diff --git a/sys/dev/drm/radeon/radeon_display.c b/sys/dev/drm/radeon/radeon_display.c
--- a/sys/dev/drm/radeon/radeon_display.c
+++ b/sys/dev/drm/radeon/radeon_display.c
@@ -959,6 +959,9 @@
 	unsigned target_clock = pll->flags & RADEON_PLL_USE_FRAC_FB_DIV ?
 		freq : freq / 10;
 
+	if (target_clock == 0)
+		return;
+
 	unsigned fb_div_min, fb_div_max, fb_div;
 	unsigned post_div_min, post_div_max, post_div;
 	unsigned ref_div_min, ref_div_max, ref_div;