From: Ajeesh Kumar

We have a custom board with MPC8548E processor, please help me in suggesting/sharing Ethernet Internal/External Loopback testing code piece. Also any Phy level loop back too.

If you have a typical phy and this commit applied, you can use the mii command to put the phy in loopback and ping your own ip.

Something like: => mii r 0 0 1040 => mii w 0 0 5040 # set bit 14 => ping $ipaddr

http://git.denx.de/?p=u-boot.git;a=commit;h=83853178bd36bca6f0f8f1331476 620c84a587fc

-Ed