VGE_CDTXADDR
CSR_WRITE_4(sc, VGE_TXDESC_HIADDR, VGE_ADDR_HI(VGE_CDTXADDR(sc, 0)));
CSR_WRITE_4(sc, VGE_TXDESC_ADDR_LO0, VGE_ADDR_LO(VGE_CDTXADDR(sc, 0)));