drm/radeon: align ring writes to 16 dwords boundaries.

On some radeon GPUs this appears to introduce another level of
stability around interacting with the ring.

Its pretty much what fglrx appears to do.

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_cp.c b/drivers/gpu/drm/radeon/radeon_cp.c
index a18b3688a7f0..78a058fc039f 100644
--- a/drivers/gpu/drm/radeon/radeon_cp.c
+++ b/drivers/gpu/drm/radeon/radeon_cp.c
@@ -1950,3 +1950,35 @@ int radeon_driver_unload(struct drm_device *dev)
 	dev->dev_private = NULL;
 	return 0;
 }
+
+void radeon_commit_ring(drm_radeon_private_t *dev_priv)
+{
+	int i;
+	u32 *ring;
+	int tail_aligned;
+
+	/* check if the ring is padded out to 16-dword alignment */
+
+	tail_aligned = dev_priv->ring.tail & 0xf;
+	if (tail_aligned) {
+		int num_p2 = 16 - tail_aligned;
+
+		ring = dev_priv->ring.start;
+		/* pad with some CP_PACKET2 */
+		for (i = 0; i < num_p2; i++)
+			ring[dev_priv->ring.tail + i] = CP_PACKET2();
+
+		dev_priv->ring.tail += i;
+
+		dev_priv->ring.space -= num_p2 * sizeof(u32);
+	}
+
+	dev_priv->ring.tail &= dev_priv->ring.tail_mask;
+
+	DRM_MEMORYBARRIER();
+	GET_RING_HEAD( dev_priv );
+
+	RADEON_WRITE( RADEON_CP_RB_WPTR, dev_priv->ring.tail );
+	/* read from PCI bus to ensure correct posting */
+	RADEON_READ( RADEON_CP_RB_RPTR );
+}