On 2021-06-15 11:55 p.m., Wayne Lin wrote:
> [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....@amd.com>
> Fixes: 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid")
> Cc: Lyude Paul <ly...@redhat.com>
> Cc: Wayne Lin <wayne....@amd.com>
> Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
> Cc: Maxime Ripard <mrip...@kernel.org>
> Cc: Thomas Zimmermann <tzimmerm...@suse.de>
> Cc: dri-devel@lists.freedesktop.org
> Cc: <sta...@vger.kernel.org> # v5.5+
> ---
> 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 32b7f8983b94..b41b837db66d 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -2501,7 +2501,7 @@ 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;
> @@ -2533,7 +2533,6 @@ 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;
> @@ -2555,28 +2554,6 @@ 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)
> @@ -3410,8 +3387,15 @@ 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");
drm_dbg_kms takes a drm_device as first parameter.
Harry
> +
> mutex_unlock(&mgr->payload_lock);
> + return -EINVAL;
> + }
> }
> put_port = true;
> }
>
