[PATCH 05/16] drm/i915: Boost GPU clocks if we miss the pageflip's vblank

[Chris Wilson]

If we miss the current vblank because the gpu was busy, that may cause a
jitter as the frame rate temporarily drops. We try to limit the impact
of this by then boosting the GPU clock to deliver the frame as quickly
as possible. Originally done in commit 6ad790c0f5ac ("drm/i915: Boost GPU
frequency if we detect outstanding pageflips") but was never forward
ported to atomic and finally dropped in commit fd3a40242e87 ("drm/i915:
Rip out legacy page_flip completion/irq handling").

References: https://bugs.freedesktop.org/show_bug.cgi?id=102199
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 59 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h     |  1 -
 drivers/gpu/drm/i915/intel_pm.c      | 42 ++-----------------------
 3 files changed, 62 insertions(+), 40 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3b95cf953335..69a750ef5794 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12636,6 +12636,55 @@ static const struct drm_crtc_funcs intel_crtc_funcs = {
 	.set_crc_source = intel_crtc_set_crc_source,
 };
 
+struct wait_rps_boost {
+	struct wait_queue_entry wait;
+
+	struct drm_crtc *crtc;
+	struct drm_i915_gem_request *request;
+};
+
+static int do_rps_boost(struct wait_queue_entry *_wait,
+			unsigned mode, int sync, void *key)
+{
+	struct wait_rps_boost *wait = container_of(_wait, typeof(*wait), wait);
+	struct drm_i915_gem_request *rq = wait->request;
+
+	gen6_rps_boost(rq, NULL);
+	i915_gem_request_put(rq);
+
+	drm_crtc_vblank_put(wait->crtc);
+
+	list_del(&wait->wait.entry);
+	kfree(wait);
+	return 1;
+}
+
+static void add_rps_boost_after_vblank(struct drm_crtc *crtc,
+				       struct dma_fence *fence)
+{
+	struct wait_rps_boost *wait;
+
+	if (!dma_fence_is_i915(fence))
+		return;
+
+	if (drm_crtc_vblank_get(crtc))
+		return;
+
+	wait = kmalloc(sizeof(*wait), GFP_KERNEL);
+	if (!wait) {
+		drm_crtc_vblank_put(crtc);
+		return;
+	}
+
+	wait->request = to_request(dma_fence_get(fence));
+	wait->crtc = crtc;
+
+	wait->wait.func = do_rps_boost;
+	wait->wait.flags = 0;
+
+	add_wait_queue(drm_crtc_vblank_waitqueue(crtc), &wait->wait);
+}
+
 /**
  * intel_prepare_plane_fb - Prepare fb for usage on plane
  * @plane: drm plane to prepare for
@@ -12733,12 +12782,22 @@ intel_prepare_plane_fb(struct drm_plane *plane,
 		return ret;
 
 	if (!new_state->fence) { /* implicit fencing */
+		struct dma_fence *fence;
+
 		ret = i915_sw_fence_await_reservation(&intel_state->commit_ready,
 						      obj->resv, NULL,
 						      false, I915_FENCE_TIMEOUT,
 						      GFP_KERNEL);
 		if (ret < 0)
 			return ret;
+
+		fence = reservation_object_get_excl_rcu(obj->resv);
+		if (fence) {
+			add_rps_boost_after_vblank(new_state->crtc, fence);
+			dma_fence_put(fence);
+		}
+	} else {
+		add_rps_boost_after_vblank(new_state->crtc, new_state->fence);
 	}
 
 	return 0;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 2940d393ecfd..34b5fc190411 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1845,7 +1845,6 @@ void gen6_rps_reset_ei(struct drm_i915_private *dev_priv);
 void gen6_rps_idle(struct drm_i915_private *dev_priv);
 void gen6_rps_boost(struct drm_i915_gem_request *rq,
 		    struct intel_rps_client *rps);
-void intel_queue_rps_boost_for_request(struct drm_i915_gem_request *req);
 void g4x_wm_get_hw_state(struct drm_device *dev);
 void vlv_wm_get_hw_state(struct drm_device *dev);
 void ilk_wm_get_hw_state(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 68187bcfded4..d5ff0b9f999f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6169,6 +6169,7 @@ void gen6_rps_boost(struct drm_i915_gem_request *rq,
 		    struct intel_rps_client *rps)
 {
 	struct drm_i915_private *i915 = rq->i915;
+	unsigned long flags;
 	bool boost;
 
 	/* This is intentionally racy! We peek at the state here, then
@@ -6178,13 +6179,13 @@ void gen6_rps_boost(struct drm_i915_gem_request *rq,
 		return;
 
 	boost = false;
-	spin_lock_irq(&rq->lock);
+	spin_lock_irqsave(&rq->lock, flags);
 	if (!rq->waitboost && !i915_gem_request_completed(rq)) {
 		atomic_inc(&i915->rps.num_waiters);
 		rq->waitboost = true;
 		boost = true;
 	}
-	spin_unlock_irq(&rq->lock);
+	spin_unlock_irqrestore(&rq->lock, flags);
 	if (!boost)
 		return;
 
@@ -9155,43 +9156,6 @@ int intel_freq_opcode(struct drm_i915_private *dev_priv, int val)
 		return DIV_ROUND_CLOSEST(val, GT_FREQUENCY_MULTIPLIER);
 }
 
-struct request_boost {
-	struct work_struct work;
-	struct drm_i915_gem_request *req;
-};
-
-static void __intel_rps_boost_work(struct work_struct *work)
-{
-	struct request_boost *boost = container_of(work, struct request_boost, work);
-	struct drm_i915_gem_request *req = boost->req;
-
-	if (!i915_gem_request_completed(req))
-		gen6_rps_boost(req, NULL);
-
-	i915_gem_request_put(req);
-	kfree(boost);
-}
-
-void intel_queue_rps_boost_for_request(struct drm_i915_gem_request *req)
-{
-	struct request_boost *boost;
-
-	if (req == NULL || INTEL_GEN(req->i915) < 6)
-		return;
-
-	if (i915_gem_request_completed(req))
-		return;
-
-	boost = kmalloc(sizeof(*boost), GFP_ATOMIC);
-	if (boost == NULL)
-		return;
-
-	boost->req = i915_gem_request_get(req);
-
-	INIT_WORK(&boost->work, __intel_rps_boost_work);
-	queue_work(req->i915->wq, &boost->work);
-}
-
 void intel_pm_setup(struct drm_i915_private *dev_priv)
 {
 	mutex_init(&dev_priv->rps.hw_lock);
-- 
2.14.1