drm/i915: Store preemption capability in engine->flags

Let's avoid having to delve down the pointer chain to see if the i915
device has support for preemption and store that on the engine, which
made the decision in the first place!

v2: Refactor common preemption policy between execlists/guc.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tomasz Lis <tomasz.lis@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403183537.5522-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_guc_submission.c

@@ -657,6 +657,16 @@ static void port_assign(struct execlist_port *port, struct i915_request *rq)
 	port_set(port, i915_request_get(rq));
 }
 
+static inline int rq_prio(const struct i915_request *rq)
+{
+	return rq->priotree.priority;
+}
+
+static inline int port_prio(const struct execlist_port *port)
+{
+	return rq_prio(port_request(port));
+}
+
 static void guc_dequeue(struct intel_engine_cs *engine)
 {
 	struct intel_engine_execlists * const execlists = &engine->execlists;
@@ -672,12 +682,12 @@ static void guc_dequeue(struct intel_engine_cs *engine)
 	GEM_BUG_ON(rb_first(&execlists->queue) != rb);
 
 	if (port_isset(port)) {
-		if (engine->i915->preempt_context) {
+		if (intel_engine_has_preemption(engine)) {
 			struct guc_preempt_work *preempt_work =
 				&engine->i915->guc.preempt_work[engine->id];
+			int prio = execlists->queue_priority;
 
-			if (execlists->queue_priority >
-			    max(port_request(port)->priotree.priority, 0)) {
+			if (__execlists_need_preempt(prio, port_prio(port))) {
 				execlists_set_active(execlists,
 						     EXECLISTS_ACTIVE_PREEMPT);
 				queue_work(engine->i915->guc.preempt_wq,

drivers/gpu/drm/i915/intel_lrc.c

@@ -183,7 +183,8 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
 				const struct i915_request *last,
 				int prio)
 {
-	return engine->i915->preempt_context && prio > max(rq_prio(last), 0);
+	return (intel_engine_has_preemption(engine) &&
+		__execlists_need_preempt(prio, rq_prio(last)));
 }
 
 /**
@@ -2117,11 +2118,13 @@ static void execlists_set_default_submission(struct intel_engine_cs *engine)
 	engine->unpark = NULL;
 
 	engine->flags |= I915_ENGINE_SUPPORTS_STATS;
+	if (engine->i915->preempt_context)
+		engine->flags |= I915_ENGINE_HAS_PREEMPTION;
 
 	engine->i915->caps.scheduler =
 		I915_SCHEDULER_CAP_ENABLED |
 		I915_SCHEDULER_CAP_PRIORITY;
-	if (engine->i915->preempt_context)
+	if (intel_engine_has_preemption(engine))
 		engine->i915->caps.scheduler |= I915_SCHEDULER_CAP_PREEMPTION;
 }
 

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -562,6 +562,7 @@ struct intel_engine_cs {
 
 #define I915_ENGINE_NEEDS_CMD_PARSER BIT(0)
 #define I915_ENGINE_SUPPORTS_STATS   BIT(1)
+#define I915_ENGINE_HAS_PREEMPTION   BIT(2)
 	unsigned int flags;
 
 	/*
@@ -621,16 +622,29 @@ struct intel_engine_cs {
 	} stats;
 };
 
-static inline bool intel_engine_needs_cmd_parser(struct intel_engine_cs *engine)
+static inline bool
+intel_engine_needs_cmd_parser(const struct intel_engine_cs *engine)
 {
 	return engine->flags & I915_ENGINE_NEEDS_CMD_PARSER;
 }
 
-static inline bool intel_engine_supports_stats(struct intel_engine_cs *engine)
+static inline bool
+intel_engine_supports_stats(const struct intel_engine_cs *engine)
 {
 	return engine->flags & I915_ENGINE_SUPPORTS_STATS;
 }
 
+static inline bool
+intel_engine_has_preemption(const struct intel_engine_cs *engine)
+{
+	return engine->flags & I915_ENGINE_HAS_PREEMPTION;
+}
+
+static inline bool __execlists_need_preempt(int prio, int last)
+{
+	return prio > max(0, last);
+}
+
 static inline void
 execlists_set_active(struct intel_engine_execlists *execlists,
 		     unsigned int bit)