Bluetooth: btusb: fix bt fiwmare downloading failure issue for qca bt…

…soc.

[ Upstream commit 4f00bfb ]

This is btsoc timing issue, after host start to downloading bt firmware,
ep2 need time to switch from function acl to function dfu, so host add
20ms delay as workaround.

Signed-off-by: Tim Jiang <tjiang@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/bluetooth/btusb.c

@@ -3558,6 +3558,11 @@ static int btusb_setup_qca_download_fw(struct hci_dev *hdev,
 	sent += size;
 	count -= size;
 
+	/* ep2 need time to switch from function acl to function dfu,
+	 * so we add 20ms delay here.
+	 */
+	msleep(20);
+
 	while (count) {
 		size = min_t(size_t, count, QCA_DFU_PACKET_LEN);