[Intel-gfx] [PATCH 5/6] drm/i915/scheduler: Boost priorities for flips

[Chris Wilson]

Boost the priority of any rendering required to show the next pageflip
as we want to avoid missing the vblank by being delayed by invisible
workload. We prioritise avoiding jank and jitter in the GUI over
starving background tasks.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h      |  5 ++++
 drivers/gpu/drm/i915/i915_gem.c      | 54 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_display.c |  2 ++
 3 files changed, 61 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a53c80172752..075ce2b503ed 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3386,6 +3386,11 @@ int i915_gem_object_wait(struct drm_i915_gem_object *obj,
 			 unsigned int flags,
 			 long timeout,
 			 struct intel_rps_client *rps);
+int i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
+				  unsigned int flags,
+				  int priority);
+#define I915_PRIORITY_DISPLAY 1024
+
 int __must_check
 i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj,
 				  bool write);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 5a29b2bf9750..055c9e48ebe6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -433,6 +433,60 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 	return timeout;
 }
 
+static void
+i915_gem_object_boost_fence(struct dma_fence *fence, int boost)
+{
+	struct drm_i915_gem_request *rq;
+	struct intel_engine_cs *engine;
+
+	if (!dma_fence_is_i915(fence))
+		return;
+
+	rq = to_request(fence);
+	if (i915_gem_request_completed(rq))
+		return;
+
+	engine = rq->engine;
+	if (!engine->schedule)
+		return;
+
+	engine->schedule(rq, rq->priotree.priority + boost);
+}
+
+int
+i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
+			      unsigned int flags,
+			      int boost)
+{
+	struct dma_fence *excl;
+
+	if (flags & I915_WAIT_ALL) {
+		struct dma_fence **shared;
+		unsigned int count, i;
+		int ret;
+
+		ret = reservation_object_get_fences_rcu(obj->resv,
+							&excl, &count, &shared);
+		if (ret)
+			return ret;
+
+		for (i = 0; i < count; i++) {
+			i915_gem_object_boost_fence(shared[i], boost);
+			dma_fence_put(shared[i]);
+		}
+
+		kfree(shared);
+	} else {
+		excl = reservation_object_get_excl_rcu(obj->resv);
+	}
+
+	if (excl) {
+		i915_gem_object_boost_fence(excl, boost);
+		dma_fence_put(excl);
+	}
+	return 0;
+}
+
 /**
  * Waits for rendering to the object to be completed
  * @obj: i915 gem object
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 39cda13b6267..45d21421a2be 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14213,6 +14213,8 @@ intel_prepare_plane_fb(struct drm_plane *plane,
 		}
 	}
 
+	i915_gem_object_wait_priority(obj, 0, I915_PRIORITY_DISPLAY);
+
 	return 0;
 }
 
-- 
2.10.1