[…]Here is where I see a dilemma with using U-Boot for test. First I have to build U-Boot, and second have enough of the system operational, DDR (DDR controller/PHY) and SD flash interface etc. before testing can begin. Testing often involves non-operational system or minimally functionally operational hardware. The use of U-Boot expects a significant portion of the target hardware operational.
Second, assuming that you were successful in building U-Boot you now need to load it on the flash of the UUT. Be sure to follow the below warning. If U-Boot is already installed and running on your board, you can use these instructions to download another U-Boot image to replace the current one.
Warning: Before you can install the new image, you must erase the current one. If anything goes wrong your board will be dead. It is strongly recommended that you have a backup of the old, working U-Boot image or you know how to install an image on a virgin system.
Next U-Boot has limited testing capabilities.[…]
Firmware Security 