We use a RMII in our hardware iMX6 design. We don't have a PHY with EEPROM to store MAC address and we read it from SPI-FLASH in uboot program.
We notice that if we want to transmit MAC address to fec_main.c part of freescale ethernet driver we need to declare “fec_mac=<mac address value>” in bootargs parameters to have a good management. ‘iMX6 SABRE-SD Linux Release Notes’ document and comment in fec_main.c contain some mistake about this point.
I hope this feedback can be useful for other users.