diff --git a/sys/dev/drm/radeon/rv515.c b/sys/dev/drm/radeon/rv515.c
--- a/sys/dev/drm/radeon/rv515.c
+++ b/sys/dev/drm/radeon/rv515.c
@@ -1232,6 +1232,10 @@
 	struct drm_display_mode *mode1 = NULL;
 	struct rv515_watermark wm0_high, wm0_low;
 	struct rv515_watermark wm1_high, wm1_low;
+	memset(&wm0_high, 0, sizeof(wm0_high));
+	memset(&wm0_low, 0, sizeof(wm0_low));
+	memset(&wm1_high, 0, sizeof(wm1_high));
+	memset(&wm1_low, 0, sizeof(wm1_low));
 	u32 tmp;
 	u32 d1mode_priority_a_cnt, d1mode_priority_b_cnt;
 	u32 d2mode_priority_a_cnt, d2mode_priority_b_cnt;