[PATCH 04/72] drm/i915: Remove superfluous worker wakeups when RPS is already boosted

[Chris Wilson]

We only need to wake up the RPS worker once when initially enabling the
client boost, it remains in effect then until the last client no longer
requires the boost.

References: https://bugs.freedesktop.org/show_bug.cgi?id=102250
References: 7b92c1bd0540 ("drm/i915: Avoid keeping waitboost active for signaling threads")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_request.c | 6 ++++--
 drivers/gpu/drm/i915/intel_pm.c         | 9 ++++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 8efa9e7a9e46..794263421aa0 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -443,12 +443,14 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
 	engine->last_retired_context = request->ctx;
 
 	spin_lock_irq(&request->lock);
-	if (request->waitboost)
-		atomic_dec(&request->i915->gt_pm.rps.num_waiters);
 	if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &request->fence.flags))
 		dma_fence_signal_locked(&request->fence);
 	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags))
 		intel_engine_cancel_signaling(request);
+	if (request->waitboost) {
+		GEM_BUG_ON(!atomic_read(&request->i915->gt_pm.rps.num_waiters));
+		atomic_dec(&request->i915->gt_pm.rps.num_waiters);
+	}
 	spin_unlock_irq(&request->lock);
 
 	i915_priotree_fini(request->i915, &request->priotree);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index eb68abf6a8e9..5b36166976e3 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6372,12 +6372,15 @@ void gen6_rps_boost(struct drm_i915_gem_request *rq,
 	if (!rps->enabled)
 		return;
 
+	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags))
+		return;
+
+	/* Serializes with i915_gem_request_retire() */
 	boost = false;
 	spin_lock_irqsave(&rq->lock, flags);
-	if (!rq->waitboost && !i915_gem_request_completed(rq)) {
-		atomic_inc(&rps->num_waiters);
+	if (!rq->waitboost && !dma_fence_is_signaled_locked(&rq->fence)) {
+		boost = !atomic_fetch_inc(&rps->num_waiters);
 		rq->waitboost = true;
-		boost = true;
 	}
 	spin_unlock_irqrestore(&rq->lock, flags);
 	if (!boost)
-- 
2.16.1