[PATCH 4/7] drm/meson: plane: add support for AFBC mode for OSD1 plane

[Brian Starkey]

On Fri, Oct 11, 2019 at 07:25:02PM +0200, Daniel Vetter wrote:
> On Fri, Oct 11, 2019 at 12:56 PM Brian Starkey <Brian.Starkey at arm.com> wrote:
> >
> > Hi,
> >
> > On Fri, Oct 11, 2019 at 11:14:43AM +0200, Neil Armstrong wrote:
> > > Hi Brian,
> > >
> > > On 11/10/2019 10:41, Brian Starkey wrote:
> 
> > > > Are you sure the GPU supports other orders? I think any Arm driver
> > > > will only be producing DRM_FORMATs with "BGR" order e.g. ABGR888>
> > > > I'm not convinced the GPU HW actually supports any other order, but
> > > > it's all rather confusing with texture swizzling. What I can tell you
> > > > for sure is that it _does_ support BGR order (in DRM naming
> > > > convention).
> > >
> > > Well, since the Bifrost Mali blobs are closed-source and delivered
> > > by licensees, it's hard to define what is supported from a closed
> > > GPU HW, closed SW implementation to a closed pixel format implementation.
> > >
> >
> > I hear you. IMO the only way to make any of this clear is to publish
> > reference data and tests which make sure implementations match each
> > other. It's something I'm trying to make happen.
> 
> *cough* igt test with crc/writeback validation *cough*
> 
> And you don't even need anything that actually compresses. All you
> need is the minimal enough AFBC knowledge to set up the metadata that
> everything is uncompressed. We're doing that for our intel compression
> formats already, and it works great in making sure that we have
> end-to-end agreement on all the bits and ordering and everything.

Yeah this was my original thinking too. Sadly, a decent number of the
AFBC parameters can't be tested with uncompressed data, as the codec
kicks into a different mode there.

> Ofc
> it doesn't validate the decoder, but that's not really igts job.
> Should be possible to convince ARM to release that (as open source, in
> igt), since it would be fairly valuable for the entire ecosystem here
> ...

I fully agree about the value proposition.

-Brian

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