linux-kernel - Re: Regression from 2.6.26: Hibernation (possibly suspend) broken on Toshiba R500 (bisected)

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Date:	Thu, 4 Dec 2008 23:09:11 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Frans Pop <elendil@...net.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg KH <greg@...ah.com>, Ingo Molnar <mingo@...e.hu>,
	jbarnes@...tuousgeek.org, lenb@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	tiwai@...e.de, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Regression from 2.6.26: Hibernation (possibly suspend) broken on Toshiba R500 (bisected)

On Thursday, 4 of December 2008, Frans Pop wrote:
> On Wednesday 03 December 2008, Linus Torvalds wrote:
> > Well, I think that what _would_ be generally correct, and actually
> > pretty simple, is a rather different approach: just not sizing things
> > behind a transparent bridge AT ALL, since it really shouldn't matter.
> 
> I've given your patch a try and the few resumes from STR I've done were 
> all successful. That's not 100% conclusive yet, but a nice start.
> Some info from logs etc. below.

It doesn't help on my box, though.  I've got a failure to resume from
hibernation on the first attempt.

However, this one appears to work reliably for me (on top of vanilla current
mainline):

--- linux-2.6.orig/drivers/pci/setup-bus.c
+++ linux-2.6/drivers/pci/setup-bus.c
@@ -350,6 +350,11 @@ static int pbus_size_mem(struct pci_bus 
 
 			if (r->parent || (r->flags & mask) != type)
 				continue;
+
+			if ((dev->class >> 8) == PCI_CLASS_BRIDGE_CARDBUS
+			    && bus->self->transparent)
+				continue;
+
 			r_size = resource_size(r);
 			/* For bridges size != alignment */
 			align = resource_alignment(r);

> > > Also, I would be happy to actually understand _why_ this happens.
> >
> > 100% agreed. I do _not_ see why it should ever matter how we set up a
> > PCI bridging window - whether prefetchable or not - on a bridge that
> > should be transparent. It sounds really odd. I'm wondering if there is
> > something we're missing here.
> 
> The theory that it is really a resume issue and not a device layout issue 
> sounds logical. Especially as everything always works correctly after a 
> normal boot.

Well, in fact I'm pretty sure this is the case.  By changing memory address
space layout we effectively change conditions during suspend-resume and
apparently we can choose one for which the failure condition doesn't trigger
(or, IOW, the probability of it is _so_ small that we just can't see it).

There seems to be a race of some kind or a missing delay or something similar.

Thanks,
Rafael
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