Re: [PATCH 2/6] drm/i915: Don't wait for page flips if there was GPU reset

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Feb 13, 2013 at 06:52:29PM +0200, Ville Syrjälä wrote:
> On Wed, Feb 13, 2013 at 04:23:27PM +0100, Daniel Vetter wrote:
> > On Tue, Jan 29, 2013 at 06:13:34PM +0200, ville.syrjala@linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > If a GPU reset occurs while a page flip has been submitted to the ring,
> > > the flip will never complete once the ring has been reset.
> > > 
> > > The GPU reset can be detected by sampling the reset_counter before the
> > > flip is submitted, and then while waiting for the flip, the sampled
> > > counter is compared with the current reset_counter value.
> > > 
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 14 +++++++++++++-
> > >  drivers/gpu/drm/i915/intel_drv.h     |  3 +++
> > >  2 files changed, 16 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index 4097118..e348a68 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -2862,10 +2862,12 @@ static bool intel_crtc_has_pending_flip(struct drm_crtc *crtc)
> > >  {
> > >  	struct drm_device *dev = crtc->dev;
> > >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > > +	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> > >  	unsigned long flags;
> > >  	bool pending;
> > >  
> > > -	if (i915_reset_in_progress(&dev_priv->gpu_error))
> > > +	if (i915_reset_in_progress(&dev_priv->gpu_error) ||
> > > +	    intel_crtc->reset_counter != atomic_read(&dev_priv->gpu_error.reset_counter))
> > >  		return false;
> > >  
> > >  	spin_lock_irqsave(&dev->event_lock, flags);
> > > @@ -6912,6 +6914,8 @@ static int intel_gen2_queue_flip(struct drm_device *dev,
> > >  	if (ret)
> > >  		goto err_unpin;
> > >  
> > > +	intel_crtc->reset_counter = atomic_read(&dev_priv->gpu_error.reset_counter);
> > 
> > Ok no bikeshed about ->reset_counter, but a different one: Why does this
> > need to be in the per-gen callback? Can't we just grab this before we call
> > down into these callbacks? Imo races wrt the reset/hang code don't matter
> > that much as long as we don't wait forever for a pageflip which won't
> > happen. Hanging the gpu concurrently to pageflipping is undefined anyway
> > right now ...
> 
> Yeah. It could be moved to happen a little earlier, and thus avoid the
> duplication.

Applied the patch and moved the assignment around a bit, thanks.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch