Bluetooth: hci_sync: Fix suspending with wrong filter policy

When suspending the scan filter policy cannot be 0x00 (no acceptlist)
since that means the host has to process every advertisement report
waking up the system, so this attempts to check if hdev is marked as
suspended and if the resulting filter policy would be 0x00 (no
acceptlist) then skip passive scanning if thre no devices in the
acceptlist otherwise reset the filter policy to 0x01 so the acceptlist
is used since the devices programmed there can still wakeup be system.

Fixes: 182ee45d ("Bluetooth: hci_sync: Rework hci_suspend_notifier")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

net/bluetooth/hci_sync.c

@@ -2976,6 +2976,27 @@ static int hci_passive_scan_sync(struct hci_dev *hdev)
 	 */
 	filter_policy = hci_update_accept_list_sync(hdev);
 
+	/* If suspended and filter_policy set to 0x00 (no acceptlist) then
+	 * passive scanning cannot be started since that would require the host
+	 * to be woken up to process the reports.
+	 */
+	if (hdev->suspended && !filter_policy) {
+		/* Check if accept list is empty then there is no need to scan
+		 * while suspended.
+		 */
+		if (list_empty(&hdev->le_accept_list))
+			return 0;
+
+		/* If there are devices is the accept_list that means some
+		 * devices could not be programmed which in non-suspended case
+		 * means filter_policy needs to be set to 0x00 so the host needs
+		 * to filter, but since this is treating suspended case we
+		 * can ignore device needing host to filter to allow devices in
+		 * the acceptlist to be able to wakeup the system.
+		 */
+		filter_policy = 0x01;
+	}
+
 	/* When the controller is using random resolvable addresses and
 	 * with that having LE privacy enabled, then controllers with
 	 * Extended Scanner Filter Policies support can now enable support