[Mesa-dev] [PATCH 14/30] intel/isl: Add an enum for describing auxiliary compression state

[Jason Ekstrand]

On Tue, Jun 6, 2017 at 6:00 PM, Chad Versace <chad at kiwitree.net> wrote:

> On Tue 06 Jun 2017, Jason Ekstrand wrote:
> > On Tue, Jun 6, 2017 at 1:32 PM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> >
> > > On Tue, Jun 6, 2017 at 1:22 PM, Chad Versace <chadversary at chromium.org
> >
> > > wrote:
> > >
> > >> On Fri 26 May 2017, Jason Ekstrand wrote:
>
> > > How about a section after the auxiliary compression ops section which
> goes
> > > into detail on each of the compression types and discusses which
> states are
> > > valid etc.
> > >
> >
> > How does this look:
> >
> > https://cgit.freedesktop.org/~jekstrand/mesa/commit/?h=wip/
> i965-resolve-rework-v3&id=8478b102c99e3ec43ec687b3f4e52acb9acbd5ba
> >
> > I'll squash it in if you like it.
>
> Please squash that in, with fixes :)
>
> I don't believe the pass-through state is impossible with MCS, because
> there is no single surface for write to "pass through" to. The aux
> surface can never be ignored with MCS. Another bit of evidence for this
> is that there exists no MCS ambiguate op, and therefore no arrow can
> exist in the diagram that carries the "resolved" box to the
> pass-through" box.
>

Too many negatives going on...  I think you meant "I belive the
pass-through state is impossible" :-)

I do not agree.  While no resolve has been written, one could easily do
so.  It would be implemented most likely as a blit from the surface to
itself with MCS enabled on the source and disabled for the destination
followed by blasting the appropriate value into the MCS.  Modulo issues
with the order in which pixels are dispatched (which I don't think is an
actual issue so long as SIMD > num_samples), the result should be a surface
in the pass-through state which can safely be rendered to with MCS
disabled.  Now, why anyone would ever want to do that is beyond me.  The
state which doesn't exist is the regular resolved state because, as with
CCS and MCS, the aux surface stores so little data, that there isn't really
any room for compression when the main surface contains valid data.

--Jason
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