Re: [Intel-gfx] [PATCH 1/2] drm/display/dp: Default 8 bpc support when DSC is supported

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 24 Aug 2023, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
> As per DP v1.4, a DP DSC Sink device shall support 8bpc in DPCD 6Ah.
> Apparently some panels that do support DSC, are not setting the bit for
> 8bpc.
>
> So always assume 8bpc support by DSC decoder, when DSC is claimed to be
> supported.
>
> v2: Use helper to check dsc support. (Ankit)
>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index e6a78fd32380..309fc10cde78 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -2447,14 +2447,19 @@ int drm_dp_dsc_sink_supported_input_bpcs(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_S
>  					 u8 dsc_bpc[3])
>  {
>  	int num_bpc = 0;
> +
> +     if(!drm_dp_sink_supports_dsc(dsc_dpcd))
          ^

Missing space.

> +		return 0;
> +
>  	u8 color_depth = dsc_dpcd[DP_DSC_DEC_COLOR_DEPTH_CAP - DP_DSC_SUPPORT];

All declarations should be before code.

>  
>  	if (color_depth & DP_DSC_12_BPC)
>  		dsc_bpc[num_bpc++] = 12;
>  	if (color_depth & DP_DSC_10_BPC)
>  		dsc_bpc[num_bpc++] = 10;
> -	if (color_depth & DP_DSC_8_BPC)
> -		dsc_bpc[num_bpc++] = 8;
> +
> +	/* A DP DSC Sink devices shall support 8 bpc. */

Mixed singular and plural, a ... devices.

> +	dsc_bpc[num_bpc++] = 8;
>  
>  	return num_bpc;
>  }

-- 
Jani Nikula, Intel Open Source Graphics Center