[Intel-gfx] [PATCH 3/3] drm/i915: Check the ring is empty when declaring the engines are idle

Chris Wilson chris at chris-wilson.co.uk
Tue May 30 12:13:34 UTC 2017


As another precaution when testing whether the CS engine is actually
idle, also inspect the ring's HEAD/TAIL registers, which should be equal
when there are no commands left to execute by the GPU.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 699f2d3861c7..bc38bd128b76 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1212,6 +1212,11 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
 
 	intel_runtime_pm_get(dev_priv);
 
+	/* First check that no commands are left in the ring */
+	if ((I915_READ_HEAD(engine) & HEAD_ADDR) !=
+	    (I915_READ_TAIL(engine) & TAIL_ADDR))
+		idle = false;
+
 	/* No bit for gen2, so assume the CS parser is idle */
 	if (INTEL_GEN(dev_priv) > 2 && !(I915_READ_MODE(engine) & MODE_IDLE))
 		idle = false;
-- 
2.11.0



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