[igt-dev] [PATCH i-g-t] tests/gem_render_copy: Add software tiling / detiling support

[Zbigniew Kempczyński]

On Fri, Nov 29, 2019 at 10:13:48AM +0000, Chris Wilson wrote:
> Quoting Zbigniew Kempczyński (2019-11-29 09:36:53)
> > Older GENs have mmapable GGTT which does buffer tiling / detaling
> > automatically. Newer GENs have looses this possibility so software
> > tiling / detiling is required.
> 
> A bunch of trivial checks to ensure idempotence (i.e linear -> X ->
> linear) with 4K and 2M and a bunch of tiling strides would be useful.
> 
> Note that these functions only correspond to HW detiling when swizzling
> is off -- you can ask the kernel via GET_TILING_IOCTL.
> -Chris

I thought about above check. But this would tie my hands if I would like
to use mix software tiling / hw detiling. Thus I decided to set function
pointers manually according to generation. 

If I good understand you:
You suggest to create single structure (instead of arrays), detect hw
tiling/detiling capabilities for each supported tile (X / Y)
and fill appropriate functions?

But I still need some table containing information about all tile formats
HW supports (for example Yf on Gen9+ even if we can't put it via 
gtt, because it won't tile it in the fly). In this situation I don't 
know is it possible to ask the HW about is it supports Yf format).

Zbigniew