linux-kernel - Re: [PATCH] don't suspend/resume 8xx chips

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Message-Id: <200803281313.03222.jesse.barnes@intel.com>
Date:	Fri, 28 Mar 2008 13:13:03 -0700
From:	Jesse Barnes <jesse.barnes@...el.com>
To:	Pavel Machek <pavel@....cz>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] don't suspend/resume 8xx chips

On Friday, March 28, 2008 7:40 am Pavel Machek wrote:
> On Wed 2008-03-26 16:28:12, Jesse Barnes wrote:
> > Recent testing has turned up some bugs in the new Intel suspend/resume
> > code for old, 8xx chipsets.  So for 2.6.25 it probably makes sense to
> > apply this patch, which should prevent the new code from getting called
> > on those chipsets.  We should have this fixed soon, but not in time for
> > 2.6.25 unfortunately.  Note that this patch (along with the
> > suspend/resume code in general) could use more testing.
> >
> > Signed-off-by:  Jesse Barnes <jesse.barnes@...el.com>
> >
> > diff --git a/drivers/char/drm/i915_dma.c b/drivers/char/drm/i915_dma.c
> > index e9d6663..6964a28 100644
> > --- a/drivers/char/drm/i915_dma.c
> > +++ b/drivers/char/drm/i915_dma.c
> > @@ -762,6 +762,11 @@ int i915_driver_load(struct drm_device *dev,
> > unsigned long
> >         unsigned long base, size;
> >         int ret = 0, mmio_bar = IS_I9XX(dev) ? 0 : 1;
> >
> > +       if (!IS_I9XX(dev)) {
> > +               dev->driver->suspend = NULL;
> > +               dev->driver->resume = NULL;
> > +       }
> > +
>
> Are you sure your driver needs no state saving?
>
> Maybe register suspend that printks, returns error?

No, there's definitely state we'd like to save/restore, but 8xx chips are 
tricky and we won't have them working before 2.6.25-final.  This patch 
preserves old behavior for 8xx chips and allows 9xx chips to properly survive 
suspend/resume events, so I don't think a printk is necessary.

Jesse
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