DMAC_PRIORITY_NORMAL
dmac_start(sc, DMAC_PRIORITY_NORMAL);
dmac_free_channel(sc, DMAC_PRIORITY_NORMAL, i);
ds->ds_xfer.dxs_priority = DMAC_PRIORITY_NORMAL;
dx->dx_priority = DMAC_PRIORITY_NORMAL;
sc->sc_rxdx->dx_priority = DMAC_PRIORITY_NORMAL;
sc->sc_txdx->dx_priority = DMAC_PRIORITY_NORMAL;