VGE_RXCFG
CSR_CLRBIT_1(sc, VGE_RXCFG, VGE_RXCFG_FIFO_THR|VGE_RXCFG_VTAGOPT);
CSR_SETBIT_1(sc, VGE_RXCFG, VGE_RXFIFOTHR_128BYTES);
cfg = CSR_READ_1(sc, VGE_RXCFG);
CSR_WRITE_1(sc, VGE_RXCFG, cfg);