[Intel-gfx] [PATCH 1/3] drm/i915/ringbuffer: Clear semaphore sync registers on ring init

[Chris Wilson]

Ensure that the sync registers are cleared every time we restart the
ring to avoid stale values from creeping in from random neutrinos.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index e18a64d41843..82c844488755 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -529,6 +529,13 @@ static int init_ring_common(struct intel_engine_cs *engine)
 
 	intel_engine_reset_breadcrumbs(engine);
 
+	if (HAS_LEGACY_SEMAPHORES(engine->i915)) {
+		I915_WRITE(RING_SYNC_0(engine->mmio_base), 0);
+		I915_WRITE(RING_SYNC_1(engine->mmio_base), 0);
+		if (HAS_VEBOX(dev_priv))
+			I915_WRITE(RING_SYNC_2(engine->mmio_base), 0);
+	}
+
 	/* Enforce ordering by reading HEAD register back */
 	I915_READ_HEAD(engine);
 
-- 
2.20.0.rc1