Prevent a race condition upon resume by adding a supplementary delay.

This is a workaround needed at least by Renesas controllers.  I didn't
find any documentation about this issue and I guess other open source
xHCI implementations do not see this race because they do much more work
upon resume.

Thanks to Remi Locherer for reporting this issue on bugs@.

diff --git a/sys/dev/usb/xhci.c b/sys/dev/usb/xhci.c
index b2f4a3c..f79f4b4 100644 (file)
--- a/sys/dev/usb/xhci.c
+++ b/sys/dev/usb/xhci.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: xhci.c,v 1.51 2015/01/04 20:10:08 mpi Exp $ */
+/* $OpenBSD: xhci.c,v 1.52 2015/01/05 12:38:16 mpi Exp $ */
 
 /*
  * Copyright (c) 2014 Martin Pieuchot
@@ -515,6 +515,10 @@ xhci_activate(struct device *self, int act)
                xhci_reset(sc);
                xhci_ring_reset(sc, &sc->sc_cmd_ring);
                xhci_ring_reset(sc, &sc->sc_evt_ring);
+
+               /* Renesas controllers, at least, need more time to resume. */
+               usb_delay_ms(&sc->sc_bus, USB_RESUME_WAIT);
+
                xhci_config(sc);
 
                sc->sc_bus.use_polling--;