USB: GADGET: optionally force full-speed for net2280 UDC

This patch (as1656) adds a module parameter to the net2280 UDC driver
to force full-speed operation.  It is intended for testing purposes,
where one wants to check how well a full-speed device performs when
attached to a high-speed bus.  Without this parameter it would be
necessary to interpose a full-speed hub; otherwise the net2280 would
connect at high speed.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/net2280.c

@@ -116,6 +116,10 @@ static bool enable_suspend = 0;
 /* "modprobe net2280 enable_suspend=1" etc */
 module_param (enable_suspend, bool, S_IRUGO);
 
+/* force full-speed operation */
+static bool full_speed;
+module_param(full_speed, bool, 0444);
+MODULE_PARM_DESC(full_speed, "force full-speed mode -- for testing only!");
 
 #define	DIR_STRING(bAddress) (((bAddress) & USB_DIR_IN) ? "in" : "out")
 
@@ -1899,6 +1903,10 @@ static int net2280_start(struct usb_gadget *_gadget,
 	retval = device_create_file (&dev->pdev->dev, &dev_attr_queues);
 	if (retval) goto err_func;
 
+	/* Enable force-full-speed testing mode, if desired */
+	if (full_speed)
+		writel(1 << FORCE_FULL_SPEED_MODE, &dev->usb->xcvrdiag);
+
 	/* ... then enable host detection and ep0; and we're ready
 	 * for set_configuration as well as eventual disconnect.
 	 */
@@ -1957,6 +1965,10 @@ static int net2280_stop(struct usb_gadget *_gadget,
 	dev->driver = NULL;
 
 	net2280_led_active (dev, 0);
+
+	/* Disable full-speed test mode */
+	writel(0, &dev->usb->xcvrdiag);
+
 	device_remove_file (&dev->pdev->dev, &dev_attr_function);
 	device_remove_file (&dev->pdev->dev, &dev_attr_queues);
 
@@ -2841,6 +2853,9 @@ static void net2280_shutdown (struct pci_dev *pdev)
 
 	/* disable the pullup so the host will think we're gone */
 	writel (0, &dev->usb->usbctl);
+
+	/* Disable full-speed test mode */
+	writel(0, &dev->usb->xcvrdiag);
 }