NGE_TBI_BMCR
CSR_WRITE_4(sc, NGE_TBI_BMCR, NGE_TBIBMCR_ENABLE_ANEG
CSR_WRITE_4(sc, NGE_TBI_BMCR, NGE_TBIBMCR_ENABLE_ANEG);
CSR_WRITE_4(sc, NGE_TBI_BMCR, 0);
CSR_WRITE_4(sc, NGE_TBI_BMCR, 0);
if (CSR_READ_4(sc, NGE_TBI_BMCR) & NGE_TBIBMCR_LOOPBACK)