[Intel-gfx] [PATCH 0/8] [RFC] Link training test

[Ander Conselvan de Oliveira]

Hi,

There's been some discussion on improving our link training code, with
one of the ideas being a complete rewrite of the state machine. However,
a concern was raised over the risk of regressions. The code we have has
seen a lot of real world testing, and it would take a long time for any
new code to get that same exposure. On top of that, there is no explicit
igt coverage for link training since it is very dependent on the hw
setup.

Since gathering an extensive set of hardware combinations for getting the
appropriate test coverage is really difficult, I believe that we should
aim at testing the link training code in isolation. That's what this RFC
is about.

Most of the kernel patches in this series are small changes to the hw
independent part of the link training code that make it possible to move
it to a separate file.  Then, in the igt patch, a test is created the
wraps a fake DP sink device around the link training code. The behavior
of that sink device is pretty simple for now, it just tries to get the
maximum voltage swing and pre-emphasis level supported. We could do some
git archeology of the link training code to try to find some more tests
that would make sense.

I had to make a lot of hacks to get that thing to compile, so that's
one of the things I'd like to hear comments on. And also on the general
approach.

Thanks,
Ander

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2.4.3