[Intel-gfx] [PATCH 3/3] drm/i915: Boost GPU frequency if we detect outstanding pageflips

[Chris Wilson]

If we hit a vblank and see that have a pageflip queue but not yet
processed, ensure that the GPU is running at maximum in order to clear
the backlog. Pageflips are only queued for the following vblank, if we
miss it, there will be a visible stutter. Boosting the GPU frequency
doesn't prevent us from missing the target vblank, but it should help
the subsequent frames hitting theirs.

v2: Reorder vblank vs flip-complete so that we only check for a missed
flip after processing the completion events, and avoid spurious boosts.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h      |  1 +
 drivers/gpu/drm/i915/intel_display.c |  6 ++++++
 drivers/gpu/drm/i915/intel_drv.h     |  1 +
 drivers/gpu/drm/i915/intel_pm.c      | 15 +++++++++++++++
 4 files changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index f9450045a532..af050e439168 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -910,6 +910,7 @@ struct intel_gen6_power_mgmt {
 
 	bool enabled;
 	struct delayed_work delayed_resume_work;
+	struct work_struct boost_work;
 
 	/*
 	 * Protects RPS/RC6 register access and PCU communication.
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 54b69838e2de..3ad1529e74df 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9258,6 +9258,7 @@ void intel_check_page_flip(struct drm_device *dev, int pipe)
 	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	unsigned long flags;
+	bool outstanding;
 
 	if (crtc == NULL)
 		return;
@@ -9270,7 +9271,12 @@ void intel_check_page_flip(struct drm_device *dev, int pipe)
 		page_flip_completed(dev_priv, intel_crtc, intel_crtc->unpin_work);
 		intel_crtc->unpin_work = NULL;
 	}
+	outstanding = (intel_crtc->unpin_work != NULL &&
+		       crtc_sbc(intel_crtc) - intel_crtc->unpin_work->sbc > 1);
 	spin_unlock_irqrestore(&dev->event_lock, flags);
+
+	if (outstanding)
+		intel_queue_rps_boost(dev);
 }
 
 static int intel_crtc_page_flip(struct drm_crtc *crtc,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index b17c295fe967..a77f104db366 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -964,6 +964,7 @@ void ironlake_teardown_rc6(struct drm_device *dev);
 void gen6_update_ring_freq(struct drm_device *dev);
 void gen6_rps_idle(struct drm_i915_private *dev_priv);
 void gen6_rps_boost(struct drm_i915_private *dev_priv);
+void intel_queue_rps_boost(struct drm_device *dev);
 void intel_aux_display_runtime_get(struct drm_i915_private *dev_priv);
 void intel_aux_display_runtime_put(struct drm_i915_private *dev_priv);
 void intel_runtime_pm_get(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 00ab3c7a282d..dce2c268851f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6707,6 +6707,19 @@ int vlv_freq_opcode(struct drm_i915_private *dev_priv, int val)
 	return DIV_ROUND_CLOSEST(4 * mul * val, dev_priv->mem_freq) + 0xbd - 6;
 }
 
+static void __intel_rps_boost_work(struct work_struct *work)
+{
+	gen6_rps_boost(container_of(work, struct drm_i915_private, rps.boost_work));
+}
+
+void intel_queue_rps_boost(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+
+	if (INTEL_INFO(dev)->gen >= 6)
+		queue_work(dev_priv->wq, &dev_priv->rps.boost_work);
+}
+
 void intel_pm_setup(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -6715,6 +6728,8 @@ void intel_pm_setup(struct drm_device *dev)
 
 	INIT_DELAYED_WORK(&dev_priv->rps.delayed_resume_work,
 			  intel_gen6_powersave_work);
+	INIT_WORK(&dev_priv->rps.boost_work,
+		  __intel_rps_boost_work);
 
 	dev_priv->pm.suspended = false;
 	dev_priv->pm.irqs_disabled = false;
-- 
2.0.0.rc4