drm/amd/display: Wrong colorimetry workaround

[Why]
For FreeSync HDR, native color space flag in AMD VSIF(BT.709) should be
used when intepreting content and color space flag in VSC or AVI
infoFrame should be ignored. However, it turned out some userspace
application still use color flag in VSC or AVI infoFrame which is
incorrect.

[How]
Transfer function is used when building the VSC and AVI infoFrame. Set
colorimetry to BT.709 when all the following match:

1. Pixel format is YCbCr;
2. In FreeSync 2 HDR, color is COLOR_SPACE_2020_YCBCR;
3. Transfer function is TRANSFER_FUNC_GAMMA_22;

Tested-by: Mark Broadworth <[e-mail]>
Reviewed-by: Krunoslav Kovac <[e-mail]>
Acked-by: Rodrigo Siqueira <[e-mail]>
Signed-off-by: Ma Hanghong <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

···
 	bool scale = dm_state ? (dm_state->scaling != RMX_OFF) : false;
 	int mode_refresh;
 	int preferred_refresh = 0;
+	enum color_transfer_func tf = TRANSFER_FUNC_UNKNOWN;
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	struct dsc_dec_dpcd_caps dsc_caps;
 #endif
···
 			if (stream->link->dpcd_caps.dprx_feature.bits.VSC_SDP_COLORIMETRY_SUPPORTED)
 				stream->use_vsc_sdp_for_colorimetry = true;
 		}
-		mod_build_vsc_infopacket(stream, &stream->vsc_infopacket, stream->output_color_space);
+		if (stream->out_transfer_func->tf == TRANSFER_FUNCTION_GAMMA22)
+			tf = TRANSFER_FUNC_GAMMA_22;
+		mod_build_vsc_infopacket(stream, &stream->vsc_infopacket, stream->output_color_space, tf);
 		aconnector->psr_skip_count = AMDGPU_DM_PSR_ENTRY_DELAY;
 
 	}

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

···
 		hdmi_info.bits.C0_C1   = COLORIMETRY_EXTENDED;
 	}
 
+	if (pixel_encoding && color_space == COLOR_SPACE_2020_YCBCR &&
+			stream->out_transfer_func->tf == TRANSFER_FUNCTION_GAMMA22) {
+		hdmi_info.bits.EC0_EC2 = 0;
+		hdmi_info.bits.C0_C1 = COLORIMETRY_ITU709;
+	}
+
 	/* TODO: un-hardcode aspect ratio */
 	aspect = stream->timing.aspect_ratio;
 

drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h

···
 
 void mod_build_vsc_infopacket(const struct dc_stream_state *stream,
 		struct dc_info_packet *info_packet,
-		enum dc_color_space cs);
+		enum dc_color_space cs,
+		enum color_transfer_func tf);
 
 void mod_build_hf_vsif_infopacket(const struct dc_stream_state *stream,
 		struct dc_info_packet *info_packet);

drivers/gpu/drm/amd/display/modules/info_packet/info_packet.c

···
 
 void mod_build_vsc_infopacket(const struct dc_stream_state *stream,
 		struct dc_info_packet *info_packet,
-		enum dc_color_space cs)
+		enum dc_color_space cs,
+		enum color_transfer_func tf)
 {
 	unsigned int vsc_packet_revision = vsc_packet_undefined;
 	unsigned int i;
···
 				colorimetryFormat = ColorimetryYCC_DP_AdobeYCC;
 			else if (cs == COLOR_SPACE_2020_YCBCR)
 				colorimetryFormat = ColorimetryYCC_DP_ITU2020YCbCr;
+
+			if (cs == COLOR_SPACE_2020_YCBCR && tf == TRANSFER_FUNC_GAMMA_22)
+				colorimetryFormat = ColorimetryYCC_DP_ITU709;
 			break;
 
 		default: