[U-Boot] passing info from SPL to U-Boot

[Wolfgang Denk]

Dear Tom,

In message <20190312173125.GP4690 at bill-the-cat> you wrote:
> 
> > I think you were misled by Heiko's description.  What he really ment
> > was just that the addresses where the boot ROM stored the
> > information about the boot device etc. gets overwriteen when the SPL
>
> For clarity, that's not _quite_ it.  The ROM passes the value in a
> register and we move that to scratch space, see
> arch/arm/mach-omap2/lowlevel_init.S and save_boot_params.  This is done
> on every 32bit Cortex-A TI platform.
...
> OK, but here's the problem.  We define off, iirc, 1KiB of that SRAM
> space as not-stack but scratch space to store stuff in.  The first
> problem you will hit, if something else touches that scratch space is
> what Heiko found, the boot value got blown away.

I see.  Well, I think it's best if Heiko explains in detail; what he
has observed, and what when which part of the information got lost.
I was just interpreting his mail, so I may easily have misunderstood
this.

@ Heiko:  Can you please elucidate?


> I agree here.  Fixing things up such that we can pass things we know
> =66rom one stage to another in a defined manner, rather than ad-hoc
> manner, is good.  We could even, probably, re-work most of that use of
> scratch space to be done in another way, or make it safe to re-use
> later.

Thanks a lot!  Let's go for it.

Best regards,

Wolfgang Denk

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