usb: xhci: Program 'route string' in the input slot context

xHCI spec says: the values of the 'route string' field shall be
initialized by the first 'Address Device' command issued to a
device slot, and shall not be modified by any other command.

So far U-Boot does not program this field, and it does not prevent
SS device directly attached to root port, or HS device behind an HS
hub, from working, due to the fact that 'route string' is used by
the xHC to target SS packets. But in order to enumerate devices
behind an SS hub, this field must be programmed.

With this commit and along with previous commits, now SS & HS devices
attached to a USB 3.0 hub can be enumerated by U-Boot.

As usual, this new feature is only available when DM is on.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/usb/host/xhci-mem.c

@@ -723,6 +723,11 @@ void xhci_setup_addressable_virt_dev(struct xhci_ctrl *ctrl,
 	u64 trb_64 = 0;
 	int slot_id = udev->slot_id;
 	int speed = udev->speed;
+	int route = 0;
+#ifdef CONFIG_DM_USB
+	struct usb_device *dev = udev;
+	struct usb_hub_device *hub;
+#endif
 
 	virt_dev = ctrl->devs[slot_id];
 
@@ -733,7 +738,32 @@ void xhci_setup_addressable_virt_dev(struct xhci_ctrl *ctrl,
 	slot_ctx = xhci_get_slot_ctx(ctrl, virt_dev->in_ctx);
 
 	/* Only the control endpoint is valid - one endpoint context */
-	slot_ctx->dev_info |= cpu_to_le32(LAST_CTX(1) | 0);
+	slot_ctx->dev_info |= cpu_to_le32(LAST_CTX(1));
+
+#ifdef CONFIG_DM_USB
+	/* Calculate the route string for this device */
+	port_num = dev->portnr;
+	while (!usb_hub_is_root_hub(dev->dev)) {
+		hub = dev_get_uclass_priv(dev->dev);
+		/*
+		 * Each hub in the topology is expected to have no more than
+		 * 15 ports in order for the route string of a device to be
+		 * unique. SuperSpeed hubs are restricted to only having 15
+		 * ports, but FS/LS/HS hubs are not. The xHCI specification
+		 * says that if the port number the device is greater than 15,
+		 * that portion of the route string shall be set to 15.
+		 */
+		if (port_num > 15)
+			port_num = 15;
+		route |= port_num << (hub->hub_depth * 4);
+		dev = dev_get_parent_priv(dev->dev);
+		port_num = dev->portnr;
+		dev = dev_get_parent_priv(dev->dev->parent);
+	}
+
+	debug("route string %x\n", route);
+#endif
+	slot_ctx->dev_info |= route;
 
 	switch (speed) {
 	case USB_SPEED_SUPER: