[coreboot] Add coreboot storage driver

[Nico Huber]

On 14.02.2017 18:56, ron minnich wrote:
> At what point is ramstage a kernel? I think at the point we add file
> systems or preemptive scheduling. We're getting dangerously close. If we
> really start to cross that boundary, it's time to rethink the ramstage in
> my view. It's not a good foundation for a kernel.

Agreed. I wouldn't call it a kernel, but it really seems to grow very
ugly. Every time I think about this, I scarcely find anything that needs
to be done in ramstage. I believe even most payloads could live without
it with some more initialization done in romstage.

Some things that I recall, what ramstage does:

  o MP init => maybe can be done earlier, does it need RAM generally???

  o PCI resource allocation => can be done offline
    Just add the resources to the devicetree. If you want to boot
    from a plugged card, that isn't in the devicetree, the payload
    would have to handle it though.

  o Those small PCI device "drivers" => I doubt they need RAM

  o Table generation => Not that dynamic after all
    I suppose much is done with static (compile time) information.

  o Sometimes gfx modesetting => do it in the payload

Nico