MediaTek claim an special usb intr interface for ISO data transmission.
The interface need to be released before unregistering hci device when
usb disconnect. Removing BT usb dongle without properly releasing the
interface may cause Kernel panic while unregister hci device.

Signed-off-by: Chris Lu <chris.lu@mediatek.com>
---
 drivers/bluetooth/btusb.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index dfc42bdc8aaf..a434aefe68f2 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -2614,9 +2614,9 @@ static void btusb_mtk_claim_iso_intf(struct btusb_data *data)
 	set_bit(BTMTK_ISOPKT_OVER_INTR, &btmtk_data->flags);
 }
 
-static void btusb_mtk_release_iso_intf(struct btusb_data *data)
+static void btusb_mtk_release_iso_intf(struct hci_dev *hdev)
 {
-	struct btmtk_data *btmtk_data = hci_get_priv(data->hdev);
+	struct btmtk_data *btmtk_data = hci_get_priv(hdev);
 
 	if (btmtk_data->isopkt_intf) {
 		usb_kill_anchored_urbs(&btmtk_data->isopkt_anchor);
@@ -2632,6 +2632,16 @@ static void btusb_mtk_release_iso_intf(struct btusb_data *data)
 	clear_bit(BTMTK_ISOPKT_OVER_INTR, &btmtk_data->flags);
 }
 
+static int btusb_mtk_disconnect(struct hci_dev *hdev)
+{
+	/* This function describes the specific additional steps taken by MediaTek
+	 * when Bluetooth usb driver's resume function is called.
+	 */
+	btusb_mtk_release_iso_intf(hdev);
+
+	return 0;
+}
+
 static int btusb_mtk_reset(struct hci_dev *hdev, void *rst_data)
 {
 	struct btusb_data *data = hci_get_drvdata(hdev);
@@ -2649,7 +2659,7 @@ static int btusb_mtk_reset(struct hci_dev *hdev, void *rst_data)
 		return err;
 
 	if (test_bit(BTMTK_ISOPKT_RUNNING, &btmtk_data->flags))
-		btusb_mtk_release_iso_intf(data);
+		btusb_mtk_release_iso_intf(hdev);
 
 	btusb_stop_traffic(data);
 	usb_kill_anchored_urbs(&data->tx_anchor);
@@ -2703,14 +2713,13 @@ static int btusb_mtk_setup(struct hci_dev *hdev)
 
 static int btusb_mtk_shutdown(struct hci_dev *hdev)
 {
-	struct btusb_data *data = hci_get_drvdata(hdev);
 	struct btmtk_data *btmtk_data = hci_get_priv(hdev);
 	int ret;
 
 	ret = btmtk_usb_shutdown(hdev);
 
 	if (test_bit(BTMTK_ISOPKT_RUNNING, &btmtk_data->flags))
-		btusb_mtk_release_iso_intf(data);
+		btusb_mtk_release_iso_intf(hdev);
 
 	return ret;
 }
@@ -3824,6 +3833,7 @@ static int btusb_probe(struct usb_interface *intf,
 		data->recv_acl = btmtk_usb_recv_acl;
 		data->suspend = btmtk_usb_suspend;
 		data->resume = btmtk_usb_resume;
+		data->disconnect = btusb_mtk_disconnect;
 	}
 
 	if (id->driver_info & BTUSB_SWAVE) {
-- 
2.18.0