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

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

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;

> @@ -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

-- 
Ville Syrjälä
Intel