[igt-dev] [PATCH] drm/doc: Make igts for cross-driver stuff mandatory

[Daniel Vetter]

On Tue, Jan 22, 2019 at 8:00 PM Wentland, Harry <Harry.Wentland at amd.com> wrote:
> On 2019-01-16 11:39 a.m., Daniel Vetter wrote:
> > Compared to the RFC[1] no changes to the patch itself, but igt moved
> > forward a lot:
> >
> > - gitlab CI builds with: reduced configs/libraries, arm cross build
> >   and a sysroot build (should address all the build/cross platform
> >   concerns raised in the RFC discussions).
> >
> > - tests reorganized into subdirectories so that the i915-gem tests
> >   don't clog the main/shared tests directory anymore
> >
> > - quite a few more non-intel people contributing/reviewing/committing
> >   igt tests patches.
> >
> > I think this addresses all the concerns raised in the RFC discussions,
> > and assuming there's enough Acks and no new issues that pop up, we can
> > go ahead with this.
> >
> > 1: https://patchwork.kernel.org/patch/10648851/
> > Cc: Petri Latvala <petri.latvala at intel.com>
> > Cc: Arkadiusz Hiler <arkadiusz.hiler at intel.com>
> > Cc: Liviu Dudau <liviu.dudau at arm.com>
> > Cc: Sean Paul <sean at poorly.run>
> > Cc: Eric Anholt <eric at anholt.net>
> > Cc: Alex Deucher <alexander.deucher at amd.com>
> > Cc: Dave Airlie <airlied at redhat.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>
> I'm all for anything resembling TDD and standardizing on one test framework. IGT works quite well for us for testing display stuff. We still have a way to go but have been trying to adopt this requirement lately anyways for the DC driver. Can't really comment on anything beyond display, though, for AMD.
>
> No matter how much I want this to be mandatory, seeing the discussions with ARM and the comment about lack of CRC on Nouveau makes me think that we might not be quite ready to go there. Implementing DWB is non-trivial. VKMS knows how to compute a CRC from a framebuffer, but that's the trivial part. Setting up the HW and SW to do DWB is the hard part.

We also discussed a bit writeback implementations on irc, and it looks
like you can't really use writeback to accurately test that your
compositing engine is programmed correctly, since on at least vc4,
malidp and msm (not yet merged upstream) the writeback engine can't be
shared with any other outputs, often it even needs a
dedicated/special-purpose CRTC (at least vc4 from what I can tell).
That means if you botch your programming and e.g. cause an underrun
scanning out continous-update outputs, then the writeback won't show
that to you, since it's composited separately. I guess we could teach
igt to run these tests on the special crtc->writeback pipeline only,
but essentially that's a new testcase, and not really testing the
actual display: It tests writeback, not hdmi/dp/panels/whatever real
outputs you have.

I'd say we'll shrug these cases off as "can't be reasonable tested,
won't have an igt". First driver team with hw that can be validated
gets to fill the gaps :-) In practice still going to be a lot better
than no tests at all, just exercising the feature will be useful, and
will make it a lot easier for the next team to add the crc based tests
on top.

-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch