drm/display/dp_mst: Fix payload addition on a disconnected sink

commit 48b5c43ac2f67d9fe3d79d97d00f44acd5395abf upstream.

If an MST stream is enabled on a disconnected sink, the payload for the
stream is not created and the MST manager's payload count/next start VC
slot is not updated. Since the payload's start VC slot may still contain
a valid value (!= -1) the subsequent disabling of such a stream could
cause an incorrect decrease of the payload count/next start VC slot in
drm_dp_remove_payload() and hence later payload additions will fail.

Fix the above by marking the payload as invalid in the above case, so
that it's skipped during payload removal. While at it add a debug print
for this case.

Cc: Lyude Paul <lyude@redhat.com>
Cc: <stable@vger.kernel.org> # v6.1+
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214184258.2869417-3-imre.deak@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index d77858c7c4db9077a4c5f829d5aff52b940c02f6..e77c674b37ca2f5217767f328bbee3570acfc260 100644 (file)
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3309,8 +3309,13 @@ int drm_dp_add_payload_part1(struct drm_dp_mst_topology_mgr *mgr,
        int ret;
 
        port = drm_dp_mst_topology_get_port_validated(mgr, payload->port);
-       if (!port)
+       if (!port) {
+               drm_dbg_kms(mgr->dev,
+                           "VCPI %d for port %p not in topology, not creating a payload\n",
+                           payload->vcpi, payload->port);
+               payload->vc_start_slot = -1;
                return 0;
+       }
 
        if (mgr->payload_count == 0)
                mgr->next_start_slot = mst_state->start_slot;