drm/i915: Use a high priority wq for nonblocking plane updates

system_unbound_wq can't keep up sometimes and we get dropped frames.
Switch to a high priority variant.
Reported-by: Heinrich Fink <heinrich.fink@daqri.com>
Tested-by: Heinrich Fink <heinrich.fink@daqri.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190910121347.22958-1-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/display/intel_display.c

@@ -14272,7 +14272,7 @@ static int intel_atomic_commit(struct drm_device *dev,
 	if (nonblock && state->modeset) {
 		queue_work(dev_priv->modeset_wq, &state->base.commit_work);
 	} else if (nonblock) {
-		queue_work(system_unbound_wq, &state->base.commit_work);
+		queue_work(dev_priv->flip_wq, &state->base.commit_work);
 	} else {
 		if (state->modeset)
 			flush_workqueue(dev_priv->modeset_wq);
@@ -16181,6 +16181,8 @@ int intel_modeset_init(struct drm_device *dev)
 	int ret;
 
 	dev_priv->modeset_wq = alloc_ordered_workqueue("i915_modeset", 0);
+	dev_priv->flip_wq = alloc_workqueue("i915_flip", WQ_HIGHPRI |
+					    WQ_UNBOUND, WQ_UNBOUND_MAX_ACTIVE);
 
 	drm_mode_config_init(dev);
 
@@ -17139,6 +17141,7 @@ void intel_modeset_driver_remove(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
+	flush_workqueue(dev_priv->flip_wq);
 	flush_workqueue(dev_priv->modeset_wq);
 
 	flush_work(&dev_priv->atomic_helper.free_work);
@@ -17175,6 +17178,7 @@ void intel_modeset_driver_remove(struct drm_device *dev)
 
 	intel_gmbus_teardown(dev_priv);
 
+	destroy_workqueue(dev_priv->flip_wq);
 	destroy_workqueue(dev_priv->modeset_wq);
 
 	intel_fbc_cleanup_cfb(dev_priv);

drivers/gpu/drm/i915/i915_drv.h

@@ -1438,6 +1438,8 @@ struct drm_i915_private {
 
 	/* ordered wq for modesets */
 	struct workqueue_struct *modeset_wq;
+	/* unbound hipri wq for page flips/plane updates */
+	struct workqueue_struct *flip_wq;
 
 	/* Display functions */
 	struct drm_i915_display_funcs display;