If you read the uboot source, you can easily find the mac from fuse is set automatically.
It doesn't matter it is imx8mp-lpddr4-evk or imx8mp-ddr4 board, actually the code is for fec accrossing all i.MX using fec including such as i.MX6, i.MX8M family, etc.
uboot-imx/drivers/net/fec_mxc.c
if (fec_get_hwaddr(fec->dev_id, ethaddr) == 0) {
debug("got MAC%d address from fuse: %pM\n", fec->dev_id, ethaddr);
memcpy(edev->enetaddr, ethaddr, 6);
if (fec->dev_id)
sprintf(mac, "eth%daddr", fec->dev_id);
else
strcpy(mac, "ethaddr");
if (!env_get(mac))
eth_env_set_enetaddr(mac, ethaddr);
}
return ret;
static int fec_get_hwaddr(int dev_id, unsigned char *mac)
{
imx_get_mac_from_fuse(dev_id, mac);
return !is_valid_ethaddr(mac);
}