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

[Wolfgang Denk]

Dear Tom,

In message <20190312140417.GJ4690 at bill-the-cat> you wrote:
> 
> To answer that, no, I don't suppose there's a problem with auditing the
> code to make sure that we can pass in gd, rather than U-Boot proper
> assuming it's the first thing to touch gd, if configured.

> But that to
> me is a different ball of wax.  On this SoC, if you're at the point
> where you're trampling over the defined scratch space that is used for
> other things that need scratch space, you may have other problems too.

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
sets up his stack.  This is what Heiko meant when he wrote: "On
am437x the bootmode info get overwritten from SPL stack." But at
that time the SPL has already loaded this information and maintains
it elsewhere.

I am not aware of any other problems.  Of course one has to re-think
where to place the GD - but this is the same problem as when using
the bloblist and spl_handoff data.

I just feel it makes a lot of sense to use an existing mechanism
across all the boot stages SPL -> ( TPL -> ) U-Boot before
relocation -> U-Boot after relocation, instead of implementing
several different hooks for the same purpose.

[And yes, it might be also time to clean up GD from a lot of mess
that has accumulated there over the last decade.  I doubt many of
these data are really needed there.  But that's another topic, IMO.]

Best regards,

Wolfgang Denk

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