--- a/sys/dev/drm/amd/amdgpu/gfx_v9_0.c
+++ b/sys/dev/drm/amd/amdgpu/gfx_v9_0.c
@@ -4759,6 +4759,11 @@ static const struct amdgpu_ring_funcs gfx
 		14 + /*	CE_META */
 		31 + /*	DE_META */
 		3 + /* CNTX_CTRL */
+		2 + /* FRAME_CONTROL (TMZ): amdgpu_ib_schedule() emits
+		       gfx_v9_0_ring_emit_tmz() unconditionally whenever
+		       ring->funcs->emit_tmz is set (amdgpu_ib.c:231-232),
+		       but this accounting never reserved space for it --
+		       submissions overran the ring allocation by 2 dw. */
 		5 + /* HDP_INVL */
 		8 + 8 + /* FENCE x2 */
 		2, /* SWITCH_BUFFER */