drm/edid: Allow non-fatal checksum errors in CEA blocks

Switches will try to update the topology address and not correctly fix
up the checksum, so just let it slide.

https://bugs.freedesktop.org/28229

Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_edid.c

@@ -147,7 +147,10 @@ drm_edid_block_valid(u8 *raw_edid)
 		csum += raw_edid[i];
 	if (csum) {
 		DRM_ERROR("EDID checksum is invalid, remainder is %d\n", csum);
-		goto bad;
+
+		/* allow CEA to slide through, switches mangle this */
+		if (raw_edid[0] != 0x02)
+			goto bad;
 	}
 
 	/* per-block-type checks */