[PATCH] drm/rockchip: Require the YTR modifier for AFBC

[Brian Starkey]

Hi,

On Tue, Feb 23, 2021 at 02:27:11PM +0000, Daniel Stone wrote:
> Mark, or others from Rockchip, can you please:
> - explain if there is a way to enable/disable the YTR transform in the
> VOP's AFBC decoder, similar to the split-block control bit?
> - ack this patch which correctly declares that the YTR transform is in
> use in order to make Panfrost work, so it can be merged through
> drm-misc, or provide another solution which fixes this API mistake?
> - if VOP does have a hidden YTR-disable bit, add support to disable
> YTR so rockchip-drm can continue advertising the non-YTR modifier, and
> Cc this patch for backporting to every kernel tree which declares AFBC
> modifier support?
> 

Drive-by $0.02:

As described in https://www.kernel.org/doc/Documentation/gpu/afbc.rst,
YTR is only valid for "BGR" component order, so this shouldn't be set
or used for "RGB" order (or YUV) formats. For BGR-order formats, it's
best to always enable YTR to get the best compression ratio.

In an ideal world, there wouldn't be hardware/drivers which
support/allow non-standard encodings, but we don't live in that world
:-(

-Brian

> Thanks in advance.
> 
> Cheers,
> Daniel
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