[Mesa-dev] [PATCH 1/3] i965: Don't forget the cube map padding on gen5+.

[Eric Anholt]

Kenneth Graunke <kenneth at whitecape.org> writes:

> On 10/08/2013 10:36 AM, Eric Anholt wrote:
>> We had a fixup for gen4's 3d-layout cubemaps (which, iirc, we'd
>> experimentally found to be necessary!), but while the spec still requires
>> it on gen5, we'd been missing it in the array-layout cubemaps.
>
> Ah, I see it now:
>
> From the Sandybridge PRM, Volume 1, Part 1, Section 7.19...OR...the
> Ivybridge PRM, Volume 1, Part 1, Section 6.19 (Surface Padding
> Requirements):
>
> "For cube surfaces, an additional two rows of padding are required at
> the bottom of the surface.  This must be ensured regardless of whether
> the surface is stored tiled or linear.  This is due to the potential
> rotation of cache line orientation from memory to cache."
>
> So it sounds like this is indeed necessary on all platforms.  Unless
> they just forgot to remove this text from the docs.  Have you observed
> it to fix anything?

No, but it's hard to trigger -- you need your cube map to be large,
unaligned in the y direction, and to land at the very end of the address
space.
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