PDC_RNPR
bus_space_write_4(iot, ioh, offset + PDC_RNPR, fifo->f_buf_addr + fifo->f_pdc_wr_ndx);
bus_space_write_4(iot, ioh, offset + PDC_RNPR, fifo->f_buf_addr);
PUTREG(sc, SPI_PDC_BASE + PDC_RNPR, sc->sc_dmaaddr + sc->sc_dmaoffs);