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

[PHIL.EDWORTHY at renesas.com]

Hi Matthias,

> >> 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.

Thanks for the additional info - SH is a little different then!

Phil