drm/i915: Don't downclock whilst we have clients waiting for GPU results

If we have clients stalled waiting for requests, ignore the GPU if it
signals that it should downclock due to low load. This helps prevent
the automatic timeout from causing extremely long running batches from
taking even longer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 557af88..707e2ca 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1070,6 +1070,18 @@
 	return events;
 }
 
+static bool any_waiters(struct drm_i915_private *dev_priv)
+{
+	struct intel_engine_cs *ring;
+	int i;
+
+	for_each_ring(ring, dev_priv, i)
+		if (ring->irq_refcount)
+			return true;
+
+	return false;
+}
+
 static void gen6_pm_rps_work(struct work_struct *work)
 {
 	struct drm_i915_private *dev_priv =
@@ -1114,6 +1126,8 @@
 			new_delay = dev_priv->rps.efficient_freq;
 			adj = 0;
 		}
+	} else if (any_waiters(dev_priv)) {
+		adj = 0;
 	} else if (pm_iir & GEN6_PM_RP_DOWN_TIMEOUT) {
 		if (dev_priv->rps.cur_freq > dev_priv->rps.efficient_freq)
 			new_delay = dev_priv->rps.efficient_freq;