linux-kernel - Re: commit "radeonfb: Fix resume from D3Cold on some platforms" breaks resume from RAM on PowerBook

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Message-Id: <1236638264.7260.192.camel@pasglop>
Date:	Tue, 10 Mar 2009 09:37:44 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Gaudenz Steinlin <gaudenz@...iologie.ch>
Cc:	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: commit "radeonfb: Fix resume from D3Cold on some platforms"
 breaks resume from RAM on PowerBook

On Fri, 2009-03-06 at 12:41 +0100, Gaudenz Steinlin wrote:

> > Another thing you can try in radeonfb_pci_resume():
> > 
> >         if (pdev->dev.power.power_state.event == PM_EVENT_SUSPEND) {
> > +		pci_restore_state(pdev);
> 
> Adding this fixes the bug. Apparently the PCI core does not fully
> restore the state. Before your suggestions I also tried to find out
> which part of your commit breaks resume and I found out that if I
> reinsert the parts to save and restore the pci configuration the bug is
> fixed. It seems that somehow the PCI coniguration is not fully restored [1].  

Ok so this doesn't make sense to me at this stage... I see two
possibilities:

 1- You haven't properly done the test disabling the early resume hack
(ie, you may have done it with also CPU_FREQ disabled for example) and
got a false negative there. The platform code calls into the early
resume stuff before the PCI core gets a chance to restore things so that
would be an explanation. I'll send a patch fixing that.

or

 2- For some reason, the core call to pci_raw_set_power_state() from
pci_restore_standard_config() is returning an error. That would cause
the later not to restore the rest of the config.

So what I suggest is that while keeping your added pci_restore_state()
in there, you also add some printk's in pci_restore_standard_config() to
see anything weird happens in there or if it appears to properly call
pci_restore_state(). It would be useful for us to know.

Cheers,
Ben.

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