[U-Boot] Working on u-boot on panda board.

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Aneesh V wrote:
> Hi Gilles,
> 
> On Thursday 17 March 2011 06:13 PM, Gilles Chanteperdrix wrote:
>> Hi,
>>
>> I would like to make some changes to u-boot on pandaboard. Sometimes in
>> the past, in u-boot, I could "loadb" a new u-boot binary, then "go" to
>> it, and the new version of u-boot would start. This was far from
>> perfect, but it made testing small changes possible. This also works
>> with the version of u-boot provided on the pandaboard community site.
>>
>> The magic which made this possible was in the "start.S" file, I see that
>> the code changed, but there still seems to be a relocation (somewhat
>> more complicated, since it handles ELF relocations), so it seems it
>> should work.
>>
>> So my question is: is this "loadb+go" method still supposed to be
>> working, and only broken, somehow, on pandaboard? Or is it no longer
>> supposed to be working?
> 
> Couple of things you might want to consider.
> * According to the new relocation scheme u-boot should start running
> from the address that it is linked to. You must load it to
> CONFIG_SYS_TEXT_BASE

You mean the address where u-boot is currently loaded? But that will not
work, right? I mean, it would override the current u-boot while it is
currently running.

I do not really understand this answer, what does it mean? The
relocation code does not work if the address it is starting from is not
CONFIG_SYS_TEXT_BASE? What if I reinsert the memcpy in start.S which
copies to CONFIG_SYS_TEXT_BASE?

> * Data cache enabled in U-Boot could be a problem. You will end up
> having cache coherency issues unless you flush the caches after loadb.
> Better keep them disabled using CONFIG_SYS_NO_DCACHE

Ok, that is not really an issue for development.

-- 
					    Gilles.