: <200812020320.31876.rjw@sisk.pl> <alpine.LFD.2.00.0812051750450.3425@nehalem.linux-foundation.org> <200812060318.08532.rjw@sisk.pl>
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On Saturday, 6 of December 2008, Rafael J. Wysocki wrote:
> On Saturday, 6 of December 2008, Linus Torvalds wrote:
> > 
> > On Sat, 6 Dec 2008, Rafael J. Wysocki wrote:
> > >
> > > It only affects the legacy handling, but the non-legacy handling was left
> > > untouched.  IOW, the old "default" functions are still there and are being
> > > called by the "non-legacy" code (it's only used by USB at the moment, AFAICS).
> > 
> > Ok.
> > 
> > > Anyway, I did the test doing it only to the devices which don't have any
> > > non-default suspend-resume handling at all and _that_ apparently fixed the
> > > problem on my box. :-)
> > 
> > Which makes sense, btw. Because if you do the pci_save_state() on a device 
> > that _does_ have a suspend function, you'll be saving the post-suspend 
> > state - ie the device turned off.
> > 
> > So yeah, we really can only do the default suspend if the device has no 
> > pre-existing suspend function - or we'd need to make sure that all PCI 
> > drivers that do have suspend functions would only do the higher-level 
> > functionality.
> > 
> > Anyway, what I'm most interested in hearing is whether this actually 
> > improves your situation.
> 
> Yes, it does, from what I can tell at the moment. :-)

OK, this patch alone doesn't fix the problem, ie. I was able to reproduce it
with this patch applied, but it decreases the probability of a failure.

_However_, when I added two more patches to the mix:
- a patch that moved the PCI Express port suspend and resume to functions
  executed with interrupts disabled
- a patch that moves the restoration of the PCI config space in snd_hda_intel
  to a ->resume_early() callback
I'm not able to reproduce the problem any more (I did over 20
hibernation-resume cycles with this combination of patches applied with
occasional suspend-to-RAM-resume cycles in between and there were no problems
resuming).

I'm going to post the three patches in a separate thread for discussion.

Thanks,
Rafael
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