Re: [Intel-gfx] [PATCH v5 3/9] drm/i915/dp: Replace intel_dp.dfp members with the new crtc_state sink_format

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 11/11/2022 2:36 AM, Ville Syrjälä wrote:
> On Fri, Oct 28, 2022 at 03:14:05PM +0530, Ankit Nautiyal wrote:
>> The decision to use DFP output format conversion capabilities should be
>> during compute_config phase.
>>
>> This patch uses the members of intel_dp->dfp to only store the
>> format conversion capabilities of the DP device and uses the crtc_state
>> sink_format member, to program the protocol-converter for
>> colorspace/format conversion.
>>
>> v2: Use sink_format to determine the color conversion config for the
>> pcon (Ville).
>>
>> v3: Fix typo: missing 'break' in switch case (lkp kernel test robot).
>>
>> v4: Add helper to check if DP supports YCBCR420.
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_dp.c | 122 ++++++++++++++++--------
>>   1 file changed, 84 insertions(+), 38 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 0e4f7b467970..95d0c653db7f 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -790,6 +790,7 @@ intel_dp_output_format(struct intel_connector *connector,
>>   		       enum intel_output_format sink_format)
>>   {
>>   	struct intel_dp *intel_dp = intel_attached_dp(connector);
>> +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>>   
>>   	if (!connector->base.ycbcr_420_allowed ||
>>   	    sink_format != INTEL_OUTPUT_FORMAT_YCBCR420)
>> @@ -799,6 +800,10 @@ intel_dp_output_format(struct intel_connector *connector,
>>   	    intel_dp->dfp.ycbcr_444_to_420)
>>   		return INTEL_OUTPUT_FORMAT_RGB;
>>   
>> +	/* Prefer 4:2:0 passthrough over 4:4:4->4:2:0 conversion */
>> +	if (DISPLAY_VER(i915) >= 11 && intel_dp->dfp.ycbcr420_passthrough)
>> +		return INTEL_OUTPUT_FORMAT_YCBCR420;
>> +
>>   	if (intel_dp->dfp.ycbcr_444_to_420)
>>   		return INTEL_OUTPUT_FORMAT_YCBCR444;
>>   	else
> The else branch here is also 420, so the whole logic
> here doesn't seem to flow entirely sensibly.
>
> Thinking a bit more abstractly, could we restate
> this whole problem as something more like this?
>
> if (source_can_output(sink_format))
> 	return sink_format;
>
> if (source_can_output(RGB) &&
>      dfp_can_convert_from_rgb(sink_format))
> 	return RGB;
>
> if (source_can_output(YCBCR444) &&
>      dfp_can_convert_from_ycbcr444(sink_format))
> 	return YCBCR444;

This make sense and will also help to add 422 support easier.

I am only seeing one problem: about how to have DSC considerations 
during source_can_output( ).

Gen 11+ should support YCBCR420. So for any ycbcr420_only mode we should 
have sink_format, and output_format : YCbCr420.

This works well for cases where DSC doesn't get in picture. When higher 
modes like 8k60 ycbcr420_only are involved, we need to use DSC.

Currently, our DSC1.1 does not support YCbCr420. The problem is that we 
go for, dsc_compute_config at a later time.

This issue might have been masked, due to the messy order of checks in  
intel_dp_output_format.

Specifically With HDMI2.1 PCONs supporting color conv, for such a case 
we can have output_format as RGB, and sink_format as YCbCr420.

The DSC compression with RGB and then configure PCON to Decompress, 
conv. to YCbCr420.

So can we put a check in source_can_output for Gen11+ where DSC might be 
required, so that with source_can_output(YCBCR420) returns false in such 
case, where DSC is the only way?


