CPSW_CPDMA_TX_CP
tx0_cp = bus_space_read_4(sc->sc_bst, sc->sc_bsh, CPSW_CPDMA_TX_CP(0));
bus_space_write_4(sc->sc_bst, sc->sc_bsh, CPSW_CPDMA_TX_CP(0), 0xfffffffc);
tx0_cp = bus_space_read_4(sc->sc_bst, sc->sc_bsh, CPSW_CPDMA_TX_CP(0));
bus_space_write_4(sc->sc_bst, sc->sc_bsh, CPSW_CPDMA_TX_CP(0),
stat = bus_space_read_4(sc->sc_bst, sc->sc_bsh, CPSW_CPDMA_TX_CP(0));
bus_space_write_4(sc->sc_bst, sc->sc_bsh, CPSW_CPDMA_TX_CP(i), 0);