dxs_priority
dmac_free_channel(sc, DMAC_PRI(dxs->dxs_priority), channel);
rv = 1u << DMAC_PRI(dxs->dxs_priority);
&sc->sc_queue[DMAC_PRI(dxs->dxs_priority)];
&sc->sc_queue[DMAC_PRI(dxs->dxs_priority)], dxs,
ds->ds_xfer.dxs_priority = DMAC_PRIORITY_NORMAL;
dxs->dxs_queue = &sc->sc_queue[DMAC_PRI(dxs->dxs_priority)];
dmac_start(sc, DMAC_PRI(dxs->dxs_priority));
dmac_free_channel(sc, DMAC_PRI(dxs->dxs_priority),
dxs->dxs_queue = &sc->sc_queue[DMAC_PRI(dxs->dxs_priority)];
dmac_start(sc, DMAC_PRI(dxs->dxs_priority));