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

From: Rafael J. Wysocki
Date: Thu Dec 04 2008 - 17:10:45 EST

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

--- 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)
+ 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.

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