drm/i915: Track the pinned kernel contexts on each engine

Each engine acquires a pin on the kernel contexts (normal and preempt)
so that the logical state is always available on demand. Keep track of
each engines pin by storing the returned pointer on the engine for quick
access.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308132522.21573-6-chris@chris-wilson.co.uk

1 files changed, 33 insertions, 32 deletions

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 1937128ea267..652c1b3ba190 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -641,12 +641,6 @@ void intel_engines_set_scheduler_caps(struct drm_i915_private *i915)
 		i915->caps.scheduler = 0;
 }
 
-static void __intel_context_unpin(struct i915_gem_context *ctx,
-				  struct intel_engine_cs *engine)
-{
-	intel_context_unpin(intel_context_lookup(ctx, engine));
-}
-
 struct measure_breadcrumb {
 	struct i915_request rq;
 	struct i915_timeline timeline;
@@ -697,6 +691,20 @@ out_frame:
 	return dw;
 }
 
+static int pin_context(struct i915_gem_context *ctx,
+		       struct intel_engine_cs *engine,
+		       struct intel_context **out)
+{
+	struct intel_context *ce;
+
+	ce = intel_context_pin(ctx, engine);
+	if (IS_ERR(ce))
+		return PTR_ERR(ce);
+
+	*out = ce;
+	return 0;
+}
+
 /**
  * intel_engines_init_common - initialize cengine state which might require hw access
  * @engine: Engine to initialize.
@@ -711,11 +719,8 @@ out_frame:
 int intel_engine_init_common(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *i915 = engine->i915;
-	struct intel_context *ce;
 	int ret;
 
-	engine->set_default_submission(engine);
-
 	/* We may need to do things with the shrinker which
 	 * require us to immediately switch back to the default
 	 * context. This can cause a problem as pinning the
@@ -723,36 +728,34 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
 	 * be available. To avoid this we always pin the default
 	 * context.
 	 */
-	ce = intel_context_pin(i915->kernel_context, engine);
-	if (IS_ERR(ce))
-		return PTR_ERR(ce);
+	ret = pin_context(i915->kernel_context, engine,
+			  &engine->kernel_context);
+	if (ret)
+		return ret;
 
 	/*
 	 * Similarly the preempt context must always be available so that
-	 * we can interrupt the engine at any time.
+	 * we can interrupt the engine at any time. However, as preemption
+	 * is optional, we allow it to fail.
 	 */
-	if (i915->preempt_context) {
-		ce = intel_context_pin(i915->preempt_context, engine);
-		if (IS_ERR(ce)) {
-			ret = PTR_ERR(ce);
-			goto err_unpin_kernel;
-		}
-	}
+	if (i915->preempt_context)
+		pin_context(i915->preempt_context, engine,
+			    &engine->preempt_context);
 
 	ret = measure_breadcrumb_dw(engine);
 	if (ret < 0)
-		goto err_unpin_preempt;
+		goto err_unpin;
 
 	engine->emit_fini_breadcrumb_dw = ret;
 
-	return 0;
+	engine->set_default_submission(engine);
 
-err_unpin_preempt:
-	if (i915->preempt_context)
-		__intel_context_unpin(i915->preempt_context, engine);
+	return 0;
 
-err_unpin_kernel:
-	__intel_context_unpin(i915->kernel_context, engine);
+err_unpin:
+	if (engine->preempt_context)
+		intel_context_unpin(engine->preempt_context);
+	intel_context_unpin(engine->kernel_context);
 	return ret;
 }
 
@@ -765,8 +768,6 @@ err_unpin_kernel:
  */
 void intel_engine_cleanup_common(struct intel_engine_cs *engine)
 {
-	struct drm_i915_private *i915 = engine->i915;
-
 	cleanup_status_page(engine);
 
 	intel_engine_fini_breadcrumbs(engine);
@@ -776,9 +777,9 @@ void intel_engine_cleanup_common(struct intel_engine_cs *engine)
 	if (engine->default_state)
 		i915_gem_object_put(engine->default_state);
 
-	if (i915->preempt_context)
-		__intel_context_unpin(i915->preempt_context, engine);
-	__intel_context_unpin(i915->kernel_context, engine);
+	if (engine->preempt_context)
+		intel_context_unpin(engine->preempt_context);
+	intel_context_unpin(engine->kernel_context);
 
 	i915_timeline_fini(&engine->timeline);