Bluetooth: Add new HCI_QUIRK_NO_SUSPEND_NOTIFIER quirk

Some devices, e.g. the RTL8723BS bluetooth part, some USB attached devices,
completely drop from the bus on a system-suspend. These devices will
have their driver unbound and rebound on resume (when the dropping of
the bus gets detected) and will show up as a new HCI after resume.

These devices do not benefit from the suspend / resume handling work done
by the hci_suspend_notifier. At best this unnecessarily adds some time to
the suspend/resume time. But this may also actually cause problems, if the
code doing the driver unbinding runs after the pm-notifier then the
hci_suspend_notifier code will try to talk to a device which is now in
an uninitialized state.

This commit adds a new HCI_QUIRK_NO_SUSPEND_NOTIFIER quirk which allows
drivers to opt-out of the hci_suspend_notifier when they know beforehand
that their device will be fully re-initialized / reprobed on resume.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/hci.h

@@ -238,6 +238,14 @@ enum {
 	 * during the hdev->setup vendor callback.
 	 */
 	HCI_QUIRK_BROKEN_ERR_DATA_REPORTING,
+
+	/*
+	 * When this quirk is set, then the hci_suspend_notifier is not
+	 * registered. This is intended for devices which drop completely
+	 * from the bus on system-suspend and which will show up as a new
+	 * HCI after resume.
+	 */
+	HCI_QUIRK_NO_SUSPEND_NOTIFIER,
 };
 
 /* HCI device flags */

net/bluetooth/hci_core.c

@@ -3940,10 +3940,12 @@ int hci_register_dev(struct hci_dev *hdev)
 	hci_sock_dev_event(hdev, HCI_DEV_REG);
 	hci_dev_hold(hdev);
 
-	hdev->suspend_notifier.notifier_call = hci_suspend_notifier;
-	error = register_pm_notifier(&hdev->suspend_notifier);
-	if (error)
-		goto err_wqueue;
+	if (!test_bit(HCI_QUIRK_NO_SUSPEND_NOTIFIER, &hdev->quirks)) {
+		hdev->suspend_notifier.notifier_call = hci_suspend_notifier;
+		error = register_pm_notifier(&hdev->suspend_notifier);
+		if (error)
+			goto err_wqueue;
+	}
 
 	queue_work(hdev->req_workqueue, &hdev->power_on);
 
@@ -3978,9 +3980,11 @@ void hci_unregister_dev(struct hci_dev *hdev)
 
 	cancel_work_sync(&hdev->power_on);
 
-	hci_suspend_clear_tasks(hdev);
-	unregister_pm_notifier(&hdev->suspend_notifier);
-	cancel_work_sync(&hdev->suspend_prepare);
+	if (!test_bit(HCI_QUIRK_NO_SUSPEND_NOTIFIER, &hdev->quirks)) {
+		hci_suspend_clear_tasks(hdev);
+		unregister_pm_notifier(&hdev->suspend_notifier);
+		cancel_work_sync(&hdev->suspend_prepare);
+	}
 
 	hci_dev_do_close(hdev);