drm/i915/display: Let PCON convert from RGB to YCbCr if it can

If PCON has capability to convert RGB->YCbCr colorspace and also
to 444->420 downsampling then for any YUV420 only mode, we can
let the PCON do all the conversion. If the PCON supports
RGB->YCbCr conversion for all BT2020, BT709, BT601, choose
the one that is selected by userspace via connector colorspace
property, otherwise default to BT601.

v2: As suggested by Uma Shankar, considered case for colorspace
BT709 and BT2020, and default to BT601. Also appended dir
'display' in commit message.

v3: Fixed typo in condition for printing one of the error msg.

v4: As suggested by Uma Shankar:
-Fixed bug in determining the colorspace for RGB->YCbCr conversion.
-Fixed minor formatting issues
Also updated the commit message as per latest changes.
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
[Jani: Fixed checkpatch PARENTHESIS_ALIGNMENT.]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-16-ankit.k.nautiyal@intel.com

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -3643,6 +3643,7 @@ static void tgl_ddi_pre_enable_dp(struct intel_atomic_state *state,
 	if (!is_mst)
 		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
 
+	intel_dp_configure_protocol_converter(intel_dp, crtc_state);
 	intel_dp_sink_set_decompression_state(intel_dp, crtc_state, true);
 	/*
 	 * DDI FEC: "anticipates enabling FEC encoding sets the FEC_READY bit
@@ -3728,7 +3729,7 @@ static void hsw_ddi_pre_enable_dp(struct intel_atomic_state *state,
 	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
 	if (!is_mst)
 		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
-	intel_dp_configure_protocol_converter(intel_dp);
+	intel_dp_configure_protocol_converter(intel_dp, crtc_state);
 	intel_dp_sink_set_decompression_state(intel_dp, crtc_state,
 					      true);
 	intel_dp_sink_set_fec_ready(intel_dp, crtc_state);

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1441,6 +1441,7 @@ struct intel_dp {
 		int pcon_max_frl_bw;
 		u8 max_bpc;
 		bool ycbcr_444_to_420;
+		bool rgb_to_ycbcr;
 	} dfp;
 
 	/* Display stream compression testing */

drivers/gpu/drm/i915/display/intel_dp.c

@@ -651,6 +651,10 @@ intel_dp_output_format(struct drm_connector *connector,
 	    !drm_mode_is_420_only(info, mode))
 		return INTEL_OUTPUT_FORMAT_RGB;
 
+	if (intel_dp->dfp.rgb_to_ycbcr &&
+	    intel_dp->dfp.ycbcr_444_to_420)
+		return INTEL_OUTPUT_FORMAT_RGB;
+
 	if (intel_dp->dfp.ycbcr_444_to_420)
 		return INTEL_OUTPUT_FORMAT_YCBCR444;
 	else
@@ -4305,7 +4309,8 @@ static void intel_dp_enable_port(struct intel_dp *intel_dp,
 	intel_de_posting_read(dev_priv, intel_dp->output_reg);
 }
 
-void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp)
+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);
 	u8 tmp;
@@ -4334,12 +4339,42 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp)
 			    enableddisabled(intel_dp->dfp.ycbcr_444_to_420));
 
 	tmp = 0;
+	if (intel_dp->dfp.rgb_to_ycbcr) {
+		bool bt2020, bt709;
 
