drm/amdgpu: change wptr to 64 bits (v2)

Newer asics need 64 bit wptrs.  If the wptr is now
smaller than the rptr that doesn't indicate a wrap-around
anymore.

v2: integrate Christian's comments.

Signed-off-by: Ken Wang <Qingqing.Wang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index cead88a..c9b536f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -232,7 +232,10 @@ int amdgpu_ring_init(struct amdgpu_device *adev, struct amdgpu_ring *ring,
 		}
 		amdgpu_ring_clear_ring(ring);
 	}
-	ring->ptr_mask = (ring->ring_size / 4) - 1;
+	ring->buf_mask = (ring->ring_size / 4) - 1;
+	ring->ptr_mask = ring->funcs->support_64bit_ptrs ?
+		0xffffffffffffffff : ring->buf_mask;
+
 	ring->max_dw = max_dw;
 
 	if (amdgpu_debugfs_ring_init(adev, ring)) {