[RFC/WIP] drm/rockchip: Support CRTC gamma LUT

[Ilia Mirkin]

On Tue, Jun 18, 2019 at 9:36 AM Ezequiel Garcia <ezequiel at collabora.com> wrote:
>
> On Thu, 2019-06-13 at 15:36 -0400, Ilia Mirkin wrote:
> > Note that userspace may provide any size of gamma lut. Have a look at
> > i915/intel_color.c:intel_color_check which filters out only the
> > allowed sizes. Consider having a special allowance for 256-sized LUTs
> > since that's what most legacy userspace will set, and it seems like a
> > waste to create a 10-bit LUT for RGBA8 color.
> >
>
> Right. I will add a check for the gamma lut size.
>
> Unfortunately, this hardware seems to only support 10-bit, 1024-sized LUTs.
>
> The spec does mention a support 8-bit, 256-entries, but it's not at all
> clear how configure that.

It's up to you, and the more experienced drm reviewers, but even if
you can't figure out how to bend the hardware to your will (which is
worth a bit of exploration), you can still emulate it by just
repeating all the values 4x. IMHO 256-sized LUTs are worth supporting
when possible.

Cheers,

  -ilia