Re: [PATCH 2/4] drm/i915: Restore the display config after a GPU reset on gen4

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, May 20, 2014 at 10:03:44AM +0200, Daniel Vetter wrote:
> On Mon, May 19, 2014 at 10:25:19PM +0300, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > On pre-ctg GPU reset also resets the display hardware. Force a mode
> > restore after the GPU reset, and also re-init clock gating.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > index b948c71..2ec3796 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -794,6 +794,14 @@ int i915_reset(struct drm_device *dev)
> >  		if (INTEL_INFO(dev)->gen > 5)
> >  			intel_reset_gt_powersave(dev);
> >  
> > +		if (IS_GEN4(dev) && !IS_G4X(dev)) {
> > +			intel_init_clock_gating(dev);
> > +
> > +			drm_modeset_lock_all(dev);
> > +			intel_modeset_setup_hw_state(dev, true);
> > +			drm_modeset_unlock_all(dev);
> 
> Locking inversion here. I think we need to push this down to the very end.

We already dropped struct_mutex a bit earlier. Or was there some other
lock you were worried about?

> Also this leaves the interesting question of what happens with vblank
> waits and friends ...

Hmm. I guess we might have some kind of refcount problem on our hands w/
vblanks and whatnot. Might be I'd need to for_each_crtc() .crtc_disable()
before the reset. That would match the g33 spec's recommendation to
disable all planes, but it also does quite a bit more, maybe too much?
But I could try it at least.

-- 
Ville Syrjälä
Intel OTC