[Freedreno] [PATCH v10 4/8] drm/msm: Add MSM-specific DSC helper methods

[Marijn Suijten]

On 2023-05-16 01:07:05, Dmitry Baryshkov wrote:
> 
> On 16/05/2023 01:01, Marijn Suijten wrote:
> > On 2023-05-15 13:29:21, Jessica Zhang wrote:
> > <snip>
> >>> Const, as requested elsewhere.  But this function is not used anywhere
> >>> in any of the series (because we replaced the usages with more sensible
> >>> member accesses like slice_chunk_size).
> >>
> >> Acked.
> >>
> >> I would prefer to keep this helper so that we have a way to easily get
> >> BPP information from the DRM DSC config in the future, but if you'd
> >> prefer we add this helper then, I'm also ok with that.
> > 
> > The inverse helper is available ad DSC_BPP in drm_dsc_helper.c.  Perhaps
> > we can move the two variants to the header and define them uniformly?
> > This isn't MSM-specific it seems (i.e. the format supports fractional
> > bpp but no RC parameters appear to be defined for such a format yet).
> 
> I think DSC_BPP was removed (around v2 or v3 if I read changelog correctly).

Seems like it was removed at some point indeed, and now the helper file
picked up an identically named DSC_BPP macro but with the inverse
implementation :) - at least it's a *.c file.

Perhaps we can make it more consistent by defining both ways with
concise macros in a header.

> As for the fraction-point BPP, I think AMD supports .5 bpp granularity, 
> see drivers/gpu/drm/amd/display/dc/dml/dsc/qp_tables.h

That won't use the helper then.

> With best wishes
> Dmitry

- Marijn