[U-Boot-Users] U-Boot for AT91RM9200DK

[Steven Scholz]

Hi Rick et al.,

as I mentioned before U-Boot is running on our AT91RM9200 based board. I went 
down the path ATMEL was suggesting. They use this memory map on their eval board 
AT91RM9200DK:

24k	Boot Image
32KB	free
8KB	Environment
64KB	gzipped U-Boot image

The "Boot image" is a small (11k) piece of code which initialises clocks, flash, 
SDRAM and serial port. Then it decompresses the "gzipped U-Boot image" into 
SDRAM and jumps to it. The reason for that seems to be:

 > 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.

They probably overlooked that you could embedded the environment into U-Boot. By 
using a correct u-boot.lds linker file one can reserve an 8Kbyte-size sector in 
the middle of U-Boot. So instead one could use this memory map:

56KB	U-Boot
8KB	Environment
64KB	U-Boot

using the same 128KB of flash.

Since the CPU was setup by the bootloader there's no init and relocation code 
for the AT91RM9200 in U-Boot (yet).

So I spend a day, "wrote" some init and relocation code and now U-Boot is 
starting directly from flash and relocates itself to RAM. No Preboot needed. Nor 
gzipped image of U-Boot.

I would like to change the official U-Boot code for the AT91RM9200 and 
AT91RM9200DK so that it can be used without the need of another bootloader.
This way it would be a lot easier for people to port U-Boot to their hardware.

What do you think?
Anyone interessted?

I'd love to hear suggestion, where to put specific parts of the init code. Other 
ARM cpus use a board specific memsetup.S file.
For an AT91RM9200 we have to setup more than just the SDRAM.
Should we put all the init code into cpu/at91rm9200/{start.S} and use CONFIG_ 
and CFG_?
Or should every AT91 based board copy the same code again and again into thier 
own subdirectory?

Looking forward to your ideas!

Thanks. And sorry for the long mail!

-- 
Steven Scholz

imc Measurement & Control               imc Meßsysteme GmbH
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