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

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 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
 	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 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
 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 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
  */
 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);
 

drivers/gpu/drm/i915/intel_engine_types.h

@@ -231,11 +231,6 @@ struct intel_engine_execlists {
 	 */
 	u32 *csb_status;
 
-	/**
-	 * @preempt_context: the HW context for injecting preempt-to-idle
-	 */
-	struct intel_context *preempt_context;
-
 	/**
 	 * @preempt_complete_status: expected CSB upon completing preemption
 	 */
@@ -271,6 +266,9 @@ struct intel_engine_cs {
 
 	struct i915_timeline timeline;
 
+	struct intel_context *kernel_context; /* pinned */
+	struct intel_context *preempt_context; /* pinned; optional */
+
 	struct drm_i915_gem_object *default_state;
 	void *pinned_default_state;
 

drivers/gpu/drm/i915/intel_guc_ads.c

@@ -121,8 +121,7 @@ int intel_guc_ads_create(struct intel_guc *guc)
 	 * to find it. Note that we have to skip our header (1 page),
 	 * because our GuC shared data is there.
 	 */
-	kernel_ctx_vma = intel_context_lookup(dev_priv->kernel_context,
-					      dev_priv->engine[RCS0])->state;
+	kernel_ctx_vma = dev_priv->engine[RCS0]->kernel_context->state;
 	blob->ads.golden_context_lrca =
 		intel_guc_ggtt_offset(guc, kernel_ctx_vma) + skipped_offset;
 

drivers/gpu/drm/i915/intel_lrc.c

@@ -626,7 +626,7 @@ static void port_assign(struct execlist_port *port, struct i915_request *rq)
 static void inject_preempt_context(struct intel_engine_cs *engine)
 {
 	struct intel_engine_execlists *execlists = &engine->execlists;
-	struct intel_context *ce = execlists->preempt_context;
+	struct intel_context *ce = engine->preempt_context;
 	unsigned int n;
 
 	GEM_BUG_ON(execlists->preempt_complete_status !=
@@ -2321,7 +2321,7 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 
 	engine->flags |= I915_ENGINE_HAS_SEMAPHORES;
 	engine->flags |= I915_ENGINE_SUPPORTS_STATS;
-	if (engine->i915->preempt_context)
+	if (engine->preempt_context)
 		engine->flags |= I915_ENGINE_HAS_PREEMPTION;
 }
 
@@ -2423,14 +2423,9 @@ static int logical_ring_init(struct intel_engine_cs *engine)
 	}
 
 	execlists->preempt_complete_status = ~0u;
-	if (i915->preempt_context) {
-		struct intel_context *ce =
-			intel_context_lookup(i915->preempt_context, engine);
-
-		execlists->preempt_context = ce;
+	if (engine->preempt_context)
 		execlists->preempt_complete_status =
-			upper_32_bits(ce->lrc_desc);
-	}
+			upper_32_bits(engine->preempt_context->lrc_desc);
 
 	execlists->csb_status =
 		&engine->status_page.addr[I915_HWS_CSB_BUF0_INDEX];

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1735,8 +1735,7 @@ static inline int mi_set_context(struct i915_request *rq, u32 flags)
 		 * placeholder we use to flush other contexts.
 		 */
 		*cs++ = MI_SET_CONTEXT;
-		*cs++ = i915_ggtt_offset(intel_context_lookup(i915->kernel_context,
-							      engine)->state) |
+		*cs++ = i915_ggtt_offset(engine->kernel_context->state) |
 			MI_MM_SPACE_GTT |
 			MI_RESTORE_INHIBIT;
 	}

drivers/gpu/drm/i915/selftests/mock_engine.c

@@ -233,7 +233,8 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
 	timer_setup(&engine->hw_delay, hw_delay_complete, 0);
 	INIT_LIST_HEAD(&engine->hw_queue);
 
-	if (IS_ERR(intel_context_pin(i915->kernel_context, &engine->base)))
+	if (pin_context(i915->kernel_context, &engine->base,
+			&engine->base.kernel_context))
 		goto err_breadcrumbs;
 
 	return &engine->base;
@@ -276,7 +277,7 @@ void mock_engine_free(struct intel_engine_cs *engine)
 	if (ce)
 		intel_context_unpin(ce);
 
-	__intel_context_unpin(engine->i915->kernel_context, engine);
+	intel_context_unpin(engine->kernel_context);
 
 	intel_engine_fini_breadcrumbs(engine);
 	i915_timeline_fini(&engine->timeline);