drm/i915: Add a hook for making the engines idle (parking) and unparking

In the next patch, we will want to install a callback when the engines
(GT as a whole) become idle and similarly when they first become busy.
To enable that callback, first rename intel_engines_mark_idle() to
intel_engines_park() and provide the companion intel_engines_unpark().
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025143943.7661-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3347,7 +3347,7 @@ i915_gem_idle_work_handler(struct work_struct *work)
 	if (!intel_engines_are_idle(dev_priv))
 		DRM_ERROR("Timeout waiting for engines to idle\n");
 
-	intel_engines_mark_idle(dev_priv);
+	intel_engines_park(dev_priv);
 	i915_gem_timelines_mark_idle(dev_priv);
 
 	GEM_BUG_ON(!dev_priv->gt.awake);

drivers/gpu/drm/i915/i915_gem_request.c

@@ -259,6 +259,8 @@ static void mark_busy(struct drm_i915_private *i915)
 	if (INTEL_GEN(i915) >= 6)
 		gen6_rps_busy(i915);
 
+	intel_engines_unpark(i915);
+
 	queue_delayed_work(i915->wq,
 			   &i915->gt.retire_work,
 			   round_jiffies_up_relative(HZ));

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -1600,19 +1600,48 @@ void intel_engines_reset_default_submission(struct drm_i915_private *i915)
 		engine->set_default_submission(engine);
 }
 
-void intel_engines_mark_idle(struct drm_i915_private *i915)
+/**
+ * intel_engines_park: called when the GT is transitioning from busy->idle
+ * @i915: the i915 device
+ *
+ * The GT is now idle and about to go to sleep (maybe never to wake again?).
+ * Time for us to tidy and put away our toys (release resources back to the
+ * system).
+ */
+void intel_engines_park(struct drm_i915_private *i915)
 {
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
 
 	for_each_engine(engine, i915, id) {
+		if (engine->park)
+			engine->park(engine);
+
 		intel_engine_disarm_breadcrumbs(engine);
-		i915_gem_batch_pool_fini(&engine->batch_pool);
 		tasklet_kill(&engine->execlists.irq_tasklet);
+
+		i915_gem_batch_pool_fini(&engine->batch_pool);
 		engine->execlists.no_priolist = false;
 	}
 }
 
+/**
+ * intel_engines_unpark: called when the GT is transitioning from idle->busy
+ * @i915: the i915 device
+ *
+ * The GT was idle and now about to fire up with some new user requests.
+ */
+void intel_engines_unpark(struct drm_i915_private *i915)
+{
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+
+	for_each_engine(engine, i915, id) {
+		if (engine->unpark)
+			engine->unpark(engine);
+	}
+}
+
 bool intel_engine_can_store_dword(struct intel_engine_cs *engine)
 {
 	switch (INTEL_GEN(engine->i915)) {

drivers/gpu/drm/i915/intel_lrc.c

@@ -1891,6 +1891,9 @@ static void execlists_set_default_submission(struct intel_engine_cs *engine)
 	engine->cancel_requests = execlists_cancel_requests;
 	engine->schedule = execlists_schedule;
 	engine->execlists.irq_tasklet.func = intel_lrc_irq_handler;
+
+	engine->park = NULL;
+	engine->unpark = NULL;
 }
 
 static void

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -2028,12 +2028,15 @@ static void i9xx_set_default_submission(struct intel_engine_cs *engine)
 {
 	engine->submit_request = i9xx_submit_request;
 	engine->cancel_requests = cancel_requests;
+
+	engine->park = NULL;
+	engine->unpark = NULL;
 }
 
 static void gen6_bsd_set_default_submission(struct intel_engine_cs *engine)
 {
+	i9xx_set_default_submission(engine);
 	engine->submit_request = gen6_bsd_submit_request;
-	engine->cancel_requests = cancel_requests;
 }
 
 static void intel_ring_default_vfuncs(struct drm_i915_private *dev_priv,

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -365,6 +365,9 @@ struct intel_engine_cs {
 	void		(*reset_hw)(struct intel_engine_cs *engine,
 				    struct drm_i915_gem_request *req);
 
+	void		(*park)(struct intel_engine_cs *engine);
+	void		(*unpark)(struct intel_engine_cs *engine);
+
 	void		(*set_default_submission)(struct intel_engine_cs *engine);
 
 	struct intel_ring *(*context_pin)(struct intel_engine_cs *engine,
@@ -868,7 +871,9 @@ bool intel_engines_are_idle(struct drm_i915_private *dev_priv);
 
 bool intel_engine_has_kernel_context(const struct intel_engine_cs *engine);
 
-void intel_engines_mark_idle(struct drm_i915_private *i915);
+void intel_engines_park(struct drm_i915_private *i915);
+void intel_engines_unpark(struct drm_i915_private *i915);
+
 void intel_engines_reset_default_submission(struct drm_i915_private *i915);
 
 bool intel_engine_can_store_dword(struct intel_engine_cs *engine);