[PATCH 08/11] 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      | 50 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_display.c |  2 ++
 3 files changed, 57 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b8e72cdcb713..e21d3732244f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3406,6 +3406,11 @@ 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 I915_PRIORITY_MAX
+
 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 2878f03063aa..7c147b8b6c37 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -433,6 +433,56 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 	return timeout;
 }
 
+static void fence_set_priority(struct dma_fence *fence, int prio)
+{
+	struct drm_i915_gem_request *rq;
+	struct intel_engine_cs *engine;
+
+	if (!dma_fence_is_i915(fence))
+		return;
+
+	rq = to_request(fence);
+	engine = rq->engine;
+	if (!engine->schedule)
+		return;
+
+	engine->schedule(rq, prio);
+}
+
+int
+i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
+			      unsigned int flags,
+			      int prio)
+{
+	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++) {
+			fence_set_priority(shared[i], prio);
+			dma_fence_put(shared[i]);
+		}
+
+		kfree(shared);
+	} else {
+		excl = reservation_object_get_excl_rcu(obj->resv);
+	}
+
+	if (excl) {
+		fence_set_priority(excl, prio);
+		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 97589102442c..8df9554432a9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14761,6 +14761,8 @@ intel_prepare_plane_fb(struct drm_plane *plane,
 						      GFP_KERNEL);
 		if (ret < 0)
 			return ret;
+
+		i915_gem_object_wait_priority(obj, 0, I915_PRIORITY_DISPLAY);
 	}
 
 	if (plane->type == DRM_PLANE_TYPE_CURSOR &&
-- 
2.10.2