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

[Dave Airlie]

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.

Dave.