Marius,
I will have a AT91RM9200 based board real soon now. But apparently the eval board AT91RM9200DK uses a different approach. They have a separate urloader to decompress and copy an U-Boot image into RAM and then jump there...
Actually this "urloader" is called Thunderboot and is a ripped version of ARMboot (a practice which seems to be quite fashionable these days.) I never got round to asking them for the sources, nor do I understand why they concealed it so pathetically :-) The flash images even contain references to ARMboot. Maybe you want to have a go at them?
Ehm. Nope. That's not what I meant. They replace Thunderboot by their so called "AT91RM9200-Boot". Then they build a U-Boot version for the eval board AT91RM9200DK and gzip it. The AT91RM9200-Boot and the zipped version of AT91RM9200-U-Boot are stored in flash. Now all that AT91RM9200-Boot does when power-on is init the hardware (especially SDRAM), decompress u-boot.gz into SDRAM and jump to it.
Atmel said:
"We chose, to put a compressed boot due to memory mapping constraints. We need to keep a sector for environment variables the 8Kbyte-size sector is enough."
IMHO this wasn't nessesary at all since they do seem to have flash with a few small sectors. But nevermind.
They even provide a "AT91RM9200-Loader" which could be used to download the above files via the DEBUG UNIT (DBGU).
I got these sources from Atmel. Now that I have these source I hope I can get this working on my board as well. Then when this two-(or three)-step version works I want to make U-Boot working like for all the other plattforms: init SDRAM, relocate and start.
Ok?
Steven