[Intel-gfx] [PATCH 35/44] drm/i915: Treat kernel context as initialised

[Chris Wilson]

On Thu, Jun 16, 2016 at 11:20:31AM +0300, Mika Kuoppala wrote:
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > The kernel context exists simply as a placeholder and should never be
> > executed with a render context. It does not need the golden render
> > state, as that will always be applied to a user context. By skipping the
> > initialisation we can avoid issues in attempting to program the golden
> > render context when trying to make the hardware idle.
> >
> > v2: Rebase
> >
> > Testcase: igt/drm_module_reload_basic #byt
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95634
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_context.c | 14 +++++++++-----
> >  drivers/gpu/drm/i915/intel_ringbuffer.c | 10 ++++++++++
> >  2 files changed, 19 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> > index c620fe6c9d96..60967b935d72 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> > @@ -434,13 +434,17 @@ void i915_gem_context_lost(struct drm_i915_private *dev_priv)
> >  			i915_gem_context_unpin(engine->last_context, engine);
> >  			engine->last_context = NULL;
> >  		}
> > -
> > -		/* Force the GPU state to be reinitialised on enabling */
> > -		dev_priv->kernel_context->engine[engine->id].initialised =
> > -			engine->init_context == NULL;
> >  	}
> >  
> > -	/* Force the GPU state to be reinitialised on enabling */
> > +	/* Force the GPU state to be restored on enabling */
> > +	if (!i915.enable_execlists) {
> > +		for_each_engine(engine, dev_priv) {
> > +			struct intel_context *kce =
> > +				&dev_priv->kernel_context->engine[engine->id];
> > +
> > +			kce->initialised = true;
> > +		}
> > +	}
> >  	dev_priv->kernel_context->remap_slice = ALL_L3_SLICES(dev_priv);
> >  }
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > index 86b80b4727fb..04a2d141e690 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -2338,6 +2338,16 @@ static int intel_ring_context_pin(struct i915_gem_context *ctx,
> >  			goto error;
> >  	}
> >  
> > +	/* The kernel context is only used as a placeholder for flushing the
> > +	 * active context. It is never used for submitting user rendering and
> > +	 * as such never requires the golden render context, and so we
> > can skip
> 
> But the kernel context does need a golden state. As that has been the
> guaranteed working context to go sleep (r6) with. Patch 42/44 will make
> it so?

No, the kernel context doesn't require it. The GPU "needs" that logical
state which is what patch 42 provides in the absence of any other
provider.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre