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

[Wayne Lin <Wayne.Lin@amd.com>]

[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@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <sean@poorly.run>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Eryk Brol <eryk.brol@amd.com>
Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Cc: Nikola Cornij <nikola.cornij@amd.com>
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: "José Roberto de Souza" <jose.souza@intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.5+
Signed-off-by: Wayne Lin <Wayne.Lin@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