Bluetooth: btusb: mediatek: fix WMT failure during runtime suspend

WMT cmd/event doesn't follow up the generic HCI cmd/event handling, it
needs constantly polling control pipe until the host received the WMT
event, thus, we should require to specifically acquire PM counter on the
USB to prevent the interface from entering auto suspended while WMT
cmd/event in progress.

Fixes: a1c49c43 ("Bluetooth: btusb: Add protocol support for MediaTek MT7668U USB devices")
Co-developed-by: Jing Cai <jing.cai@mediatek.com>
Signed-off-by: Jing Cai <jing.cai@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/bluetooth/btusb.c

@@ -2482,15 +2482,29 @@ static int btusb_mtk_hci_wmt_sync(struct hci_dev *hdev,
 
 	set_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags);
 
+	/* WMT cmd/event doesn't follow up the generic HCI cmd/event handling,
+	 * it needs constantly polling control pipe until the host received the
+	 * WMT event, thus, we should require to specifically acquire PM counter
+	 * on the USB to prevent the interface from entering auto suspended
+	 * while WMT cmd/event in progress.
+	 */
+	err = usb_autopm_get_interface(data->intf);
+	if (err < 0)
+		goto err_free_wc;
+
 	err = __hci_cmd_send(hdev, 0xfc6f, hlen, wc);
 
 	if (err < 0) {
 		clear_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags);
+		usb_autopm_put_interface(data->intf);
 		goto err_free_wc;
 	}
 
 	/* Submit control IN URB on demand to process the WMT event */
 	err = btusb_mtk_submit_wmt_recv_urb(hdev);
+
+	usb_autopm_put_interface(data->intf);
+
 	if (err < 0)
 		goto err_free_wc;