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

[Nautiyal, Ankit K]

Thanks Jani for the corrections and suggestions.

I agree to them and will fix them in next version.

Now that I see the commit subject line also should have been "Assume 8 
bpc support when DSC is supported", will change that too.

Regards,

Ankit

On 8/24/2023 3:15 PM, Jani Nikula wrote:
> On Thu, 24 Aug 2023, Ankit Nautiyal <ankit.k.nautiyal at 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 at 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;
>>   }