Q:I want to make u-boot to do something automatically after power up, thinking about I am booting from a serial Flash of limited size, and want to read my kernel stored in the SD card in to RAM and boot it, how?
A: You can achieve this by customize the u-boot environment. type print to show all the envs.
take the current default setting for example, the sequence is like this:
bfin> print bootcmd
bfin> print run ramboot
## Error: "run" not defined
ramboot=tftp $(loadaddr) $(ramfile);run ramargs;run addip;bootm
the bootcmd get automatically runs after boots, fetch the uImage from tftp server, set kernel boot args, and run bootm.
so you can customize the bootcmd, do jobs including reading your flash contents to a RAM location, and bootm this RAM location.