[PATCH 2/2] drm/i915: Warn if ring tail is not qword aligned

[ville.syrjala@linux.intel.com]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Ringbuffer tail pointer must be qword aligned. Warn if someone
makes a mistake and forgets to pad the ring when the commands
inserted into the ring don't align to qword naturally.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 70a184e..79c8b13 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1275,6 +1275,8 @@ void intel_ring_advance(struct intel_ring_buffer *ring)
 	ring->tail &= ring->size - 1;
 	if (dev_priv->stop_rings & intel_ring_flag(ring))
 		return;
+	/* tail must be qword aligned */
+	WARN_ON(ring->tail & 7);
 	ring->write_tail(ring, ring->tail);
 }
 
-- 
1.7.8.6

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