glxgears on Etnaviv: couldn't get an RGB, Double-buffered visual

[l.stach@pengutronix.de (Lucas Stach)]

Am Freitag, den 24.11.2017, 16:49 +0000 schrieb Alexey Brodkin:
[...]
> > Yes, a "core" in Vivante speak is a GPU with one DMA frontend. A
> > single
> > frontend can feed both 3D and 2D acceleration engines behind it. On
> > i.MX6 the 2D and 3D engine are on separate cores, but Marvell Dove
> > has
> > a combined 2D/3D core.
> 
> Hm, that sounds encouraging. The next question would be if Marvel
> Dove is
> supported in Etnaviv DDX? I guess it's called Armada so the answer if
> yes, right?

Yes, the Dove was the original platform for the Armada X.Org driver.
Combined 2D/3D cores are supported just fine by etnaviv.

> > > If we happen to not have 2D core if that's a no go for us for
> > > anything?
> > 
> > I don't know if the DDX works properly without 2D acceleration.
> > Weston
> > on the other hand only relies on the 3D accel core for doing
> > compositing, so even if you don't have a 2D engine you will be able
> > to
> > launch a modern Linux graphics stack.
> 
> That's really cool! I'm much more interested in Weston ATM, which is
> actually another separate question :)
> I tried to find some details on how to run Weston on Wandboard
> but seems like I was looking at wrong Google again... do you
> know any good manuals for doing that?

There really is no magic to it. Or better there is, but it's all hidden
in the Mesa implementation.

You need at least Mesa 17.2 and Weston 3.0 for etnaviv to work
properly. Other than that just set XDG_RUNTIME_DIR to something
sensible and launch Weston with "weston --tty=63", done.

> > 
> > The etnaviv DDX could also emulate 2D accel over the 3D core by
> > using
> > the X.Org glamor module, but no one has bothered to implement this
> > yet.
> 
> Ok we'll see if above case (combined cores) is applicable to us and
> then
> we'll see what to do.
> 
> > > In the meantime I'll try to figure out if we have 2D core or not.
> > 
> > You can find out what your GPU provides by looking at the feature
> > bits.
> > chipFeatures_PIPE_2D, chipFeatures_PIPE_3D and chipFeatures_PIPE_VG
> > is
> > what you are looking out for.
> 
> Does that info helps to decipher these bits?

Unfortunately we forgot to expose the major feature bits register in
debugfs. It's gpu->identity.features in the kernel driver, the
interesting bits in there are chipFeatures_PIPE_3D and
chipFeatures_PIPE_2D.

Regards,
Lucas