Bluetooth: btusb: fix Realtek suspend/resume

Realtek btusb devices don't currently work after suspend/resume because
the updated firmware is quietly lost - the USB hub doesn't notice any
status change upon resume, but some kind of reset has definitely
happened as the LMP subversion has reverted to its original value.

Set the reset_resume flag to trigger probe and upload the new firmware
again.

Like the vendor code, I assume this is not needed when the device is
selected as a wakeup source and hence will retain power during suspend.
On the 2 products I have to hand, when trying this configuration the
hardware seems unable to keep the device powered up during suspend.
The USB hub then detects a status change on resume and does a reset,
so we do not end up in broken state.
Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/btusb.c

@@ -328,6 +328,7 @@ static const struct usb_device_id blacklist_table[] = {
 #define BTUSB_FIRMWARE_LOADED	7
 #define BTUSB_FIRMWARE_FAILED	8
 #define BTUSB_BOOTING		9
+#define BTUSB_RESET_RESUME	10
 
 struct btusb_data {
 	struct hci_dev       *hdev;
@@ -2767,8 +2768,15 @@ static int btusb_probe(struct usb_interface *intf,
 	}
 
 #ifdef CONFIG_BT_HCIBTUSB_RTL
-	if (id->driver_info & BTUSB_REALTEK)
+	if (id->driver_info & BTUSB_REALTEK) {
 		hdev->setup = btrtl_setup_realtek;
+
+		/* Realtek devices lose their updated firmware over suspend,
+		 * but the USB hub doesn't notice any status change.
+		 * Explicitly request a device reset on resume.
+		 */
+		set_bit(BTUSB_RESET_RESUME, &data->flags);
+	}
 #endif
 
 	if (id->driver_info & BTUSB_AMP) {
@@ -2901,6 +2909,14 @@ static int btusb_suspend(struct usb_interface *intf, pm_message_t message)
 	btusb_stop_traffic(data);
 	usb_kill_anchored_urbs(&data->tx_anchor);
 
+	/* Optionally request a device reset on resume, but only when
+	 * wakeups are disabled. If wakeups are enabled we assume the
+	 * device will stay powered up throughout suspend.
+	 */
+	if (test_bit(BTUSB_RESET_RESUME, &data->flags) &&
+	    !device_may_wakeup(&data->udev->dev))
+		data->udev->reset_resume = 1;
+
 	return 0;
 }