From: Chen-Yu Tsai <wens@csie.org>
Date: Fri, 8 Sep 2017 15:50:11 +0800
Subject: drm/sun4i: tcon: Check for multiple paths between TCONs and backends
Git-commit: 1469619d29d752759a2c9604a74091f92757830a
Patch-mainline: v4.15-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
The patch b317fa3ba11a ("drm/sun4i: tcon: Find matching display backend
by device node matching") assumed a one-to-one mapping between TCONs
and backends. This turned out wrong, as we found muxing controls in the
TCON of the A31, and undocumented usage of the backend output selector
of the A20.
Make sun4i_tcon_find_engine() bail out if the current node has multiple
input connections.
Fixes: b317fa3ba11a ("drm/sun4i: tcon: Find matching display backend
by device node matching")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170908075016.18657-4-wens@csie.org
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/sun4i/sun4i_tcon.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -473,6 +473,20 @@ static struct sunxi_engine *sun4i_tcon_f
if (!port)
return ERR_PTR(-EINVAL);
+ /*
+ * This only works if there is only one path from the TCON
+ * to any display engine. Otherwise the probe order of the
+ * TCONs and display engines is not guaranteed. They may
+ * either bind to the wrong one, or worse, bind to the same
+ * one if additional checks are not done.
+ *
+ * Bail out if there are multiple input connections.
+ */
+ if (of_get_available_child_count(port) != 1) {
+ of_node_put(port);
+ return ERR_PTR(-EINVAL);
+ }
+
for_each_available_child_of_node(port, ep) {
remote = of_graph_get_remote_port_parent(ep);
if (!remote)