From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 6 Feb 2018 14:31:37 +0000
Subject: drm/i915: Remove superfluous worker wakeups when RPS is already
 boosted
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Git-commit: 253a281727d552200c4cddb0cc08cb2e95939603
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

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@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180206143137.15509-1-chris@chris-wilson.co.uk

Acked-by: Petr Tesarik <ptesarik@suse.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(-)

--- 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(stru
 	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);
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6374,12 +6374,15 @@ void gen6_rps_boost(struct drm_i915_gem_
 	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)