[Intel-gfx] [PATCH] drm/i915: Check engine->default_state mapping on module load

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-09-14 10:43:12)
> 
> On 14/09/2018 10:21, Chris Wilson wrote:
> > Check we can indeed acquire a WB mapping of the context image on module
> > load. Later this will give us the opportunity to validate that we can
> > switch from WC to WB as required.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_gem.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index be9d012d851b..37353afec66e 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -5424,6 +5424,7 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
> >   
> >       for_each_engine(engine, i915, id) {
> >               struct i915_vma *state;
> > +             void *vaddr;
> >   
> >               state = to_intel_context(ctx, engine)->state;
> >               if (!state)
> > @@ -5446,6 +5447,16 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
> >                       goto err_active;
> >   
> >               engine->default_state = i915_gem_object_get(state->obj);
> > +
> > +             /* Check we can acquire the image of the context state */
> > +             vaddr = i915_gem_object_pin_map(engine->default_state,
> > +                                             I915_MAP_WB);
> > +             if (IS_ERR(vaddr)) {
> > +                     err = PTR_ERR(vaddr);
> > +                     goto err_active;
> > +             }
> > +
> > +             i915_gem_object_unpin_map(engine->default_state);
> 
> Ah this perhaps strengthens the argument to have 
> __intel_engines_pin_default_state? (And the unpin pair.)

I hope it doesn't come to making this into an interface :)
Definitely not an idea I endorse, random manipulation of the
default_state.
 
> And I guess you made this patch come before the switch to WC since it is 
> not FORCE_WB here?

Yes, full sequence of patches in your inbox.
-Chris