drm/dp_mst: Handle SST-only branch device case

[Why]
While handling LINK_ADDRESS reply, current code expects a peer device
can handle sideband message once the peer device type is reported as
DP_PEER_DEVICE_MST_BRANCHING. However, when the connected device is
a SST branch case, it can't handle the sideband message(MST_CAP=0 in
DPCD 00021h).

Current code will try to send LINK_ADDRESS to SST branch device and end
up with message timeout and monitor can't display normally. As the
result of that, we should take SST branch device into account.

[How]
According to DP 1.4 spec, we can use Peer_Device_Type as
DP_PEER_DEVICE_MST_BRANCHING and Message_Capability_Status as 0 to
indicate peer device as a SST-only branch device.

Fix following:
- Add the function drm_dp_mst_is_dp_mst_end_device() to decide whether a
peer device connected to a DFP is mst end device. Which also indicates
if the peer device is capable of handling message or not.
- Take SST-only branch device case into account in
drm_dp_port_set_pdt() and add a new parameter 'new_mcs'. Take sst branch
device case as the same case as DP_PEER_DEVICE_DP_LEGACY_CONV and
DP_PEER_DEVICE_SST_SINK. All original handling logics remain.
- Take SST-only branch device case into account in
drm_dp_mst_port_add_connector().
- Fix some parts in drm_dp_mst_handle_link_address_port() to have SST
branch device case into consideration.
- Fix the arguments of drm_dp_port_set_pdt() in
drm_dp_mst_handle_conn_stat().
- Have SST branch device also report
connector_status_connected when the ddps is true
in drm_dp_mst_detect_port()
- Fix the arguments of drm_dp_port_set_pdt() in
drm_dp_delayed_destroy_port()

Changes since v1:(https://patchwork.kernel.org/patch/11323079/)
* Squash previous patch into one patch and merge the commit message here.
* Combine the if statements mentioned in comments

Fixes: c485e2c9 ("drm/dp_mst: Refactor pdt setup/teardown, add more locking")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200117060350.26358-2-Wayne.Lin@amd.com

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -1916,73 +1916,90 @@ static u8 drm_dp_calculate_rad(struct drm_dp_mst_port *port,
 	return parent_lct + 1;
 }
 
-static int drm_dp_port_set_pdt(struct drm_dp_mst_port *port, u8 new_pdt)
+static bool drm_dp_mst_is_dp_mst_end_device(u8 pdt, bool mcs)
+{
+	switch (pdt) {
+	case DP_PEER_DEVICE_DP_LEGACY_CONV:
+	case DP_PEER_DEVICE_SST_SINK:
+		return true;
+	case DP_PEER_DEVICE_MST_BRANCHING:
+		/* For sst branch device */
+		if (!mcs)
+			return true;
+
+		return false;
+	}
+	return true;
+}
+
+static int
+drm_dp_port_set_pdt(struct drm_dp_mst_port *port, u8 new_pdt,
+		    bool new_mcs)
 {
 	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
 	struct drm_dp_mst_branch *mstb;
 	u8 rad[8], lct;
 	int ret = 0;
 
-	if (port->pdt == new_pdt)
+	if (port->pdt == new_pdt && port->mcs == new_mcs)
 		return 0;
 
 	/* Teardown the old pdt, if there is one */
-	switch (port->pdt) {
-	case DP_PEER_DEVICE_DP_LEGACY_CONV:
-	case DP_PEER_DEVICE_SST_SINK:
-		/*
-		 * If the new PDT would also have an i2c bus, don't bother
-		 * with reregistering it
-		 */
-		if (new_pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
-		    new_pdt == DP_PEER_DEVICE_SST_SINK) {
-			port->pdt = new_pdt;
-			return 0;
-		}
+	if (port->pdt != DP_PEER_DEVICE_NONE) {
+		if (drm_dp_mst_is_dp_mst_end_device(port->pdt, port->mcs)) {
+			/*
+			 * If the new PDT would also have an i2c bus,
+			 * don't bother with reregistering it
+			 */
+			if (new_pdt != DP_PEER_DEVICE_NONE &&
+			    drm_dp_mst_is_dp_mst_end_device(new_pdt, new_mcs)) {
+				port->pdt = new_pdt;
+				port->mcs = new_mcs;
+				return 0;
+			}
 
-		/* remove i2c over sideband */
-		drm_dp_mst_unregister_i2c_bus(&port->aux);
-		break;
-	case DP_PEER_DEVICE_MST_BRANCHING:
-		mutex_lock(&mgr->lock);
-		drm_dp_mst_topology_put_mstb(port->mstb);
-		port->mstb = NULL;
-		mutex_unlock(&mgr->lock);
-		break;
+			/* remove i2c over sideband */
+			drm_dp_mst_unregister_i2c_bus(&port->aux);
+		} else {
+			mutex_lock(&mgr->lock);
+			drm_dp_mst_topology_put_mstb(port->mstb);
+			port->mstb = NULL;
+			mutex_unlock(&mgr->lock);
+		}
 	}
 
 	port->pdt = new_pdt;
-	switch (port->pdt) {
-	case DP_PEER_DEVICE_DP_LEGACY_CONV:
-	case DP_PEER_DEVICE_SST_SINK:
-		/* add i2c over sideband */
-		ret = drm_dp_mst_register_i2c_bus(&port->aux);
-		break;
+	port->mcs = new_mcs;
 
