[PATCH] drm/dp_mst: clear time slots for ports invalid

Lin, Wayne Wayne.Lin at amd.com
Fri Dec 20 01:46:08 UTC 2019

[AMD Official Use Only - Internal Distribution Only]

Hi, can someone help to review please.

Thanks a lot.


From: Wayne Lin <Wayne.Lin at amd.com>
Sent: Friday, December 6, 2019 16:39
To: dri-devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org
Cc: Kazlauskas, Nicholas; Wentland, Harry; Zuo, Jerry; lyude at redhat.com; stable at vger.kernel.org; Lin, Wayne
Subject: [PATCH] drm/dp_mst: clear time slots for ports invalid

When change the connection status in a MST topology, mst device
which detect the event will send out CONNECTION_STATUS_NOTIFY messgae.

e.g. src-mst-mst-sst => src-mst (unplug) mst-sst

Currently, under the above case of unplugging device, ports which have
been allocated payloads and are no longer in the topology still occupy
time slots and recorded in proposed_vcpi[] of topology manager.

If we don't clean up the proposed_vcpi[], when code flow goes to try to
update payload table by calling drm_dp_update_payload_part1(), we will
fail at checking port validation due to there are ports with proposed
time slots but no longer in the mst topology. As the result of that, we
will also stop updating the DPCD payload table of down stream port.

While handling the CONNECTION_STATUS_NOTIFY message, add a detection to
see if the event indicates that a device is unplugged to an output port.
If the detection is true, then iterrate over all proposed_vcpi[] to
see whether a port of the proposed_vcpi[] is still in the topology or
not. If the port is invalid, set its num_slots to 0.

Thereafter, when try to update payload table by calling
drm_dp_update_payload_part1(), we can successfully update the DPCD
payload table of down stream port and clear the proposed_vcpi[] to NULL.

Signed-off-by: Wayne Lin <Wayne.Lin at amd.com>
Cc: stable at vger.kernel.org
 drivers/gpu/drm/drm_dp_mst_topology.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 5306c47dc820..2e236b6275c4 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2318,7 +2318,7 @@ 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, ret;
+       int old_ddps, old_input, ret, i;
        u8 new_pdt;
        bool dowork = false, create_connector = false;

@@ -2349,6 +2349,7 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,

        old_ddps = port->ddps;
+       old_input = port->input;
        port->input = conn_stat->input_port;
        port->mcs = conn_stat->message_capability_status;
        port->ldps = conn_stat->legacy_device_plug_status;
@@ -2373,6 +2374,27 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
                dowork = false;

+       if (!old_input && old_ddps != port->ddps && !port->ddps) {
+               for (i = 0; i < mgr->max_payloads; i++) {
+                       struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i];
+                       struct drm_dp_mst_port *port_validated;
+                       if (vcpi) {
+                               port_validated =
+                                       container_of(vcpi, struct drm_dp_mst_port, vcpi);
+                               port_validated =
+                                       drm_dp_mst_topology_get_port_validated(mgr, port_validated);
+                               if (!port_validated) {
+                                       mutex_lock(&mgr->payload_lock);
+                                       vcpi->num_slots = 0;
+                                       mutex_unlock(&mgr->payload_lock);
+                               } else {
+                                       drm_dp_mst_topology_put_port(port_validated);
+                               }
+                       }
+               }
+       }
        if (port->connector)
        else if (create_connector)

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