cdc_ncm: toggle altsetting to force reset before setup

[ Upstream commit 48906f62 ]

Some devices will silently fail setup unless they are reset first.
This is necessary even if the data interface is already in
altsetting 0, which it will be when the device is probed for the
first time.  Briefly toggling the altsetting forces a function
reset regardless of the initial state.

This fixes a setup problem observed on a number of Huawei devices,
appearing to operate in NTB-32 mode even if we explicitly set them
to NTB-16 mode.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: hard-code 1 for data_altsetting]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/usb/cdc_ncm.c

@@ -550,7 +550,11 @@ static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
 
 	iface_no = ctx->data->cur_altsetting->desc.bInterfaceNumber;
 
-	/* reset data interface */
+	/* Reset data interface. Some devices will not reset properly
+	 * unless they are configured first.  Toggle the altsetting to
+	 * force a reset
+	 */
+	usb_set_interface(dev->udev, iface_no, 1);
 	temp = usb_set_interface(dev->udev, iface_no, 0);
 	if (temp)
 		goto error2;