[Intel-gfx] [PATCH] drm/i915: Ignore SURFLIVE and flip counter when the GPU gets reset

[Chris Wilson]

On Wed, May 28, 2014 at 01:10:55PM +0100, Chris Wilson wrote:
> On Tue, May 27, 2014 at 09:33:09PM +0300, ville.syrjala at linux.intel.com wrote:
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 94ac51f..cb9dd8e 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -8895,6 +8895,10 @@ static bool page_flip_finished(struct intel_crtc *crtc)
> >  	struct drm_device *dev = crtc->base.dev;
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  
> > +	if (i915_reset_in_progress(&dev_priv->gpu_error) ||
> > +	    crtc->reset_counter != atomic_read(&dev_priv->gpu_error.reset_counter))
> > +		return true;
> 
> I really don't like this. The reset_count is incremented when the reset
> starts, so we shouldn't get here with
> crtc->reset_counter == gpu_error->reset_counter && reset_in_progress().
> 
> I'd prefer this to be
>  if (i915_has_reset(dev_priv, crtc->reset_counter)) return true;
> 
> with a guard when reading the gpu reset_counter:
> 
>  ret = i915_get_reset_counter(dev_priv, &intel_crtc->reset_counter);
>  if (ret)
> 	goto cleanup;
> 
> that does something like
> 
>  static inline int i915_get_reset_counter(struct drm_i915_private *dev_priv,
>                                           int *value)
>  {
>      *value = atomic_read(dev_priv->gpu_error.reset_counter);
>      if (*value & I915_WEDGED)
>      	return -EIO;
>      if (*value & I915_RESET_IN_PROGRESS_FLAG)
>         return -EAGAIN;
>      return 0;
>   }

Bleh, I've seen the light and this is overly complicated and doesn't
actually help make the code more readable than

if (intel_crtc->reset_counter != atomic_read(&dev_priv->gpu_error.reset_counter))
	return true;

The original patch is
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre