[Intel-gfx] [PATCH 2/6] drm/i915: Treat kernel context as initialised

[Chris Wilson]

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.

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>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 45 +++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index a3b11aac23a4..3e3acd054f05 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -413,7 +413,8 @@ int i915_gem_context_init(struct drm_device *dev)
 		return PTR_ERR(ctx);
 	}
 
-	if (!i915.enable_execlists && ctx->engine[RCS].state) {
+	if (!i915.enable_execlists) {
+		struct intel_engine_cs *engine;
 		int ret;
 
 		/* We may need to do things with the shrinker which
@@ -423,13 +424,28 @@ int i915_gem_context_init(struct drm_device *dev)
 		 * be available. To avoid this we always pin the default
 		 * context.
 		 */
-		ret = i915_gem_obj_ggtt_pin(ctx->engine[RCS].state,
-					    get_context_alignment(dev_priv), 0);
-		if (ret) {
-			DRM_ERROR("Failed to pinned default global context (error %d)\n",
-				  ret);
-			i915_gem_context_unreference(ctx);
-			return ret;
+		for_each_engine(engine, dev_priv) {
+			struct intel_context *ce = &ctx->engine[engine->id];
+
+			ret = 0;
+			if (ce->state)
+				ret = i915_gem_obj_ggtt_pin(ce->state,
+							    get_context_alignment(dev_priv), 0);
+			if (ret) {
+				DRM_ERROR("Failed to pinned default global context (error %d)\n",
+					  ret);
+				i915_gem_context_unreference(ctx);
+				return ret;
+			}
+
+			/* The kernel context is only used as a placeholder
+			 * for flushing the active context. It is never used
+			 * for submitting rendering and as such never requires
+			 * the golden render context, and so we can skip
+			 * emitting it when we switch to the kernel context
+			 * (during eviction).
+			 */
+			ce->initialised = true;
 		}
 	}
 
@@ -452,13 +468,16 @@ 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 restore on enabling */
+	for_each_engine(engine, dev_priv) {
+		struct intel_context *ce =
+			&dev_priv->kernel_context->engine[engine->id];
+
+		ce->initialised =
+			!i915.enable_execlists || engine->init_context == NULL;
+	}
 	dev_priv->kernel_context->remap_slice = ALL_L3_SLICES(dev_priv);
 }
 
-- 
2.8.1