Bluetooth: btusb: fix up firmware download sequence

Data RAM on the device have to be powered on before starting to download
the firmware.

Fixes: a1c49c43 ("Bluetooth: btusb: Add protocol support for MediaTek MT7668U USB devices")
Co-developed-by: Mark Chen <Mark-YW.Chen@mediatek.com>
Signed-off-by: Mark Chen <Mark-YW.Chen@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/btusb.c

@@ -2934,7 +2934,7 @@ static int btusb_mtk_setup_firmware(struct hci_dev *hdev, const char *fwname)
 	const u8 *fw_ptr;
 	size_t fw_size;
 	int err, dlen;
-	u8 flag;
+	u8 flag, param;
 
 	err = request_firmware(&fw, fwname, &hdev->dev);
 	if (err < 0) {
@@ -2942,6 +2942,20 @@ static int btusb_mtk_setup_firmware(struct hci_dev *hdev, const char *fwname)
 		return err;
 	}
 
+	/* Power on data RAM the firmware relies on. */
+	param = 1;
+	wmt_params.op = BTMTK_WMT_FUNC_CTRL;
+	wmt_params.flag = 3;
+	wmt_params.dlen = sizeof(param);
+	wmt_params.data = &param;
+	wmt_params.status = NULL;
+
+	err = btusb_mtk_hci_wmt_sync(hdev, &wmt_params);
+	if (err < 0) {
+		bt_dev_err(hdev, "Failed to power on data RAM (%d)", err);
+		return err;
+	}
+
 	fw_ptr = fw->data;
 	fw_size = fw->size;