Regards,

Ankit



>
>> @@ -2668,6 +2673,8 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
>>   					   const struct intel_crtc_state *crtc_state)
>>   {
>>   	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>> +	bool ycbcr444_to_420 = false;
>> +	bool rgb_to_ycbcr = false;
>>   	u8 tmp;
>>   
>>   	if (intel_dp->dpcd[DP_DPCD_REV] < 0x13)
>> @@ -2684,8 +2691,35 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
>>   		drm_dbg_kms(&i915->drm, "Failed to %s protocol converter HDMI mode\n",
>>   			    str_enable_disable(intel_dp->has_hdmi_sink));
>>   
>> -	tmp = crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444 &&
>> -		intel_dp->dfp.ycbcr_444_to_420 ? DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
>> +	if (crtc_state->sink_format == INTEL_OUTPUT_FORMAT_YCBCR420) {
>> +		switch (crtc_state->output_format) {
>> +		case INTEL_OUTPUT_FORMAT_YCBCR420:
>> +			/*
>> +			 * sink_format is YCBCR420, output_format is also YCBCR420:
>> +			 * Passthrough.
>> +			 */
>> +			break;
>> +		case INTEL_OUTPUT_FORMAT_YCBCR444:
>> +			/*
>> +			 * sink_format is YCBCR420, output_format is YCBCR444:
>> +			 * Downsample.
>> +			 */
>> +			ycbcr444_to_420 = true;
>> +			break;
>> +		case INTEL_OUTPUT_FORMAT_RGB:
>> +			/*
>> +			 * sink_format is YCBCR420, output_format is RGB:
>> +			 * Convert to YCBCR444 and Downsample.
>> +			 */
>> +			rgb_to_ycbcr = true;
>> +			ycbcr444_to_420 = true;
>> +			break;
>> +		default:
>> +			break;
>> +		}
>> +	}
>> +
>> +	tmp = ycbcr444_to_420 ? DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
>>   
>>   	if (drm_dp_dpcd_writeb(&intel_dp->aux,
>>   			       DP_PROTOCOL_CONVERTER_CONTROL_1, tmp) != 1)
>> @@ -2693,13 +2727,12 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
>>   			    "Failed to %s protocol converter YCbCr 4:2:0 conversion mode\n",
>>   			    str_enable_disable(intel_dp->dfp.ycbcr_444_to_420));
>>   
>> -	tmp = intel_dp->dfp.rgb_to_ycbcr ?
>> -		DP_CONVERSION_BT709_RGB_YCBCR_ENABLE : 0;
>> +	tmp = rgb_to_ycbcr ? DP_CONVERSION_BT709_RGB_YCBCR_ENABLE : 0;
>>   
>>   	if (drm_dp_pcon_convert_rgb_to_ycbcr(&intel_dp->aux, tmp) < 0)
>>   		drm_dbg_kms(&i915->drm,
>> -			   "Failed to %s protocol converter RGB->YCbCr conversion mode\n",
>> -			   str_enable_disable(tmp));
>> +			    "Failed to %s protocol converter RGB->YCbCr conversion mode\n",
>> +			    str_enable_disable(tmp));
>>   }
>>   
>>   bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp)
>> @@ -4544,57 +4577,70 @@ intel_dp_update_dfp(struct intel_dp *intel_dp,
>>   	intel_dp_get_pcon_dsc_cap(intel_dp);
>>   }
>>   
>> -static void
>> -intel_dp_update_420(struct intel_dp *intel_dp)
>> +static bool
>> +intel_dp_can_ycbcr420(struct intel_connector *connector)
>>   {
>> +	struct intel_dp *intel_dp = intel_attached_dp(connector);
>>   	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>> -	struct intel_connector *connector = intel_dp->attached_connector;
>> -	bool is_branch, ycbcr_420_passthrough, ycbcr_444_to_420, rgb_to_ycbcr;
>> +	bool is_branch = drm_dp_is_branch(intel_dp->dpcd);
>>   
>>   	/* No YCbCr output support on gmch platforms */
>>   	if (HAS_GMCH(i915))
>> -		return;
>> +		return false;
