[U-Boot] [PATCH 6/6] powerpc: Add LINK_OFF calls in early C-code.

[Graeme Russ]

On Wed, Nov 24, 2010 at 10:24 AM, Scott Wood <scottwood at freescale.com> wrote:
> On Wed, 24 Nov 2010 00:03:13 +0100
> Wolfgang Denk <wd at denx.de> wrote:
>
>> Dear Scott Wood,
>>
>> In message <20101123163204.4f843e61 at udp111988uds.am.freescale.net> you wrote:
>> >
>> > How about playing with BATs before entering C code, so that the image
>> > always appears at the same effective address?
>>
>> Not all systems have BATs.
>
> I was speaking in the context of what he wanted to do with an 83xx board
> -- but the concept applies to any hardware with an MMU that isn't too
> painful to set up that early.
>
> If someone wants to do this kind of thing on hardware that doesn't
> meet that description, that's another matter -- if the the hardware
> doesn't provide a nicer bank switching mechanism (e.g. p4080ds lets you
> rotate the flash banks' physical addresses, rather than change the
> reset vector), or an SRAM that U-Boot (or an SPL) could copy itself to
> before C code, etc.

It seems to me that we are applying at the architecture level a 'nice to
have' which may belong at the board level. How many vendors are going to
do a fancy 'two U-Boot images' trickery? Will it be (nearly) every 83xx
board?

I agree with Scott - If you want to do something that fancy, provide
support for it in your board hardware. I don't like the idea of diverging
the core feature-set available at the architecture level if those features
belong more at the SOC or Board level.

Regards,

Graeme