[Intel-gfx] [PATCH i-g-t] tests/kms_busy: Only test agains one engine

[Chris Wilson]

Quoting Daniel Vetter (2017-08-03 16:17:57)
> On Thu, Aug 3, 2017 at 2:34 PM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > Quoting Daniel Vetter (2017-08-03 13:05:29)
> >> Back when we used cs flips it made sense to go through different
> >> engines, since a buffer busy on an engine that we couldnt' use for
> >> cs flipping ended up in different paths.
> >>
> >> But with atomic we use a worker for all flips, and going through the
> >> combinatorial growth of engines just wastes precious machine time.
> >> More so the more modern the platform is.
> >
> > Then test against all engines simultaneously.
> 
> What's the benefit of that? Just making sure that we handle multiple
> dma_fence on the same obj/fb? Afaics the current test doesn't do that
> either.

We increase the potential source for errors, keep the cursory check that
any engine can generate content for a flip, and all without adding any
significant time (a couple of extra microseconds to submit, 10us to handle
the extra interrupts).

> >> Of course gem tests should still do some diagonal testing across all
> >> engines, but the kms side can afford to be a bit cheaper.
> >
> > kms has a separate waiting interface, it would be prudent to not assume
> > that coverage elsewhere gives coverage of kms. Note also that kms has a
> > number of special paths for domain handling which require care and
> > attention.
> 
> Again, sounds like a neat extension of test coverage, but I'm just
> aiming to make the current coverage more efficient in terms of machine
> time used.

Indeed, so use all engines instead of an arbitrary choice.
-Chris