usb: hub: Update handling connect status/change in usb_scan_port()

It was observed that on Intel MinnowMax board, when xHCI is enabled
in the BayTrail SoC, with a USB 3.0 device connected to the bottom
USB 3.0 port (mapped to xHCI root port #7), its PORTSC register is
always 0x201203 (CCS = 1, CSC = 0). The root cause of such behavior
is unknown yet. Connect status change bit is set on the same port
with a USB 2.0 device (mapped to xHCI port #1, which is a different
port on the root hub).

With current logic in usb_scan_port(), the enumeration process will
abort if it does not detect a connect status change on a hub port.
However since a device connection status is correctly reported, the
enumeration process can still continue.

With this change, USB device connected to the bottom blue port on
MinnowMax board can be enumerated under either SS or HS mode.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
Tested-by: Dinh Nguyen <dinguyen@kernel.org>

common/usb_hub.c

@@ -405,8 +405,15 @@ static int usb_scan_port(struct usb_device_scan *usb_scan)
 	portchange = le16_to_cpu(portsts->wPortChange);
 	debug("Port %d Status %X Change %X\n", i + 1, portstatus, portchange);
 
-	/* No connection change happened, wait a bit more. */
-	if (!(portchange & USB_PORT_STAT_C_CONNECTION)) {
+	/*
+	 * No connection change happened, wait a bit more.
+	 *
+	 * For some situation, the hub reports no connection change but a
+	 * device is connected to the port (eg: CCS bit is set but CSC is not
+	 * in the PORTSC register of a root hub), ignore such case.
+	 */
+	if (!(portchange & USB_PORT_STAT_C_CONNECTION) &&
+	    !(portstatus & USB_PORT_STAT_CONNECTION)) {
 		if (get_timer(0) >= hub->connect_timeout) {
 			debug("devnum=%d port=%d: timeout\n",
 			      dev->devnum, i + 1);
@@ -418,10 +425,6 @@ static int usb_scan_port(struct usb_device_scan *usb_scan)
 		return 0;
 	}
 
-	/* Test if the connection came up, and if not exit */
-	if (!(portstatus & USB_PORT_STAT_CONNECTION))
-		return 0;
-
 	/* A new USB device is ready at this point */
 	debug("devnum=%d port=%d: USB dev found\n", dev->devnum, i + 1);