usb: xhci: Add port test modes support for usb2.

For usb2 ports, the port test mode Test_J_State, Test_K_State,
Test_Packet, Test_SE0_NAK and Test_Force_En can be enabled
as described in usb2 spec.

USB2 test mode is a required hardware feature for system integrators
validating their hardware according to USB spec, regarding signal
strength and stuff. It is purely a hardware test feature.

Usually you need an oscilloscope and have to enable those test modes on
the hardware. This will send some specific test patterns on D+/D-. There
is no report available (in Linux itself) as it is purely externally
visible. Regular USB usage is not possible at that time.
Anyone (well access to e.g. /dev/bus/usb/001/001 provided) can use it by
sending appropriate USB_PORT_FEAT_TEST requests to the hub.

[Add better commit message by Alexander Stein  -Mathias]
Signed-off-by: Guoqing Zhang <guoqing.zhang@intel.com>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 4e12c8c..675d552 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -425,6 +425,7 @@ struct xhci_op_regs {
 #define	PORT_L1DS_MASK		(0xff << 8)
 #define	PORT_L1DS(p)		(((p) & 0xff) << 8)
 #define	PORT_HLE		(1 << 16)
+#define PORT_TEST_MODE_SHIFT	28
 
 /* USB3 Protocol PORTLI  Port Link Information */
 #define PORT_RX_LANES(p)	(((p) >> 16) & 0xf)
@@ -1843,6 +1844,7 @@ struct xhci_hcd {
 	/* Compliance Mode Recovery Data */
 	struct timer_list	comp_mode_recovery_timer;
 	u32			port_status_u0;
+	u16			test_mode;
 /* Compliance Mode Timer Triggered every 2 seconds */
 #define COMP_MODE_RCVRY_MSECS 2000