drm/amd/display: Use the correct input TF for video formats

[Why]
Color blending for NV12 formats is incorrect because we're using the
predefined SRGB degamma.

[How]
Calculate the correct input transfer function for degamma from the color
module depending on what the actual surface format is.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Zhan Liu <Zhan.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -420,9 +420,21 @@ int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
 {
 	const struct drm_color_lut *degamma_lut;
 	struct dc_plane_state *dc_plane_state = plane->dc_state;
+	enum dc_transfer_func_predefined tf = TRANSFER_FUNCTION_SRGB;
 	uint32_t degamma_size;
 	int r;
 
+	/* Get the correct base transfer function for implicit degamma. */
+	switch (dc_plane_state->format) {
+	case SURFACE_PIXEL_FORMAT_VIDEO_420_YCbCr:
+	case SURFACE_PIXEL_FORMAT_VIDEO_420_YCrCb:
+		/* DC doesn't have a transfer function for BT601 specifically. */
+		tf = TRANSFER_FUNCTION_BT709;
+		break;
+	default:
+		break;
+	}
+
 	if (crtc->cm_has_degamma) {
 		degamma_lut = __extract_blob_lut(crtc->base.degamma_lut,
 						 &degamma_size);
@@ -456,8 +468,7 @@ int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
 		 * map these to the atomic one instead.
 		 */
 		if (crtc->cm_is_degamma_srgb)
-			dc_plane_state->in_transfer_func->tf =
-				TRANSFER_FUNCTION_SRGB;
+			dc_plane_state->in_transfer_func->tf = tf;
 		else
 			dc_plane_state->in_transfer_func->tf =
 				TRANSFER_FUNCTION_LINEAR;
@@ -472,7 +483,12 @@ int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
 		 * in linear space. Assume that the input is sRGB.
 		 */
 		dc_plane_state->in_transfer_func->type = TF_TYPE_PREDEFINED;
-		dc_plane_state->in_transfer_func->tf = TRANSFER_FUNCTION_SRGB;
+		dc_plane_state->in_transfer_func->tf = tf;
+
+		if (tf != TRANSFER_FUNCTION_SRGB &&
+		    !mod_color_calculate_degamma_params(
+			    dc_plane_state->in_transfer_func, NULL, false))
+			return -ENOMEM;
 	} else {
 		/* ...Otherwise we can just bypass the DGM block. */
 		dc_plane_state->in_transfer_func->type = TF_TYPE_BYPASS;