[U-Boot-Users] Question about U-Boot in general and the AT91RM9200 in particular

Javier Ruere javierruere at apexar.com
Wed Jan 3 23:49:25 CET 2007

Hello everyone,
	I have been working with an AT91RM9200-EK board for a couple of months now 
and we are about to make our own custom board. Lately I started investigating 
about U-Boot and how it works in this board and, though I have found a lot of 
bits of information, I am still quite confused.
	I would like to ask about U-Boot running from RAM. On the one hand, I have 
seen links [1] and [2] that say that it should not be done but, on the other 
hand, from the documentation from Atmel [3] I see it _is_ being run from RAM. 
I have done this myself with u-boot 1.1.6 defining CONFIG_SKIP_LOWLEVEL_INIT 
at the top of include/configs/at91rm9200dk.h, otherwise it wouldn't work. I 
found out about this define here [4]
	For what I gather from the instructions from Atmel, there is always a 
bootloader before U-Boot, loading it from the dataflash, serial port or Flash 
and this could explain why I must define CONFIG_SKIP_LOWLEVEL_INIT, so that 
the hardware is not initialized twice.
	Would it work to put an uncompressed image of U-Boot at the beginning of the 
flash memory and let it initialize the board if I don't add the define I 
mentioned before?
	Thank you all for your time and help.

		Javier Ruere

[1] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/25551/focus=25596

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