drm/bridge: tc358767: Fix link properties discovery

When a display controller driver uses DRM_BRIDGE_ATTACH_NO_CONNECTOR,
tc358767 will behave properly and skip the creation of the connector.

However, tc_get_display_props(), which is used to find out about the DP
monitor and link, is only called from two places: .atomic_enable() and
tc_connector_get_modes(). The latter is only used when tc358767 creates
its own connector, i.e. when DRM_BRIDGE_ATTACH_NO_CONNECTOR is _not_
set.

Thus, the driver never finds out the link properties before get_edid()
is called. With num_lanes of 0 and link_rate of 0 there are not many
valid modes...

Fix this by adding tc_get_display_props() call at the beginning of
get_edid(), so that we have up to date information before looking at the
modes.

Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Closes: https://lore.kernel.org/all/24282420-b4dd-45b3-bb1c-fc37fe4a8205@siemens.com/
Fixes: de5e6c027ae6 ("drm/bridge: tc358767: add drm_panel_bridge support")
Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>
Tested-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231108-tc358767-v2-2-25c5f70a2159@ideasonboard.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index 159c95b..0c48e74 100644 (file)
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -1714,6 +1714,13 @@ static const struct drm_edid *tc_edid_read(struct drm_bridge *bridge,
                                           struct drm_connector *connector)
 {
        struct tc_data *tc = bridge_to_tc(bridge);
+       int ret;
+
+       ret = tc_get_display_props(tc);
+       if (ret < 0) {
+               dev_err(tc->dev, "failed to read display props: %d\n", ret);
+               return 0;
+       }
 
        return drm_edid_read_ddc(connector, &tc->aux.ddc);
 }