[PATCH 48/87] drm/i915: Priority boost switching to an idle ring

[Chris Wilson]

In order to maximise concurrency between engines, if we queue a request
to a current idle ring, reorder its dependencies to execute that request
as early as possible and ideally improve occupancy of multiple engines
simultaneously.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_request.h | 5 +++--
 drivers/gpu/drm/i915/intel_lrc.c    | 3 +++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 1220c110f3b8..23798554b48f 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -86,10 +86,11 @@ enum {
 	I915_PRIORITY_INVALID = INT_MIN
 };
 
-#define I915_PRIORITY_SHIFT 1
+#define I915_PRIORITY_SHIFT 2
 #define I915_PRIORITY_MASK (-BIT(I915_PRIORITY_SHIFT))
 
-#define I915_PRIORITY_NEWCLIENT BIT(0)
+#define I915_PRIORITY_NEWCLIENT BIT(1)
+#define I915_PRIORITY_STALL BIT(0)
 
 struct i915_capture_list {
 	struct i915_capture_list *next;
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 043fa88b708f..8fe201a094e8 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1134,6 +1134,9 @@ static void execlists_schedule(struct i915_request *request, int prio)
 	if (i915_request_completed(request))
 		return;
 
+	if (RB_EMPTY_ROOT(&request->engine->execlists.queue.rb_root))
+		prio |= I915_PRIORITY_STALL;
+
 	if (prio <= READ_ONCE(request->priotree.priority))
 		return;
 
-- 
2.16.3