NET: usb: cdc_mbim: add quirk for supporting Telit LE922A

Telit LE922A MBIM based composition does not work properly
with altsetting toggle done in cdc_ncm_bind_common.

This patch adds CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE quirk
to avoid this procedure that, instead, is mandatory for
other modems.

Signed-off-by: Daniele Palmas <[e-mail]>
Reviewed-by: Bjørn Mork <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/usb/cdc_mbim.c

···
 	.data = CDC_NCM_FLAG_NDP_TO_END,
 };
 
+/* Some modems (e.g. Telit LE922A6) do not work properly with altsetting
+ * toggle done in cdc_ncm_bind_common. CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE
+ * flag is used to avoid this procedure.
+ */
+static const struct driver_info cdc_mbim_info_avoid_altsetting_toggle = {
+	.description = "CDC MBIM",
+	.flags = FLAG_NO_SETINT | FLAG_MULTI_PACKET | FLAG_WWAN,
+	.bind = cdc_mbim_bind,
+	.unbind = cdc_mbim_unbind,
+	.manage_power = cdc_mbim_manage_power,
+	.rx_fixup = cdc_mbim_rx_fixup,
+	.tx_fixup = cdc_mbim_tx_fixup,
+	.data = CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE,
+};
+
 static const struct usb_device_id mbim_devs[] = {
 	/* This duplicate NCM entry is intentional. MBIM devices can
 	 * be disguised as NCM by default, and this is necessary to
···
 	{ USB_VENDOR_AND_INTERFACE_INFO(0x12d1, USB_CLASS_COMM, USB_CDC_SUBCLASS_MBIM, USB_CDC_PROTO_NONE),
 	  .driver_info = (unsigned long)&cdc_mbim_info_ndp_to_end,
 	},
+
+	/* Telit LE922A6 in MBIM composition */
+	{ USB_DEVICE_AND_INTERFACE_INFO(0x1bc7, 0x1041, USB_CLASS_COMM, USB_CDC_SUBCLASS_MBIM, USB_CDC_PROTO_NONE),
+	  .driver_info = (unsigned long)&cdc_mbim_info_avoid_altsetting_toggle,
+	},
+
 	/* default entry */
 	{ USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_MBIM, USB_CDC_PROTO_NONE),
 	  .driver_info = (unsigned long)&cdc_mbim_info_zlp,

drivers/net/usb/cdc_ncm.c

···
 
 	iface_no = ctx->data->cur_altsetting->desc.bInterfaceNumber;
 
+	/* Device-specific flags */
+	ctx->drvflags = drvflags;
+
 	/* Reset data interface. Some devices will not reset properly
 	 * unless they are configured first.  Toggle the altsetting to
-	 * force a reset
+	 * force a reset.
+	 * Some other devices do not work properly with this procedure
+	 * that can be avoided using quirk CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE
 	 */
-	usb_set_interface(dev->udev, iface_no, data_altsetting);
+	if (!(ctx->drvflags & CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE))
+		usb_set_interface(dev->udev, iface_no, data_altsetting);
+
 	temp = usb_set_interface(dev->udev, iface_no, 0);
 	if (temp) {
 		dev_dbg(&intf->dev, "set interface failed\n");
···
 
 	/* finish setting up the device specific data */
 	cdc_ncm_setup(dev);
-
-	/* Device-specific flags */
-	ctx->drvflags = drvflags;
 
 	/* Allocate the delayed NDP if needed. */
 	if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {

include/linux/usb/cdc_ncm.h

···
 #define CDC_NCM_TIMER_INTERVAL_MAX		(U32_MAX / NSEC_PER_USEC)
 
 /* Driver flags */
-#define CDC_NCM_FLAG_NDP_TO_END	0x02		/* NDP is placed at end of frame */
+#define CDC_NCM_FLAG_NDP_TO_END			0x02	/* NDP is placed at end of frame */
+#define CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE	0x04	/* Avoid altsetting toggle during init */
 
 #define cdc_ncm_comm_intf_is_mbim(x)  ((x)->desc.bInterfaceSubClass == USB_CDC_SUBCLASS_MBIM && \
 				       (x)->desc.bInterfaceProtocol == USB_CDC_PROTO_NONE)