UATP_ENABLED
KASSERT((sc->sc_status & UATP_ENABLED) == 0);
if (sc->sc_status & UATP_ENABLED) {
sc->sc_status |= UATP_ENABLED;
if (!(sc->sc_status & UATP_ENABLED)) {
sc->sc_status &=~ UATP_ENABLED;