RTK_RXSTAT_LEN
RTK_RXSTAT_LEN, BUS_DMASYNC_POSTREAD);
RTK_RXSTAT_LEN, BUS_DMASYNC_PREREAD);
rx_bytes += total_len + RTK_RXSTAT_LEN;
cur_rx = (cur_rx + RTK_RXSTAT_LEN) % RTK_RXBUFLEN;