[Mesa-dev] [PATCH] radeon: fix r600/7 fmask pitch

[Alex Deucher]

On Wed, Jan 7, 2015 at 8:19 PM, Dave Airlie <airlied at gmail.com> wrote:
> Okay I've been doing some further FMASK studies empirically, dumping
> the fmask after rendering to an MSAA surface,
>
> it appears on r600 at 8xMSAA, every 8x8 tile requires 128 bytes of
> storage, that is used depending on the value in the CMASK.
>
> So it appears at 8xMSAA for every 4-bit entry in the CMASK we need to
> allocate 128-bytes in the FMASK, now the FMASK appears to tile the
> CMASK entries as well inside a macrotile layout.
>
> At this point I think the tiling docs I have are just wrong for r600,
> as they state at 8xMSAA with 8x8 tile, it should be w*h*(samples / 8)
> *log2(samples) which for me is 8x8x1x3, which is 196 bytes, which
> clearly the hw isn't doing.
>
> Anyone from AMD have more accurate info or should I just hack this, I
> get the feeling overallocating the FMASK is better than what we do now
> anyways.

I can dig around a bit, but most of the r600 stuff is not really fresh
in anyone's mind.  I'm fine with just overallocating it at this point.

Alex