[U-Boot-Users] Question about U-Boot in general and the AT91RM9200 in particular
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.
Regards, Javier Ruere
[1] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/25551/focus=25596 [2] http://www.denx.de/wiki/view/DULG/CanUBootBeConfiguredSuchThatItCanBeStarted... [3] http://www.atmel.com/dyn/resources/prod_documents/UBootFlashProgramming.zip [4] http://www.at91.com/www/phpBB2_mirror/viewtopic.php4?t=1300&highlight=at...
In message 200701031949.26084.javierruere@apexar.com you wrote:
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
No, this is NOT correct. If you have NOR flash on your board (which we consider a standard configuration) then U-Boot can boot directly, without a primary bootstrap loader. This is the mode of operation you want to have if your task is to get new hardware running.
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?
If "flash memory" means NOR flash, then yes, this will work fine. Actually this is the recommended (by me) mode of operation.
Best regards,
Wolfgang Denk
Javier Ruere ha scritto:
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.
Regards, Javier Ruere
[1] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/25551/focus=25596 [2] http://www.denx.de/wiki/view/DULG/CanUBootBeConfiguredSuchThatItCanBeStarted... [3] http://www.atmel.com/dyn/resources/prod_documents/UBootFlashProgramming.zip [4] http://www.at91.com/www/phpBB2_mirror/viewtopic.php4?t=1300&highlight=at...
If you have a NOR flash romboot (boot.bin) is no longer necessary, maybe this link could help as well :-)
http://www.koansoftware.com/en/art.php?art=80
Ciao
participants (3)
-
Javier Ruere -
Marco Cavallini -
Wolfgang Denk