[Bluetooth] Always use two ISOC URB's

This patch modifies the USB Bluetooth driver to use two ISOC URB's
per RX and TX transfer paths. This is needed for in time transfer
of SCO audio packets over HCI.

drivers/bluetooth/hci_usb.c

@@ -303,6 +303,7 @@ static int hci_usb_open(struct hci_dev *hdev)
 
 #ifdef CONFIG_BT_USB_SCO
 		if (husb->isoc_iface)
+			for (i = 0; i < HCI_MAX_ISOC_RX; i++)
 				hci_usb_isoc_rx_submit(husb);
 #endif
 	} else {
@@ -520,7 +521,7 @@ static void hci_usb_tx_process(struct hci_usb *husb)
 #ifdef CONFIG_BT_USB_SCO
 		/* Process SCO queue */
 		q = __transmit_q(husb, HCI_SCODATA_PKT);
-		if (!atomic_read(__pending_tx(husb, HCI_SCODATA_PKT)) &&
+		if (atomic_read(__pending_tx(husb, HCI_SCODATA_PKT)) < HCI_MAX_ISOC_TX &&
 				(skb = skb_dequeue(q))) {
 			if (hci_usb_send_isoc(husb, skb) < 0)
 				skb_queue_head(q, skb);
@@ -828,7 +829,7 @@ int hci_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
 
 #ifdef CONFIG_BT_USB_SCO
 				case USB_ENDPOINT_XFER_ISOC:
-					if (ep->desc.wMaxPacketSize < size)
+					if (ep->desc.wMaxPacketSize < size || a > 2)
 						break;
 					size = ep->desc.wMaxPacketSize;
 

drivers/bluetooth/hci_usb.h

@@ -41,6 +41,9 @@
 #define HCI_MAX_BULK_TX     	4
 #define HCI_MAX_BULK_RX     	1
 
+#define HCI_MAX_ISOC_RX		2
+#define HCI_MAX_ISOC_TX		2
+
 #define HCI_MAX_ISOC_FRAMES     10
 
 struct _urb_queue {