drm/i915/dg2: use 128b/132b transcoder DDI mode

128b/132b has a separate transcoder DDI mode, which also requires the
MST transport select to be set. Note that we'll use DP MST also for
single-stream 128b/132b.

Having the FDI and 128b/132b modes share the register mode value
complicates things a bit.

v2:
- Use HAS_DP20 abstraction for 128b/132b mode (Ville)
- Use intel_dp_is_uhbr() helper

Bspec: 50493
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/279bfbd979e0256fae13a5231e07e2f4fb665c07.1631191763.git.jani.nikula@intel.com

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

@@ -506,7 +506,10 @@ intel_ddi_transcoder_func_reg_val_get(struct intel_encoder *encoder,
 		temp |= TRANS_DDI_MODE_SELECT_FDI_OR_128B132B;
 		temp |= (crtc_state->fdi_lanes - 1) << 1;
 	} else if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST)) {
-		temp |= TRANS_DDI_MODE_SELECT_DP_MST;
+		if (intel_dp_is_uhbr(crtc_state))
+			temp |= TRANS_DDI_MODE_SELECT_FDI_OR_128B132B;
+		else
+			temp |= TRANS_DDI_MODE_SELECT_DP_MST;
 		temp |= DDI_PORT_WIDTH(crtc_state->lane_count);
 
 		if (DISPLAY_VER(dev_priv) >= 12) {
@@ -694,7 +697,12 @@ bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector)
 		break;
 
 	case TRANS_DDI_MODE_SELECT_FDI_OR_128B132B:
-		ret = type == DRM_MODE_CONNECTOR_VGA;
+		if (HAS_DP20(dev_priv))
+			/* 128b/132b */
+			ret = false;
+		else
+			/* FDI */
+			ret = type == DRM_MODE_CONNECTOR_VGA;
 		break;
 
 	default:
@@ -781,8 +789,9 @@ static void intel_ddi_get_encoder_pipes(struct intel_encoder *encoder,
 		if ((tmp & port_mask) != ddi_select)
 			continue;
 
-		if ((tmp & TRANS_DDI_MODE_SELECT_MASK) ==
-		    TRANS_DDI_MODE_SELECT_DP_MST)
+		if ((tmp & TRANS_DDI_MODE_SELECT_MASK) == TRANS_DDI_MODE_SELECT_DP_MST ||
+		    (HAS_DP20(dev_priv) &&
+		     (tmp & TRANS_DDI_MODE_SELECT_MASK) == TRANS_DDI_MODE_SELECT_FDI_OR_128B132B))
 			mst_pipe_mask |= BIT(p);
 
 		*pipe_mask |= BIT(p);
@@ -3573,9 +3582,6 @@ static void intel_ddi_read_func_ctl(struct intel_encoder *encoder,
 		pipe_config->output_types |= BIT(INTEL_OUTPUT_HDMI);
 		pipe_config->lane_count = 4;
 		break;
-	case TRANS_DDI_MODE_SELECT_FDI_OR_128B132B:
-		pipe_config->output_types |= BIT(INTEL_OUTPUT_ANALOG);
-		break;
 	case TRANS_DDI_MODE_SELECT_DP_SST:
 		if (encoder->type == INTEL_OUTPUT_EDP)
 			pipe_config->output_types |= BIT(INTEL_OUTPUT_EDP);
@@ -3604,6 +3610,13 @@ static void intel_ddi_read_func_ctl(struct intel_encoder *encoder,
 			pipe_config->infoframes.enable |=
 				intel_hdmi_infoframes_enabled(encoder, pipe_config);
 		break;
+	case TRANS_DDI_MODE_SELECT_FDI_OR_128B132B:
+		if (!HAS_DP20(dev_priv)) {
+			/* FDI */
+			pipe_config->output_types |= BIT(INTEL_OUTPUT_ANALOG);
+			break;
+		}
+		fallthrough; /* 128b/132b */
 	case TRANS_DDI_MODE_SELECT_DP_MST:
 		pipe_config->output_types |= BIT(INTEL_OUTPUT_DP_MST);
 		pipe_config->lane_count =