The following guide comes from AM1808/OMAP-L138 SOM-M1 SPI Flash Recovery Application Note 556 
NOTE: Some of our guides instruct you to erase and reprogram the SPI flash without reprogramming the MAC address. We are updating these documents with the appropriate instructions. In the meantime use the instructions in this guide.
The Ethernet MAC address of your SOM-M1 can be found on the white sticker attached to the
module with the format 00:08:EE:XX:XX:XX. Erasing the SPI flash with the Flash Loading Utility
as described in this document will also erase this MAC address in the SOM-M1. This section will
provide the steps to restore the MAC address.
1. Boot the development kit to the U-Boot prompt and enter the commands below. NOTE: The
example MAC address 00:08:EE:03:5B:40 is used below. Be sure to replace this address
with values appropriate for your system.
U-Boot > mm.b c0000000
c0000000: 00 ? 00
c0000001: 10 ? 08
c0000002: 08 ? EE
c0000003: 01 ? 03
c0000004: 40 ? 5B
c0000005: 21 ? 40
c0000006: 0c ? q
U-Boot > md.b c0000000
c0000000: 00 08 EE 03 5B 40 …
U-Boot > sf probe 0
8192 KiB M25P64 at 0:0 is now current device
U-Boot> sf write c0000000 7f0000 6
The original MAC address should now be restored to the SOM-M1.
2. Reboot the system and enter the command below to verify ethaddr is set correctly.
U-Boot > printenv
bootargs=mem=32M console=ttyS2,115200n8 root=/dev/ram0 rw
bootcmd=sf probe 0;sf read 0xc0700000 0x80000 0x200000;sf read
0xc1180000 0x280000 0x300000;bootm 0xc0700000
ver=U-Boot 2009.01 (Sep 17 2009 - 17:41:56)
3. Test that the Ethernet works as expected by pinging another system on the network.
a. Connect an Ethernet cable between your development kit and the network.
b. Set the development kit IP address.
For static IP addresses:
U-Boot > set ipaddr <static ip address>