about Spansion flash

If the driver can't detect a PHY it's because it's unable to communicate with the PHY over the MDIO interface. This is basically an I2C interface involving the "mdc" and "mdio" pins. I'm not familiar with this gmii_mii_mux module that appears to interact with these signals somehow.

module ddr2_test_top(
    ...
    mdc,
    mdio,
   ...
);
wire mdio_out;
wire mdio_oe;
assign mdio = mdio_oen ? 1'bz : mdio_out;
nios_ddr2    b2v_inst(
    ...
    .mdio_in_to_the_tse_mac(mdio),
    .mdio_out_from_the_tse_mac(mdio_out),
    .mdio_oen_from_the_tse_mac(mdio_oen),
    ...
);