[Mesa-dev] radeon/r200 clear() inconsistency

[Roland Scheidegger]

Brian,

I think you're right, the test in r200_ioctl.c looks bogus
(the idea is fastz clear can only be used if both depth and stencil are
cleared, though the test isn't quite right as it certainly would be
possible to use fastz clear if there's no stencil buffer at all).
However, all code related to hyperz is unfortunately dead anyway, that
got lost with the dri2 transition. The flags computed in those functions
aren't actually used.
I am wondering though how this used to work with that bogus test, I
doubt anyone actually touched that piece since it got useless...

If it ever gets revived it would need to look like hyperz handling in
r300 I think. hyperz in radeon/r200 was always a hack anyway, since it
can only work with one depth buffer, if you switch buffers it will still
use the same on-chip depth buffer tags and the code didn't care about
that, which is the reason why it was never enabled by default - well
that and the fact you couldn't read back compressed (or fastz-cleared)
buffers. r300 solves this (the former problem, not sure about the
latter) by allowing only one app to use a compressed depth buffer IIRC.

Roland


Am 09.03.2012 15:33, schrieb Brian Paul:
> 
> I happened to be looking at radeonClear() and r200Clear() in the legacy
> DRI drivers.  I think there's a bug in one function or the other in the
> hyperz/fastclear test:
> 
> From radeon_ioctl.c:
> 
>    if (rmesa->using_hyperz) {
>       flags |= RADEON_USE_COMP_ZBUF;
> /*      if (rmesa->radeon.radeonScreen->chipset & RADEON_CHIPSET_TCL)
>          flags |= RADEON_USE_HIERZ; */
>       if (((flags & RADEON_DEPTH) && (flags & RADEON_STENCIL) &&
>         ((rmesa->radeon.state.stencil.clear & RADEON_STENCIL_WRITE_MASK)
> == RADEON_STENCIL_WRITE_MASK))) {
>       flags |= RADEON_CLEAR_FASTZ;
>       }
>    }
> 
> From r200_ioctl.c:
> 
>    if (rmesa->using_hyperz) {
>       flags |= RADEON_USE_COMP_ZBUF;
> /*      if (rmesa->radeon.radeonScreen->chip_family == CHIP_FAMILY_R200)
>      flags |= RADEON_USE_HIERZ; */
>       if (!((flags & RADEON_DEPTH) && (flags & RADEON_STENCIL) &&
>         ((rmesa->radeon.state.stencil.clear & R200_STENCIL_WRITE_MASK)
> == R200_STENCIL_WRITE_MASK))) {
>       flags |= RADEON_CLEAR_FASTZ;
>       }
>    }
> 
> 
> Note that the later version has a '!' operator in the second
> if-statement that's not present in the former.  I suspect the ! should
> be removed.
> 
> Can someone familiar with this code take a look?
> 
> -Brian
> 
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