linux-kernel - Re: [PATCH] i915 / PM: Fix crash while aborting hibernation (Re: [linux-pm] [regression] "drm/i915: implement new pm ops" disables irq on aborted s2disk)

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Message-Id: <201002081206.08946.rjw@sisk.pl>
Date:	Mon, 8 Feb 2010 12:06:08 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
Cc:	Zhenyu Wang <zhenyuw@...ux.intel.com>,
	Eric Anholt <eric@...olt.net>,
	linux-pm@...ts.linux-foundation.org,
	dri-devel@...ts.sourceforge.net,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i915 / PM: Fix crash while aborting hibernation (Re: [linux-pm] [regression] "drm/i915: implement new pm ops" disables irq on aborted s2disk)

On Monday 08 February 2010, Alan Jenkins wrote:
> Rafael J. Wysocki wrote:
> > On Thursday 04 February 2010, Zhenyu Wang wrote:
> >   
> >> On 2010.02.03 23:44:41 +0100, Rafael J. Wysocki wrote:
> >>     
> >>> On Wednesday 03 February 2010, Alan Jenkins wrote:
> >>>       
> >>>> Hi
> >>>>
> >>>> I found this regression on my EeePC 701 with modesetting enabled.  When 
> >>>> I hibernate using s2disk, I can abort the hibernation by pressing the 
> >>>> backspace key.  Doing so breaks X on 2.6.32-rc6 (but not 2.6.32).
> >>>>         
> >>> Yeah.
> >>>
> >>> To be honest, I knew that's going to happen, but didn't have the time to take
> >>> care of it.
> >>>
> >>> The problem is that i915 does literally _nothing_ in its .thaw() callback,
> >>> although it should at least reverse whatever .freeze() did to the hardware
> >>> (and memory allocations and so on), so that the adapter is functional
> >>> after creating the image.
> >>>
> >>> Fixing this requires some thought, though, because at the moment .freeze()
> >>> thinks it's .suspend(), which is not the case as this report clearly shows.
> >>> So, in fact i915_pci_suspend() has to be split into the .freeze() part and
> >>> the poweroff part cleanly and that's not  so simple (at least to me).
> >>>
> >>>       
> >> Right, I think that'll be more clean, stuff in i915_save/restore_state() need
> >> to be splited too, especially isolate stuff for mode setting and other device
> >> state, as what my original purpose for this is to remove extra mode setting 
> >> cycle in old behavior so not waste time for hibernate.
> >>     
> >
> > We can't really do that, because we'll need to restore the saved state at the
> > resume-from-hibernation stage.
> >
> > The appended patch fixes the issue for me, although it's been only tested
> > a little.  It sort of defeats the purpose of commit
> > cbda12d77ea590082edb6d30bd342a67ebc459e0, but I don't see any less invasive
> > way to fix this except maybe for reverting that commit entirely.
> >
> > Note that the drm_irq_[un]install() thing may be unnecessary, but I wasn't sure
> > about that and surely wouldn't suggest doing that for 2.6.33.  Also it looks like
> > some things from the freeze and thaw parts may be moved to the "low-level"
> > suspend and resume parts, respectively, but that would require some
> > i915_gem_* surgery I was too scared to do.
> >
> > Alan, please test, i915 guys, please review.
> >
> > Rafael
> >   
> 
> The patch works very nicely on my eeepc.

Great, thanks for testing.

> Thanks
> (and thanks again for all your hard work this cycle, and specifically 
> for pointing me to the s2disk hang-fix)

You're welcome. :-)

Rafael
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