diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index a26ff28..b59971c 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -170,6 +170,15 @@
 	 * during the hdev->setup vendor callback.
 	 */
 	HCI_QUIRK_SIMULTANEOUS_DISCOVERY,
+
+	/* When this quirk is set, the enabling of diagnostic mode is
+	 * not persistent over HCI Reset. Every time the controller
+	 * is brought up it needs to be reprogrammed.
+	 *
+	 * This quirk can be set before hci_register_dev is called or
+	 * during the hdev->setup vendor callback.
+	 */
+	HCI_QUIRK_NON_PERSISTENT_DIAG,
 };
 
 /* HCI device flags */
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index b36a2e5..f332680 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -162,6 +162,16 @@
 	if (strtobool(buf, &enable))
 		return -EINVAL;
 
+	/* When the diagnostic flags are not persistent and the transport
+	 * is not active, then there is no need for the vendor callback.
+	 *
+	 * Instead just store the desired value. If needed the setting
+	 * will be programmed when the controller gets powered on.
+	 */
+	if (test_bit(HCI_QUIRK_NON_PERSISTENT_DIAG, &hdev->quirks) &&
+	    !test_bit(HCI_RUNNING, &hdev->flags))
+		goto done;
+
 	hci_req_lock(hdev);
 	err = hdev->set_diag(hdev, enable);
 	hci_req_unlock(hdev);
@@ -169,6 +179,7 @@
 	if (err < 0)
 		return err;
 
+done:
 	if (enable)
 		hci_dev_set_flag(hdev, HCI_VENDOR_DIAG);
 	else
@@ -1494,6 +1505,14 @@
 			ret = __hci_init(hdev);
 	}
 
+	/* If the HCI Reset command is clearing all diagnostic settings,
+	 * then they need to be reprogrammed after the init procedure
+	 * completed.
+	 */
+	if (test_bit(HCI_QUIRK_NON_PERSISTENT_DIAG, &hdev->quirks) &&
+	    hci_dev_test_flag(hdev, HCI_VENDOR_DIAG) && hdev->set_diag)
+		ret = hdev->set_diag(hdev, true);
+
 	clear_bit(HCI_INIT, &hdev->flags);
 
 	if (!ret) {