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

[Jessica Zhang]

On 5/15/2023 3:07 PM, 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).

Hi Dmitry,

That's correct, we did have a DSC_BPP macro with the same functionality 
as msm_dsc_get_bpp_int, but it was renamed in v2 to msm_dsc_get_bpp_int 
(there's a typo in the changelog... I will correct that in the next 
revision).

However, I do see a DSC_BPP macro in drm_dsc_helper.c that has a 
different functionality.

Thanks,

Jessica Zhang

> 
> 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
> 
> -- 
> With best wishes
> Dmitry
>