Запускаю так :
U-Boot> tftpboot 21000000 uImage
macb0: Starting autonegotiation...
macb0: Autonegotiation complete
macb0: link up, 100Mbps full-duplex (lpa: 0x45e1)
Using macb0 device
TFTP from server 192.168.1.209; our IP address is 192.168.1.210
Filename 'uImage'.
Load address: 0x21000000
Loading: #################################################################
####################
done
Bytes transferred = 1243512 (12f978 hex)
U-Boot> bootm 21000000
## Booting kernel from Legacy Image at 21000000 ...
Image Name: Linux-2.6.31.13
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1243448 Bytes = 1.2 MiB
Load Address: 20008000
Entry Point: 20008000
Verifying Checksum ... OK
Loading Kernel Image ... OK
OK
Starting kernel ...
Uncompressing Linux................................................................................ done, booting the kernel.
И всё
Кто чёнибуть подскажет U-Boot собирал сам.