drm/i915: Limit ring synchronisation (sw sempahores) RPS boosts

Ring switches can occur many times per frame, and are often out of
control, causing frequent RPS boosting for no practical benefit. Treat
the sw semaphore synchronisation as a separate client and only allow it
to boost once per busy/idle cycle.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: s/rq/req/]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -2311,6 +2311,7 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
 			   list_empty(&file_priv->rps_boost) ? "" : ", active");
 		rcu_read_unlock();
 	}
+	seq_printf(m, "Semaphore boosts: %d\n", dev_priv->rps.semaphores.rps_boosts);
 	seq_printf(m, "Kernel boosts: %d\n", dev_priv->rps.boosts);
 
 	mutex_unlock(&dev_priv->rps.hw_lock);

drivers/gpu/drm/i915/i915_drv.h

@@ -272,6 +272,22 @@ struct drm_i915_private;
 struct i915_mm_struct;
 struct i915_mmu_object;
 
+struct drm_i915_file_private {
+	struct drm_i915_private *dev_priv;
+	struct drm_file *file;
+
+	struct {
+		spinlock_t lock;
+		struct list_head request_list;
+	} mm;
+	struct idr context_idr;
+
+	struct list_head rps_boost;
+	struct intel_engine_cs *bsd_ring;
+
+	unsigned rps_boosts;
+};
+
 enum intel_dpll_id {
 	DPLL_ID_PRIVATE = -1, /* non-shared dpll in use */
 	/* real shared dpll ids must be >= 0 */
@@ -1070,6 +1086,8 @@ struct intel_gen6_power_mgmt {
 	struct list_head clients;
 	unsigned boosts;
 
+	struct drm_i915_file_private semaphores;
+
 	/* manual wa residency calculations */
 	struct intel_rps_ei up_ei, down_ei;
 
@@ -2216,22 +2234,6 @@ static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst,
  * a later patch when the call to i915_seqno_passed() is obsoleted...
  */
 
-struct drm_i915_file_private {
-	struct drm_i915_private *dev_priv;
-	struct drm_file *file;
-
-	struct {
-		spinlock_t lock;
-		struct list_head request_list;
-	} mm;
-	struct idr context_idr;
-
-	struct list_head rps_boost;
-	struct intel_engine_cs *bsd_ring;
-
-	unsigned rps_boosts;
-};
-
 /*
  * A command that requires special handling by the command parser.
  */

drivers/gpu/drm/i915/i915_gem.c

@@ -3075,9 +3075,12 @@ __i915_gem_object_sync(struct drm_i915_gem_object *obj,
 		return ret;
 
 	if (!i915_semaphore_is_enabled(obj->base.dev)) {
+		struct drm_i915_private *i915 = to_i915(obj->base.dev);
 		ret = __i915_wait_request(req,
-					  atomic_read(&to_i915(obj->base.dev)->gpu_error.reset_counter),
-					  to_i915(obj->base.dev)->mm.interruptible, NULL, NULL);
+					  atomic_read(&i915->gpu_error.reset_counter),
+					  i915->mm.interruptible,
+					  NULL,
+					  &i915->rps.semaphores);
 		if (ret)
 			return ret;
 

drivers/gpu/drm/i915/intel_pm.c

@@ -6884,6 +6884,7 @@ void intel_pm_setup(struct drm_device *dev)
 	INIT_DELAYED_WORK(&dev_priv->rps.delayed_resume_work,
 			  intel_gen6_powersave_work);
 	INIT_LIST_HEAD(&dev_priv->rps.clients);
+	INIT_LIST_HEAD(&dev_priv->rps.semaphores.rps_boost);
 
 	dev_priv->pm.suspended = false;
 }