[coreboot] Add coreboot storage driver

[Timothy Pearson]

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On 02/13/2017 01:19 AM, Andrey Petrov wrote:
<snip>
> For [2] we have been working on prototype for Apollolake that does
> pre-memory MPinit. We've got to a stage where we can run C code on
> another core before DRAM is up (please do not try that at home, because
> you'd need custom experimental ucode).

In addition to the very valid points raised by others on this list, this
note in particular is concerning.  Whenever we start talking about
microcode, we're talking about yet another magic black box that coreboot
has no control over and cannot maintain.  Adding global functionality
that is so system specific in practice as to rely on microcode feature
support is not something I ever want to see, unless perhaps the relevant
portions of the microcode are open and maintainable by the coreboot project.

In a nutshell, this proposal would make it even harder for any low-level
coreboot development on these systems to take place outside of Intel,
and as one of the main coreboot contractors this "soft lockdown" is
something we are strongly opposed to.  Furthermore, I suggest looking at
the AMD K8 memory init code -- some basic parallelism was introduced for
memory clear, but in the end the improved boot speed was not a "killer
feature" and had the side effect of making the code difficult to
maintain, leaving the K8 support permanently broken as of this writing.

- -- 
Timothy Pearson
Raptor Engineering
+1 (415) 727-8645 (direct line)
+1 (512) 690-0200 (switchboard)
https://www.raptorengineering.com
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