[U-Boot] Getting U-Boot running on Toradex Colibri T20 on Iris board

Hi,

I'm trying to get the U-Boot running on the Iris board with the Toradex Colibri T20 module. I was able to flash the U-Boot and it starts but then immediately stops with the only message being:

U-Boot 2013.07 (Aug 06 2013 - 17:47:43)

TEGRA20 Board: Toradex Colibri T20 on Iris DRAM:

The Colibri T20 board used is: 256MB RAM V1.2A

Could you please give me any idea what I might be doing wrong?