drm/edid: Skip empty CVT codepoints

Signed-off-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_edid.c

@@ -911,11 +911,15 @@ static int drm_cvt_modes(struct drm_connector *connector,
 	struct drm_device *dev = connector->dev;
 	struct cvt_timing *cvt;
 	const int rates[] = { 60, 85, 75, 60, 50 };
+	const u8 empty[3] = { 0, 0, 0 };
 
 	for (i = 0; i < 4; i++) {
 		int uninitialized_var(width), height;
 		cvt = &(timing->data.other_data.data.cvt[i]);
 
+		if (!memcmp(cvt->code, empty, 3))
+			continue;
+
 		height = (cvt->code[0] + ((cvt->code[1] & 0xf0) << 8) + 1) * 2;
 		switch (cvt->code[1] & 0xc0) {
 		case 0x00: