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

[Chris Wilson]

On Thu, Jun 01, 2017 at 12:03:18PM +0200, Michal Wajdeczko wrote:
> On Thu, Jun 01, 2017 at 10:04:46AM +0100, Chris Wilson wrote:
> > When we enable the GuC, we enable an alternative mechanism for doing
> > post-GGTT update invalidation. Likewise, when we disable the GuC, we
> > restore the previous method. Assert that we change between known
> > endpoints, so that we can catch if we accidentally clobber some other
> > gen and if we change the invalidate routine without updating guc.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Oscar Mateo <oscar.mateo at intel.com>
> > Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> > Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> > Cc: Arkadiusz Hiler <arkadiusz.hiler at intel.com>
> > Cc: Michel Thierry <michel.thierry at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_gtt.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index 1489c3af7145..4ff854e6413c 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -3095,13 +3095,17 @@ int i915_ggtt_enable_hw(struct drm_i915_private *dev_priv)
> >  
> >  void i915_ggtt_enable_guc(struct drm_i915_private *i915)
> >  {
> > +	GEM_BUG_ON(i915->ggtt.invalidate != gen6_ggtt_invalidate);
> > +
> >  	i915->ggtt.invalidate = guc_ggtt_invalidate;
> >  }
> >  
> >  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.

That's one of the reasons for adding it. So that if we forget to make
the change, it gets caught.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre