Re: [PATCH v5 07/14] drm/dp_mst: Don't forget to update port->input in drm_dp_mst_handle_conn_stat()

On Mon, Oct 21, 2019 at 10:36:02PM -0400, Lyude Paul wrote:

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 Reviewed-by: Sean Paul sean@poorly.run

---

drivers/gpu/drm/drm_dp_mst_topology.c | 52 +++++++++++++++++++-------- 1 file changed, 38 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 7bf4db91ff90..c8e218b902ae 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2079,18 +2079,40 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; struct drm_dp_mst_port *port;

• int old_ddps;
• bool dowork = false;

• 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;

• /* Locking is only needed if the port's exposed to userspace */
• if (port->connector)

• if (port->connector) {

• if (!port->input && conn_stat->input_port) {
  

• 	/*
  

• 	 * We can't remove a connector from an already exposed
  

• 	 * port, so just throw the port out and make sure we
  

• 	 * reprobe the link address of it's parent MSTB
  

• 	 */
  

• 	drm_dp_mst_topology_unlink_port(mgr, port);
  

• 	mstb->link_address_sent = false;
  

• 	dowork = true;
  

• 	goto out;
  

• }
  

• /*
  

•  * Locking is only needed if the port's exposed to userspace
  

•  */
  

optional nit: this will still fit on one line

drm_modeset_lock(&mgr->base.lock, NULL);

• } else if (port->input && !conn_stat->input_port) {

• create_connector = true;
  

• /* Reprobe link address so we get num_sdp_streams */
  

• mstb->link_address_sent = false;
  

• dowork = true;
  

• }

  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;

@@ -2103,21 +2125,23 @@ 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;
  

  }

  if (port->connector) drm_modeset_unlock(&mgr->base.lock);

• else if (create_connector)

• drm_dp_mst_port_add_connector(mstb, port);
  
  

+out: drm_dp_mst_topology_put_port(port); if (dowork) queue_work(system_long_wq, &mstb->mgr->work); -- 2.21.0