-	if (drm_dp_dpcd_writeb(&intel_dp->aux,
-			       DP_PROTOCOL_CONVERTER_CONTROL_2, tmp) <= 0)
+		/*
+		 * FIXME: Currently if userspace selects BT2020 or BT709, but PCON supports only
+		 * RGB->YCbCr for BT601 colorspace, we go ahead with BT601, as default.
+		 *
+		 */
+		tmp = DP_CONVERSION_BT601_RGB_YCBCR_ENABLE;
+
+		bt2020 = drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
+								   intel_dp->downstream_ports,
+								   DP_DS_HDMI_BT2020_RGB_YCBCR_CONV);
+		bt709 = drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
+								  intel_dp->downstream_ports,
+								  DP_DS_HDMI_BT709_RGB_YCBCR_CONV);
+		switch (crtc_state->infoframes.vsc.colorimetry) {
+		case DP_COLORIMETRY_BT2020_RGB:
+		case DP_COLORIMETRY_BT2020_YCC:
+			if (bt2020)
+				tmp = DP_CONVERSION_BT2020_RGB_YCBCR_ENABLE;
+			break;
+		case DP_COLORIMETRY_BT709_YCC:
+		case DP_COLORIMETRY_XVYCC_709:
+			if (bt709)
+				tmp = DP_CONVERSION_BT709_RGB_YCBCR_ENABLE;
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (drm_dp_pcon_convert_rgb_to_ycbcr(&intel_dp->aux, tmp) < 0)
 		drm_dbg_kms(&i915->drm,
-			    "Failed to set protocol converter YCbCr 4:2:2 conversion mode to %s\n",
-			    enableddisabled(false));
+			   "Failed to set protocol converter RGB->YCbCr conversion mode to %s\n",
+			   enableddisabled(tmp ? true : false));
 }
 
 static void intel_enable_dp(struct intel_atomic_state *state,
@@ -4379,7 +4414,7 @@ static void intel_enable_dp(struct intel_atomic_state *state,
 	}
 
 	intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
-	intel_dp_configure_protocol_converter(intel_dp);
+	intel_dp_configure_protocol_converter(intel_dp, pipe_config);
 	intel_dp_check_frl_training(intel_dp);
 	intel_dp_pcon_dsc_configure(intel_dp, pipe_config);
 	intel_dp_start_link_train(intel_dp, pipe_config);
@@ -6847,7 +6882,7 @@ 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;
-	bool is_branch, ycbcr_420_passthrough, ycbcr_444_to_420;
+	bool is_branch, ycbcr_420_passthrough, ycbcr_444_to_420, rgb_to_ycbcr;
 
 	/* No YCbCr output support on gmch platforms */
 	if (HAS_GMCH(i915))
@@ -6869,14 +6904,26 @@ intel_dp_update_420(struct intel_dp *intel_dp)
 		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_BT601_RGB_YCBCR_CONV ||
+								 DP_DS_HDMI_BT709_RGB_YCBCR_CONV ||
+								 DP_DS_HDMI_BT2020_RGB_YCBCR_CONV);
 
 	if (INTEL_GEN(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.ycbcr_444_to_420 =
+				ycbcr_444_to_420 && !ycbcr_420_passthrough;
 
-		connector->base.ycbcr_420_allowed =
-			!is_branch || ycbcr_444_to_420 || ycbcr_420_passthrough;
+			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;
@@ -6885,8 +6932,9 @@ intel_dp_update_420(struct intel_dp *intel_dp)
 	}
 
 	drm_dbg_kms(&i915->drm,
-		    "[CONNECTOR:%d:%s] YCbCr 4:2:0 allowed? %s, YCbCr 4:4:4->4:2:0 conversion? %s\n",
+		    "[CONNECTOR:%d:%s] RGB->YcbCr conversion? %s, YCbCr 4:2:0 allowed? %s, YCbCr 4:4:4->4:2:0 conversion? %s\n",
 		    connector->base.base.id, connector->base.name,
+		    yesno(intel_dp->dfp.rgb_to_ycbcr),
 		    yesno(connector->base.ycbcr_420_allowed),
 		    yesno(intel_dp->dfp.ycbcr_444_to_420));
 }

drivers/gpu/drm/i915/display/intel_dp.h

@@ -51,7 +51,8 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 int intel_dp_retrain_link(struct intel_encoder *encoder,
 			  struct drm_modeset_acquire_ctx *ctx);
 void intel_dp_set_power(struct intel_dp *intel_dp, u8 mode);
-void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp);
+void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
+					   const struct intel_crtc_state *crtc_state);
 void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
 					   const struct intel_crtc_state *crtc_state,
 					   bool enable);