-	case DP_PEER_DEVICE_MST_BRANCHING:
-		lct = drm_dp_calculate_rad(port, rad);
-		mstb = drm_dp_add_mst_branch_device(lct, rad);
-		if (!mstb) {
-			ret = -ENOMEM;
-			DRM_ERROR("Failed to create MSTB for port %p", port);
-			goto out;
-		}
+	if (port->pdt != DP_PEER_DEVICE_NONE) {
+		if (drm_dp_mst_is_dp_mst_end_device(port->pdt, port->mcs)) {
+			/* add i2c over sideband */
+			ret = drm_dp_mst_register_i2c_bus(&port->aux);
+		} else {
+			lct = drm_dp_calculate_rad(port, rad);
+			mstb = drm_dp_add_mst_branch_device(lct, rad);
+			if (!mstb) {
+				ret = -ENOMEM;
+				DRM_ERROR("Failed to create MSTB for port %p",
+					  port);
+				goto out;
+			}
 
-		mutex_lock(&mgr->lock);
-		port->mstb = mstb;
-		mstb->mgr = port->mgr;
-		mstb->port_parent = port;
+			mutex_lock(&mgr->lock);
+			port->mstb = mstb;
+			mstb->mgr = port->mgr;
+			mstb->port_parent = port;
 
-		/*
-		 * Make sure this port's memory allocation stays
-		 * around until its child MSTB releases it
-		 */
-		drm_dp_mst_get_port_malloc(port);
-		mutex_unlock(&mgr->lock);
+			/*
+			 * Make sure this port's memory allocation stays
+			 * around until its child MSTB releases it
+			 */
+			drm_dp_mst_get_port_malloc(port);
+			mutex_unlock(&mgr->lock);
 
-		/* And make sure we send a link address for this */
-		ret = 1;
-		break;
+			/* And make sure we send a link address for this */
+			ret = 1;
+		}
 	}
 
 out:
@@ -2135,9 +2152,8 @@ drm_dp_mst_port_add_connector(struct drm_dp_mst_branch *mstb,
 		goto error;
 	}
 
-	if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
-	     port->pdt == DP_PEER_DEVICE_SST_SINK) &&
-	    port->port_num >= DP_MST_LOGICAL_PORT_0) {
+	if (port->pdt != DP_PEER_DEVICE_NONE &&
+	    drm_dp_mst_is_dp_mst_end_device(port->pdt, port->mcs)) {
 		port->cached_edid = drm_get_edid(port->connector,
 						 &port->aux.ddc);
 		drm_connector_set_tile_property(port->connector);
@@ -2201,6 +2217,7 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
 	struct drm_dp_mst_port *port;
 	int old_ddps = 0, ret;
 	u8 new_pdt = DP_PEER_DEVICE_NONE;
+	bool new_mcs = 0;
 	bool created = false, send_link_addr = false, changed = false;
 
 	port = drm_dp_get_port(mstb, port_msg->port_number);
@@ -2245,7 +2262,7 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
 	port->input = port_msg->input_port;
 	if (!port->input)
 		new_pdt = port_msg->peer_device_type;
-	port->mcs = port_msg->mcs;
+	new_mcs = port_msg->mcs;
 	port->ddps = port_msg->ddps;
 	port->ldps = port_msg->legacy_device_plug_status;
 	port->dpcd_rev = port_msg->dpcd_revision;
@@ -2272,7 +2289,7 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
 		}
 	}
 
-	ret = drm_dp_port_set_pdt(port, new_pdt);
+	ret = drm_dp_port_set_pdt(port, new_pdt, new_mcs);
 	if (ret == 1) {
 		send_link_addr = true;
 	} else if (ret < 0) {
@@ -2286,7 +2303,8 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
 	 * we're coming out of suspend. In this case, always resend the link
 	 * address if there's an MSTB on this port
 	 */
-	if (!created && port->pdt == DP_PEER_DEVICE_MST_BRANCHING)
+	if (!created && port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
+	    port->mcs)
 		send_link_addr = true;
 
 	if (port->connector)
@@ -2323,6 +2341,7 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
 	struct drm_dp_mst_port *port;
 	int old_ddps, old_input, ret, i;
 	u8 new_pdt;
+	bool new_mcs;
 	bool dowork = false, create_connector = false;
 
 	port = drm_dp_get_port(mstb, conn_stat->port_number);
@@ -2354,7 +2373,6 @@ 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->mcs = conn_stat->message_capability_status;
 	port->ldps = conn_stat->legacy_device_plug_status;
 	port->ddps = conn_stat->displayport_device_plug_status;
 
@@ -2367,8 +2385,8 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
 	}
 
 	new_pdt = port->input ? DP_PEER_DEVICE_NONE : conn_stat->peer_device_type;
-
-	ret = drm_dp_port_set_pdt(port, new_pdt);
+	new_mcs = conn_stat->message_capability_status;
+	ret = drm_dp_port_set_pdt(port, new_pdt, new_mcs);
 	if (ret == 1) {
 		dowork = true;
 	} else if (ret < 0) {
@@ -3929,6 +3947,8 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
 	switch (port->pdt) {
 	case DP_PEER_DEVICE_NONE:
 	case DP_PEER_DEVICE_MST_BRANCHING:
+		if (!port->mcs)
+			ret = connector_status_connected;
 		break;
 
 	case DP_PEER_DEVICE_SST_SINK:
@@ -4541,7 +4561,7 @@ drm_dp_delayed_destroy_port(struct drm_dp_mst_port *port)
 	if (port->connector)
 		port->mgr->cbs->destroy_connector(port->mgr, port->connector);
 
-	drm_dp_port_set_pdt(port, DP_PEER_DEVICE_NONE);
+	drm_dp_port_set_pdt(port, DP_PEER_DEVICE_NONE, port->mcs);
 	drm_dp_mst_put_port_malloc(port);
 }