The factory default uboot installed on the nand cannot do ext4load or ext4ls.

To recreate

Plug in sd card with ext4 partition.
Toggle boot_sel switch to boot from nand.
When uboot gives a prompt to press any key. press one.

Then run

ext4ls mmc 0:1

Hangs.

Andy reported it. Zubair and James Cowgill have tested their boards. Same issue. With ext4load too.

ext4load/ext4ls works when uboot is made with make ci20_mmc config.