[PATCH v2 21/27] drm/dp_mst: Don't forget to update port->input in drm_dp_mst_handle_conn_stat()

Lyude Paul
2019-09-03T20:48:45Z

This probably hasn't caused any problems up until now since it's
probably nearly impossible to encounter this in the wild, however if we
were to receive a connection status notification from the MST hub after
resume while we're in the middle of reprobing the link addresses for a
topology then there's a much larger chance that a port could have
changed from being an output port to input port (or vice versa). If we
forget to update this bit of information, we'll potentially ignore a
valid PDT change on a downstream port because we think it's an input
port.

So, make sure we read the input_port field in connection status
notifications in drm_dp_mst_handle_conn_stat() to prevent this from
happening once we've implemented suspend/resume reprobing.

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>
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 51 +++++++++++++++++++--------
1 file changed, 37 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 259634c5d6dc..e407aba1fbd2 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2078,18 +2078,23 @@ static void
drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
struct drm_dp_connection_status_notify *conn_stat)
{
- struct drm_device *dev = mstb->mgr->dev;
+ struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
+ struct drm_device *dev = mgr->dev;
struct drm_dp_mst_port *port;
- int old_ddps;
- bool dowork = false;
+ struct drm_connector *connector_to_destroy = NULL;
+ int old_ddps, ret;
+ u8 new_pdt;
+ bool dowork = false, create_connector = false;

port = drm_dp_get_port(mstb, conn_stat->port_number);
if (!port)
return;

+ mutex_lock(&port->lock);
drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);

old_ddps = port->ddps;
+ port->input = conn_stat->input_port;
port->mcs = conn_stat->message_capability_status;
port->ldps = conn_stat->legacy_device_plug_status;
port->ddps = conn_stat->displayport_device_plug_status;
@@ -2102,23 +2107,41 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
}
}

- if (!port->input) {
- int ret = drm_dp_port_set_pdt(port,
- conn_stat->peer_device_type);
- if (ret == 1) {
- dowork = true;
- } else if (ret < 0) {
- DRM_ERROR("Failed to change PDT for port %p: %d\n",
- port, ret);
- dowork = false;
- }
+ new_pdt = port->input ? DP_PEER_DEVICE_NONE : conn_stat->peer_device_type;
+
+ ret = drm_dp_port_set_pdt(port, new_pdt);
+ if (ret == 1) {
+ dowork = true;
+ } else if (ret < 0) {
+ DRM_ERROR("Failed to change PDT for port %p: %d\n",
+ port, ret);
+ dowork = false;
+ }
+
+ /*
+ * We unset port->connector before dropping connection_mutex so that
+ * there's no chance any of the atomic MST helpers can accidentally
+ * associate a to-be-destroyed connector with a port.
+ */
+ if (port->connector && port->input) {
+ connector_to_destroy = port->connector;
+ port->connector = NULL;
+ } else if (!port->connector && !port->input) {
+ create_connector = true;
}

drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+ if (connector_to_destroy)
+ mgr->cbs->destroy_connector(mgr, connector_to_destroy);
+ else if (create_connector)
+ drm_dp_mst_port_add_connector(mstb, port);
+
+ mutex_unlock(&port->lock);
+
drm_dp_mst_topology_put_port(port);
if (dowork)
queue_work(system_long_wq, &mstb->mgr->work);
-
}

static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_topology_mgr *mgr,
--
2.21.0