[PATCH 1/4] drm/dp_mst: Don't report ports connected if nothing is attached to them

[Imre Deak]

Reporting a port as connected if nothing is attached to them leads to
any i2c transactions on this port trying to use an uninitialized i2c
adapter, fix this.

Let's account for this case even if branch devices have no good reason
to report a port as unplugged with their peer device type set to 'none'.

Fixes: db1a07956968 ("drm/dp_mst: Handle SST-only branch device case")
References: https://gitlab.freedesktop.org/drm/intel/-/issues/2987
References: https://gitlab.freedesktop.org/drm/intel/-/issues/1963
Cc: Wayne Lin <Wayne.Lin at amd.com>
Cc: Lyude Paul <lyude at redhat.com>
Cc: <stable at vger.kernel.org> # v5.5+
Cc: intel-gfx at lists.freedesktop.org
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e82b596d646c..deb7995f42fa 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4224,6 +4224,7 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
 
 	switch (port->pdt) {
 	case DP_PEER_DEVICE_NONE:
+		break;
 	case DP_PEER_DEVICE_MST_BRANCHING:
 		if (!port->mcs)
 			ret = connector_status_connected;
-- 
2.25.1