Re: [igt-dev] [PATCH i-g-t] lib/rendercopy_gen9: Set rw domains to zero for GEN12

Imre Deak
2019-11-28T10:32:14Z

On Thu, Nov 28, 2019 at 09:16:20AM +0000, Chris Wilson wrote:
> Quoting Mika Kahola (2019-11-28 09:12:28)
> > GEN12 doesn't need read and write domains to be set. Let's set
> > these to zero in case of GEN12.
>
> Why gen12? For the entire file the only bit that is significant is
> write_domain != 0

Err, that idea was mine, but then it was wrong. Mika needs to add a
relocation on this surface state to the color key data that's where this
change comes from.

Didn't think about the write domain being significant even on LLC
platforms, so let's just drop my idea for now (was only for clarity when
emitting relocations on GEN12) and use the same read/write domains as on
other platforms.

For reference could you explain how the write domain is signicant on LLC
platforms? (My guess now is that the kernel can wait for writes on the
surface to finnish, but it doesn't need it to flush caches, which is not
necessary on LLC.)

Thanks,
Imre