[Lima] [PATCH v3] drm/fourcc: add ARM GPU tile modifier

[Qiang Yu]

Hi Brian,

> Since your first patch set, I did raise this internally. The request
> has been making it's way through:
>
>  - GPU engineering, to determine what exactly this format is, and
>    what other variants there might be which are supported on different
>    GPU generations, so that we can determine a sane naming convention.
>
>  - Our legal team, to determine what detail we are happy to share from
>    an IP perspective. I can't imagine there being an issue here, but
>    process is process, and there's not a lot I can do to move that
>    along.
>
> There was talk on the legal side last week. I will ask for an update.
> I realise this is taking a very long time, and for that I can only
> apologise; I really am trying to get you an answer.

Thanks for the update and your effort to make a generic solution on
the ARM side. It's really some time passed since last time we talked
about this, but I think it's worth to wait for more time to get a reliable
solution with more internal information known by us.

> For other layouts which don't have this kind of combinatorial effect,
> I'd rather have #defines for the specific layouts, all individually
> setting the top bit, without giving that top bit any kind of "name".
> The top bit would effectively mean "not AFBC", rather than meaning
> "AGTB", allowing us to use the lower bits more freely.
>
Seems like another kind of category, but with different meaning.

> If you can hang on a while longer, I hope Arm can push a patch which
> you can just use directly, and then handling the bit assignments will
> be our mess rather than yours :-)
>
That's better, I can wait :-)

Thanks,
Qiang

> > +#define DRM_FORMAT_MOD_ARM_CODE(type, val) \
> > +     fourcc_mod_code(ARM, ((__u64)type << 48) | ((val) & 0x0000ffffffffffffULL))
> > +
> >  /*
> >   * Arm Framebuffer Compression (AFBC) modifiers
> >   *
> > @@ -615,7 +628,8 @@ extern "C" {
> >   * Further information on the use of AFBC modifiers can be found in
> >   * Documentation/gpu/afbc.rst
> >   */
> > -#define DRM_FORMAT_MOD_ARM_AFBC(__afbc_mode) fourcc_mod_code(ARM, __afbc_mode)
> > +#define DRM_FORMAT_MOD_ARM_AFBC(__afbc_mode) \
> > +     DRM_FORMAT_MOD_ARM_CODE(DRM_FORMAT_MOD_ARM_TYPE_AFBC, __afbc_mode)
> >
> >  /*
> >   * AFBC superblock size
> > @@ -709,6 +723,21 @@ extern "C" {
> >   */
> >  #define AFBC_FORMAT_MOD_BCH     (1ULL << 11)
> >
> > +/*
> > + * Arm Graphics Tiled Buffer (AGTB) modifiers
> > + */
> > +#define DRM_FORMAT_MOD_ARM_AGTB(mode) \
> > +     DRM_FORMAT_MOD_ARM_CODE(DRM_FORMAT_MOD_ARM_TYPE_AGTB, mode)
> > +
> > +/*
> > + * AGTB mode 0 modifier
> > + *
> > + * This is used by ARM Mali Utgard/Midgard GPU. It divides buffer into
> > + * 16x16 pixel blocks. Blocks are stored linearly in order, but pixels
> > + * in the block are reordered.
> > + */
> > +#define DRM_FORMAT_MOD_ARM_AGTB_MODE0 DRM_FORMAT_MOD_ARM_AGTB(1)
> > +
> >  /*
> >   * Allwinner tiled modifier
> >   *
> > --
> > 2.17.1
> >