[U-Boot] UBoot running UBoot - is it possible?

[Simon Goldschmidt]

On 13.11.2018 17:00, Wolfgang Denk wrote:
> Dear Simon,
>
> In message <CAAh8qsxB3YNoDruZnmcPvkygc7HXVOcf=PNdA4xRp=PjmQANsw at mail.gmail.com> you wrote:
>> My idea was to let SPL implement a dedicated boot counter/watchdog
>> that detects problems starting U-Boot and using a backup copy if it
>> fails multiple times. Of course you need an SPL on your board to do
>> this. Plus you end up with the same problem for updating SPL, but I'm
>> lucky here that my platform (socfpga gen5) has redundant storage for
>> SPL and implements a startup watchdog mechanism for the SPL.
> In other words, you are just adding enough additional complexity to
> SPL to make it reasonably likely that there will be bugs that need
> to be fixed later, i. e. you have to update the SPL.
>
> And then?
>
> You are just moving the problem, not solving it.

That's not how I see it. As I see it, I have to implement an upgrade 
option for SPL. This is partly due to bad design of the socfpga_gen5 
platform. But also I have read multiple times on this list that you 
should use SPL from the same version as U-Boot as they might work 
combined and U-Boot might depend on SPL to do things that might change 
over time. So is it really a good idea to upgrade U-Boot without 
upgrading SPL at the same time? It seems to me this would require 
thorough testing of different version mixes...

So given that SPL must be upgradable, how is it more complex to detect 
U-Boot failure from SPL than from U-Boot itself?

Regards,
Simon