[U-Boot] uboot redundancy.

[Graeme Russ <graeme.russ@gmail.com>]

On 10/07/10 00:03, Sagar Heroorkar wrote:
> Hi All,
> 
> I am planning to implement uboot redundancy.
> This means having the following idea which we thought.
> 
> Golden-Uboot which is flashed in the NOR-FLASH. This is not field
> upgradable.
> This golden uboot is going to have logic to pick the other uboot based on
> certain flags or env vriables
> 
> As i mentioned i wanted the uboot to be redundant.
> So i will have 2 copies of uboot now.
> Uboot1
> Uboot2

I have a similar plan for x86 although the rationale was to enable rapid
load-reset-test(-write to boot ROM on pass).

The x86 port has the ability to load a new version of U-Boot into an
arbitrary location in RAM and 'boot-strap' directly into it. I was planning
on doing something similar to what you propose - All that is needed is a
little bit of code in the low-level boot-strap to choose whether to
continue loading the main image, or a secondary image. Note that at this
point, there is no environment and no CFI driver so any decision would need
to be based on NVRAM data.

> 
> Golden uboot will pick either of one uboots mentioned above. If the uboot1
> which is picked fails to boot, then we will have uboot2 as back up to boot.
> vice versa.
> 
> Golden uboot recides in the address fffa0000 (start.s).
> There is a relocation code which copies the code from flash to ram. if the
> uboot which i have picked addressess will change , hence how can i do the
> relocation?

x86 port has 'proper' relocation. It does not matter where the target image
resides, it will reload itself into the highest available memory location
and run from there.

> 
> Any pointers will help me if any one already did this kind of approach
> making uboot redundant.
> 

There were some posts a little while ago (search for posts by Joakim
Tjernlund - he was working on a 100% position independent U-Boot)

My work on U-Boot has been very slow of late, but I would be really
interested in working through this idea in a platform independent way.

--
Graeme