thunderbolt: Enable/disable sideband depending on USB4 port offline mode

When USB4 port is in offline mode (this mean there is no device
attached) we want to keep the sideband up to make it possible to
communicate with the retimers. In the same way there is no need to
enable sideband transactions when the USB4 port is not offline as they
are already up.

For this reason make the enabling/disabling depend on the USB4 port
offline status.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/retimer.c

@@ -206,6 +206,15 @@ static void tb_retimer_set_inbound_sbtx(struct tb_port *port)
 {
 	int i;
 
+	/*
+	 * When USB4 port is online sideband communications are
+	 * already up.
+	 */
+	if (!usb4_port_device_is_offline(port->usb4))
+		return;
+
+	tb_port_dbg(port, "enabling sideband transactions\n");
+
 	for (i = 1; i <= TB_MAX_RETIMER_INDEX; i++)
 		usb4_port_retimer_set_inbound_sbtx(port, i);
 }
@@ -214,6 +223,16 @@ static void tb_retimer_unset_inbound_sbtx(struct tb_port *port)
 {
 	int i;
 
+	/*
+	 * When USB4 port is offline we need to keep the sideband
+	 * communications up to make it possible to communicate with
+	 * the connected retimers.
+	 */
+	if (usb4_port_device_is_offline(port->usb4))
+		return;
+
+	tb_port_dbg(port, "disabling sideband transactions\n");
+
 	for (i = TB_MAX_RETIMER_INDEX; i >= 1; i--)
 		usb4_port_retimer_unset_inbound_sbtx(port, i);
 }

drivers/thunderbolt/tb.h

@@ -1301,6 +1301,11 @@ struct usb4_port *usb4_port_device_add(struct tb_port *port);
 void usb4_port_device_remove(struct usb4_port *usb4);
 int usb4_port_device_resume(struct usb4_port *usb4);
 
+static inline bool usb4_port_device_is_offline(const struct usb4_port *usb4)
+{
+	return usb4->offline;
+}
+
 void tb_check_quirks(struct tb_switch *sw);
 
 #ifdef CONFIG_ACPI