GMAC_TXMACCONFIG
x = gmac_read_reg(sc, GMAC_TXMACCONFIG);
gmac_write_reg(sc, GMAC_TXMACCONFIG, x);
x = gmac_read_reg(sc, GMAC_TXMACCONFIG);
gmac_write_reg(sc, GMAC_TXMACCONFIG, x);
gmac_write_reg(sc, GMAC_TXMACCONFIG, 6);
gmac_write_reg(sc, GMAC_TXMACCONFIG, 0);
gmac_write_reg(sc, GMAC_TXMACCONFIG, 6);
gmac_write_reg(sc, GMAC_TXMACCONFIG, 0);