[Why] When we receive CSN message to notify one port is disconnected, we will implicitly set its corresponding num_slots to 0. Later on, we will eventually call drm_dp_update_payload_part1() to arrange down streams.

In drm_dp_update_payload_part1(), we iterate over all proposed_vcpis[] to do the update. Not specific to a target sink only. For example, if we light up 2 monitors, Monitor_A and Monitor_B, and then we unplug Monitor_B. Later on, when we call drm_dp_update_payload_part1() to try to update payload for Monitor_A, we'll also implicitly clean payload for Monitor_B at the same time. And finally, when we try to call drm_dp_update_payload_part1() to clean payload for Monitor_B, we will do nothing at this time since payload for Monitor_B has been cleaned up previously.

For StarTech 1to3 DP hub, it seems like if we didn't update DPCD payload ID table then polling for "ACT Handled"(BIT_1 of DPCD 002C0h) will fail and this polling will last for 3 seconds.

Therefore, guess the best way is we don't set the proposed_vcpi[] diretly. Let user of these herlper functions to set the proposed_vcpi directly.

[How] 1. Revert commit 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid") 2. Tackle the issue in previous commit by skipping those trasient proposed VCPIs. These stale VCPIs shoulde be explicitly cleared by user later on.

Changes since v1: * Change debug macro to use drm_dbg_kms() instead * Amend the commit message to add Fixed & Cc tags

Signed-off-by: Wayne Lin Wayne.Lin@amd.com Fixes: 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid") Cc: Lyude Paul lyude@redhat.com Cc: Wayne Lin Wayne.Lin@amd.com Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Cc: Maxime Ripard mripard@kernel.org Cc: Thomas Zimmermann tzimmermann@suse.de Cc: dri-devel@lists.freedesktop.org Cc: stable@vger.kernel.org # v5.5+ Signed-off-by: Lyude Paul lyude@redhat.com Link: https://patchwork.freedesktop.org/patch/msgid/20210616035501.3776-2-Wayne.Li... Reviewed-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/drm_dp_mst_topology.c | 36 ++++++++------------------- 1 file changed, 10 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index a08cc6b53bc2..702aa0711f80 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2499,7 +2499,7 @@ 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, old_input, ret, i; + int old_ddps, ret; u8 new_pdt; bool new_mcs; bool dowork = false, create_connector = false; @@ -2531,7 +2531,6 @@ 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->ldps = conn_stat->legacy_device_plug_status; port->ddps = conn_stat->displayport_device_plug_status; @@ -2554,28 +2553,6 @@ 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) - continue; - - 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) drm_modeset_unlock(&mgr->base.lock); else if (create_connector) @@ -3406,8 +3383,15 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr) port = drm_dp_mst_topology_get_port_validated( mgr, port); if (!port) { - mutex_unlock(&mgr->payload_lock); - return -EINVAL; + if (vcpi->num_slots == payload->num_slots) { + cur_slots += vcpi->num_slots; + payload->start_slot = req_payload.start_slot; + continue; + } else { + drm_dbg_kms("Fail:set payload to invalid sink"); + mutex_unlock(&mgr->payload_lock); + return -EINVAL; + } } put_port = true; }