TXC_BIST_CTL
ef4_mdio_write(efx, mmd, TXC_BIST_CTL, bctl);
ef4_mdio_write(efx, mmd, TXC_BIST_CTL, bctl);
ef4_mdio_write(efx, mmd, TXC_BIST_CTL,
ef4_mdio_write(efx, mmd, TXC_BIST_CTL, bctl);
bctl = ef4_mdio_read(efx, mmd, TXC_BIST_CTL);
ef4_mdio_write(efx, mmd, TXC_BIST_CTL, 0);