Re: [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@xxxxxxxxx>]

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@xxxxxxxxx>
> > ---
> >   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