GT_CPU_Master_Ctl
cpumstr = bus_space_read_4(sc->sc_iot, sc->sc_ioh, GT_CPU_Master_Ctl);
bus_space_write_4(sc->sc_iot, sc->sc_ioh, GT_CPU_Master_Ctl, cpumstr);
cpumstr = gt_read(gt, GT_CPU_Master_Ctl);