[1/2] drm/display/dp: Assume 8 bpc support when DSC is supported

[Lisovskiy, Stanislav]

On Thu, Aug 24, 2023 at 06:21:20PM +0530, Ankit Nautiyal 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 get check dsc support. (Ankit)
> v3: Fix styling and other typos. (Jani)
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>

> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 8 ++++++--
>  1 file changed, 6 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..8a1b64c57dfd 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -2449,12 +2449,16 @@ int drm_dp_dsc_sink_supported_input_bpcs(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_S
>  	int num_bpc = 0;
>  	u8 color_depth = dsc_dpcd[DP_DSC_DEC_COLOR_DEPTH_CAP - DP_DSC_SUPPORT];
>  
> +	if (!drm_dp_sink_supports_dsc(dsc_dpcd))
> +		return 0;
> +
>  	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 device shall support 8 bpc. */
> +	dsc_bpc[num_bpc++] = 8;
>  
>  	return num_bpc;
>  }