thunderbolt: Handle bandwidth allocation mode enablement notification

When the graphics side enables bandwidth allocation mode the DP IN
adapter sends notification to the connection manager about this.
Currently the handler misses this and tries to allocate 0 Mb/s that then
makes the graphics side to think the request failed.

Fix this by properly handling the enablement notification.

Fixes: 6ce3563520 ("thunderbolt: Add support for DisplayPort bandwidth allocation mode")
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/tb.c

@@ -1746,11 +1746,15 @@ static void tb_handle_dp_bandwidth_request(struct work_struct *work)
 		goto unlock;
 	}
 
-	requested_bw = usb4_dp_port_requested_bw(in);
-	if (requested_bw < 0) {
-		tb_port_dbg(in, "no bandwidth request active\n");
+	ret = usb4_dp_port_requested_bw(in);
+	if (ret < 0) {
+		if (ret == -ENODATA)
+			tb_port_dbg(in, "no bandwidth request active\n");
+		else
+			tb_port_warn(in, "failed to read requested bandwidth\n");
 		goto unlock;
 	}
+	requested_bw = ret;
 
 	tb_port_dbg(in, "requested bandwidth %d Mb/s\n", requested_bw);
 

drivers/thunderbolt/usb4.c

@@ -2732,7 +2732,8 @@ int usb4_dp_port_allocate_bw(struct tb_port *port, int bw)
  * Reads the DPCD (graphics driver) requested bandwidth and returns it
  * in Mb/s. Takes the programmed granularity into account. In case of
  * error returns negative errno. Specifically returns %-EOPNOTSUPP if
- * the adapter does not support bandwidth allocation mode.
+ * the adapter does not support bandwidth allocation mode, and %ENODATA
+ * if there is no active bandwidth request from the graphics driver.
  */
 int usb4_dp_port_requested_bw(struct tb_port *port)
 {
@@ -2750,10 +2751,10 @@ int usb4_dp_port_requested_bw(struct tb_port *port)
 	ret = tb_port_read(port, &val, TB_CFG_PORT,
 			   port->cap_adap + ADP_DP_CS_8, 1);
 	if (ret)
-		return 0;
+		return ret;
 
 	if (!(val & ADP_DP_CS_8_DR))
-		return 0;
+		return -ENODATA;
 
 	return (val & ADP_DP_CS_8_REQUESTED_BW_MASK) * granularity;
 }