-----Original Message----- From: u-boot-users-admin@lists.sourceforge.net [mailto:u-boot-users-admin@lists.sourceforge.net]On Behalf Of Kerl, John Sent: Wednesday, January 14, 2004 4:46 PM To: 'u-boot-users@lists.sourceforge.net' Subject: [U-Boot-Users] Running U-Boot as a standalone application

Hello:

Another newbie question, I'm afraid ...

What I am trying to do is run another copy of U-Boot from SRAM, i.e. treating U-Boot #2 as a standalone application to be loaded by U-Boot #1. This way I don't have to overwrite the boot code stored in the flash.

[snip]

which is a machine check in PITException. I can and will debug this further, but I wonder if some things are already known. Namely:

• What I'm doing is re-running all the init code. This is overkill, since the CPU has already been initialized, but it is easiest to code, since I just need to modify the .lds et al.

• The other extreme would be to re-run none of the init code (except installing handlers, etc.), which I don't mind doing except that it sounds like a several-day project.

• Is there a happy medium?

• There is a __DEBUG_START_FROM_SRAM__ macro which I see in the code, but it doesn't appear to be used very many places.

• I think someone else out there must have tried something similar before ... however, if there's something in the U-Boot manual on this topic, I've missed it.

Thanks for any and all info, and for your patience. :)

This is a FAQ. People have successfully run out of RAM, but doing that is discouraged since you have to have as much or more very low level knowledge as running out of flash. Portions of the re-init are Bad, Real Bad to run twice. RAM init is the obvious one, and there may be more.

Bullet #1 won't work (which you proved once more).

As you pointed out in your second bullet, hacking up the init code is a multiple day project. In the same amount of time, you should be up and running out of flash, so why bother (paraphrasing Wolfgang here :-).

If you wish to run out of RAM you are welcome to do so, but about all the advice you will get is "don't do that."

gvb P.S. Don't do that. There, I said it first ;-)

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