drm/i915/scheduler: Boost priorities for flips

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.

v2: Descend dma_fence_array when boosting priorities.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161114204105.29171-10-chris@chris-wilson.co.uk

1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7a43f2a73552..3fb5e66e4d65 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -34,6 +34,7 @@
 #include "intel_drv.h"
 #include "intel_frontbuffer.h"
 #include "intel_mocs.h"
+#include <linux/dma-fence-array.h>
 #include <linux/reservation.h>
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
@@ -434,6 +435,70 @@ 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);
+}
+
+static void fence_set_priority(struct dma_fence *fence, int prio)
+{
+	/* Recurse once into a fence-array */
+	if (dma_fence_is_array(fence)) {
+		struct dma_fence_array *array = to_dma_fence_array(fence);
+		int i;
+
+		for (i = 0; i < array->num_fences; i++)
+			__fence_set_priority(array->fences[i], prio);
+	} else {
+		__fence_set_priority(fence, 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