[Intel-gfx] [PATCH 4/4] drm/i915/dp: Limit max_requested_bpc based on src DSC bpc limits

[Nautiyal, Ankit K]

On 10/25/2023 6:20 PM, Ville Syrjälä wrote:
> On Wed, Oct 25, 2023 at 05:43:18PM +0530, Ankit Nautiyal wrote:
>> At the moment the max requested bpc is limited to 6 to 10/12.
>> For platforms that support DSC, min and max src bpc with DSC are
>> different.
>>
>> Account for DSC bpc limitations, when setting min and max value for
>> max_requested_bpc property.
> NAK. DSC capabiliies change dynamically, the property does not.

Hmm, perhaps I should remove the check for sink DSC support and have 
only Platform check HAS_DSC.

The problem I am trying to fix is that our HW does not support DSC with 
6bpc, but we are allowing the max_requested_bpc to be 6 bpc.

This can be a problem with some eDP panels that support modes like 
4k at 120 which will always need DSC and when max requested bpc property is 
set to 6.

I am wondering how to avoid this. Does it make sense to have the min 
value for the max_requested_bpc to be 8, for platforms that support DSC?

Regards,

Ankit

>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_dp.c | 13 +++++++++++--
>>   1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index abc718f1a878..1935b9014b12 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -5907,8 +5907,17 @@ intel_dp_add_properties(struct intel_dp *intel_dp, struct drm_connector *connect
>>   	intel_attach_broadcast_rgb_property(connector);
>>   	if (HAS_GMCH(dev_priv))
>>   		drm_connector_attach_max_bpc_property(connector, 6, 10);
>> -	else if (DISPLAY_VER(dev_priv) >= 5)
>> -		drm_connector_attach_max_bpc_property(connector, 6, 12);
>> +	else if (DISPLAY_VER(dev_priv) >= 5) {
>> +		int min_bpc = 6, max_bpc = 12;
>> +		struct intel_connector *intel_connector = to_intel_connector(connector);
>> +
>> +		if (HAS_DSC(dev_priv) && drm_dp_sink_supports_dsc(intel_connector->dp.dsc_dpcd)) {
>> +			min_bpc = intel_dp_dsc_min_src_input_bpc(dev_priv);
>> +			max_bpc = intel_dp_dsc_max_src_input_bpc(dev_priv);
>> +		}
>> +
>> +		drm_connector_attach_max_bpc_property(connector, min_bpc, max_bpc);
>> +	}
>>   
>>   	/* Register HDMI colorspace for case of lspcon */
>>   	if (intel_bios_encoder_is_lspcon(dp_to_dig_port(intel_dp)->base.devdata)) {
>> -- 
>> 2.40.1