[Intel-gfx] [PATCH] drm/i915/guc: Assert that we switch between known ggtt->invalidate functions

[Joonas Lahtinen]

On to, 2017-06-01 at 12:03 +0200, Michal Wajdeczko wrote:
> On Thu, Jun 01, 2017 at 10:04:46AM +0100, Chris Wilson wrote:
> >  
> >  void i915_ggtt_disable_guc(struct drm_i915_private *i915)
> >  {
> > -	if (i915->ggtt.invalidate == guc_ggtt_invalidate)
> > -		i915->ggtt.invalidate = gen6_ggtt_invalidate;
> > +	/* We should only be called after i915_ggtt_enable_guc() */
> > +	GEM_BUG_ON(i915->ggtt.invalidate != guc_ggtt_invalidate);
> > +
> > +	i915->ggtt.invalidate = gen6_ggtt_invalidate;
> >  }
> 
> While this looks correct today, it may not work in the future if we
> will need somethig other than gen6_ggtt_invalidate() as base invalidate
> function or guc_gtt_invalidate() as the one for the guc. Just a head up.

Currently the assignment is directly to gen6_ggtt_invalidate, no
questions asked. So I don't think the assert could be much more :)

Maybe GuC code should backup the invalidate function before overriding.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation