[U-Boot] newbie questions regarding some config options.

[Matthias Weisser <weisserm@arcor.de>]

Am 13.06.2011 15:09, schrieb PHIL.EDWORTHY at renesas.com:
> 
> Hi Christopher,
> 
>> What is the CONFIG_SYS_TEXT_BASE variable and how can
>>  I figure out what it should be?
> 
> U-boot is typically stored in flash and one of the first things it does when executed is relocate to ram. CONFIG_SYS_TEXT_BASE is
the relocation
> address. Typically, u-boot global data, heap and then stack is stored just below this.

On ARM, CONFIG_SYS_TEXT_BASE is typically the base address of the image
in flash. This is, on a system booting from NOR, the address of the
first instruction which is fetched from the CPU.

> Since u-boot is used to load some other program like the kernel, you need the u-boot relocation address to be out of the way of this. So, for the
> boards I have seen (not arm), CONFIG_SYS_TEXT_BASE is set to the top of ram - 256KB, i.e. enough room for the u-boot image.

The relocation address is dynamically calculated from a couple of
(runtime) information and has nothing to do with CONFIG_SYS_TEXT_BASE.
This is true for ARM and AFAIK for PPC.

Matthias