>>   
>>   	/*
>>   	 * ILK doesn't seem capable of DP YCbCr output. The
>>   	 * displayed image is severly corrupted. SNB+ is fine.
>>   	 */
>>   	if (IS_IRONLAKE(i915))
>> -		return;
>> +		return false;
>> +	/*
>> +	 * For Display < 11, YCBCR420 output possible only
>> +	 * if DFP supports 444->420 conversion.
>> +	 */
>> +	if (DISPLAY_VER(i915) < 11)
>> +		return is_branch && intel_dp->dfp.ycbcr_444_to_420;
>> +
>> +	/*
>> +	 * For Display > 11:
>> +	 * If not a branch device, can support YCBCR420.
>> +	 */
>> +	if (!is_branch)
>> +		return true;
>> +
>> +	/*
>> +	 * If branch device then either:
>> +	 * 1. PCONs should support YCBCR420 Passthrough
>> +	 * i.e.Source uses CSC, scaler to convert RGB->YCBCR420 and
>> +	 * sends YCBCR420 to PCON. PCON 'passrthrough' YCBCR420 to sink.
>> +	 * Or
>> +	 * 2. PCONs should support 444->420
>> +	 * (Source sends YCBCR444 PCON converts YCBCR444->420)
>> +	 * (Source sends RGB4444 PCON converts RGB->YCBCR444 and YCBCR444->YCBCR420)
>> +	 */
>> +	return intel_dp->dfp.ycbcr420_passthrough || intel_dp->dfp.ycbcr_444_to_420;
>> +}
>>   
>> -	is_branch = drm_dp_is_branch(intel_dp->dpcd);
>> -	ycbcr_420_passthrough =
>> +static void
>> +intel_dp_update_420(struct intel_dp *intel_dp)
>> +{
>> +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>> +	struct intel_connector *connector = intel_dp->attached_connector;
>> +
>> +	intel_dp->dfp.ycbcr420_passthrough =
>>   		drm_dp_downstream_420_passthrough(intel_dp->dpcd,
>>   						  intel_dp->downstream_ports);
>>   	/* on-board LSPCON always assumed to support 4:4:4->4:2:0 conversion */
>> -	ycbcr_444_to_420 =
>> +	intel_dp->dfp.ycbcr_444_to_420 =
>>   		dp_to_dig_port(intel_dp)->lspcon.active ||
>>   		drm_dp_downstream_444_to_420_conversion(intel_dp->dpcd,
>>   							intel_dp->downstream_ports);
>> -	rgb_to_ycbcr = drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
>> -								 intel_dp->downstream_ports,
>> -								 DP_DS_HDMI_BT709_RGB_YCBCR_CONV);
>> -
>> -	if (DISPLAY_VER(i915) >= 11) {
>> -		/* Let PCON convert from RGB->YCbCr if possible */
>> -		if (is_branch && rgb_to_ycbcr && ycbcr_444_to_420) {
>> -			intel_dp->dfp.rgb_to_ycbcr = true;
>> -			intel_dp->dfp.ycbcr_444_to_420 = true;
>> -			connector->base.ycbcr_420_allowed = true;
>> -		} else {
>> -		/* Prefer 4:2:0 passthrough over 4:4:4->4:2:0 conversion */
>> -			intel_dp->dfp.ycbcr_444_to_420 =
>> -				ycbcr_444_to_420 && !ycbcr_420_passthrough;
>> +	intel_dp->dfp.rgb_to_ycbcr =
>> +		drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
>> +							  intel_dp->downstream_ports,
>> +							  DP_DS_HDMI_BT709_RGB_YCBCR_CONV);
>>   
>> -			connector->base.ycbcr_420_allowed =
>> -				!is_branch || ycbcr_444_to_420 || ycbcr_420_passthrough;
>> -		}
>> -	} else {
>> -		/* 4:4:4->4:2:0 conversion is the only way */
>> -		intel_dp->dfp.ycbcr_444_to_420 = ycbcr_444_to_420;
>> -
>> -		connector->base.ycbcr_420_allowed = ycbcr_444_to_420;
>> -	}
>> +	connector->base.ycbcr_420_allowed = intel_dp_can_ycbcr420(connector);
>>   
>>   	drm_dbg_kms(&i915->drm,
>>   		    "[CONNECTOR:%d:%s] RGB->YcbCr conversion? %s, YCbCr 4:2:0 allowed? %s, YCbCr 4:4:4->4:2:0 conversion? %s\n",
>> -- 
>> 2.25.1