[PATCH 2/4] drm/dp_mst: Only create connector for connected end device

[Wayne Lin]

[Why]
Currently, we will create connectors for all output ports no matter
it's connected or not. However, in MST, we can only determine
whether an output port really stands for a "connector" till it is
connected and check its peer device type as an end device.

In current code, we have chance to create connectors for output ports
connected with branch device and these are redundant connectors. e.g.
StarTech 1-to-4 DP hub is constructed by internal 2 layer 1-to-2 branch
devices. Creating connectors for such internal output ports are
redundant.

[How]
Put constraint on creating connector for connected end device only.

Fixes: 6f85f73821f6 ("drm/dp_mst: Add basic topology reprobing when resuming")
Cc: Juston Li <juston.li at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Harry Wentland <hwentlan at amd.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Sean Paul <sean at poorly.run>
Cc: Lyude Paul <lyude at redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
Cc: Eryk Brol <eryk.brol at amd.com>
Cc: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
Cc: Nikola Cornij <nikola.cornij at amd.com>
Cc: Wayne Lin <Wayne.Lin at amd.com>
Cc: "Ville Syrjälä" <ville.syrjala at linux.intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Manasi Navare <manasi.d.navare at intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
Cc: "José Roberto de Souza" <jose.souza at intel.com>
Cc: Sean Paul <seanpaul at chromium.org>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: dri-devel at lists.freedesktop.org
Cc: <stable at vger.kernel.org> # v5.5+
Signed-off-by: Wayne Lin <Wayne.Lin at amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 51cd7f74f026..f13c7187b07f 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2474,7 +2474,8 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
 
 	if (port->connector)
 		drm_modeset_unlock(&mgr->base.lock);
-	else if (!port->input)
+	else if (!port->input && port->pdt != DP_PEER_DEVICE_NONE &&
+		 drm_dp_mst_is_end_device(port->pdt, port->mcs))
 		drm_dp_mst_port_add_connector(mstb, port);
 
 	if (send_link_addr && port->mstb) {
@@ -2557,6 +2558,10 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
 		dowork = false;
 	}
 
+	if (!port->input && !port->connector && new_pdt != DP_PEER_DEVICE_NONE &&
+	    drm_dp_mst_is_end_device(new_pdt, new_mcs))
+		create_connector = true;
+
 	if (port->connector)
 		drm_modeset_unlock(&mgr->base.lock);
 	else if (create_connector)
-- 
2.17.1