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

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

On Wed, 30 Aug 2023, "Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com> wrote:
> 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@intel.com>
>
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

Pushed both to drm-intel-next, with Maxime's ack, thanks for the patches
and review.

BR,
Jani.

>
>> ---
>>  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;
>>  }

-- 
Jani Nikula, Intel Open Source Graphics Center