drm/amd/display: Enable 4 to 1 mpc combine for max detile use

In case of certain display configurations we want to allow max detile
buffer utilization by using 4 to 1 mpc combine
Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Reviewed-by: Eric Bernstein <Eric.Bernstein@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -2102,11 +2102,20 @@ int dcn20_populate_dml_pipes_from_context(
 		if (res_ctx->pipe_ctx[i].top_pipe && res_ctx->pipe_ctx[i].top_pipe->plane_state
 				== res_ctx->pipe_ctx[i].plane_state) {
 			struct pipe_ctx *first_pipe = res_ctx->pipe_ctx[i].top_pipe;
+			int split_idx = 0;
 
 			while (first_pipe->top_pipe && first_pipe->top_pipe->plane_state
-					== res_ctx->pipe_ctx[i].plane_state)
+					== res_ctx->pipe_ctx[i].plane_state) {
 				first_pipe = first_pipe->top_pipe;
+				split_idx++;
+			}
+			/* Treat 4to1 mpc combine as an mpo of 2 2-to-1 combines */
+			if (split_idx == 0)
 				pipes[pipe_cnt].pipe.src.hsplit_grp = first_pipe->pipe_idx;
+			else if (split_idx == 1)
+				pipes[pipe_cnt].pipe.src.hsplit_grp = res_ctx->pipe_ctx[i].pipe_idx;
+			else if (split_idx == 2)
+				pipes[pipe_cnt].pipe.src.hsplit_grp = res_ctx->pipe_ctx[i].top_pipe->pipe_idx;
 		} else if (res_ctx->pipe_ctx[i].prev_odm_pipe) {
 			struct pipe_ctx *first_pipe = res_ctx->pipe_ctx[i].prev_odm_pipe;
 
@@ -2258,7 +2267,7 @@ int dcn20_populate_dml_pipes_from_context(
 					|| (res_ctx->pipe_ctx[i].top_pipe && res_ctx->pipe_ctx[i].top_pipe->plane_state == pln)
 					|| pipes[pipe_cnt].pipe.dest.odm_combine != dm_odm_combine_mode_disabled;
 
-			/* stereo is never split, nor odm combine */
+			/* stereo is not split */
 			if (pln->stereo_format == PLANE_STEREO_FORMAT_SIDE_BY_SIDE ||
 			    pln->stereo_format == PLANE_STEREO_FORMAT_TOP_AND_BOTTOM) {
 				pipes[pipe_cnt].pipe.src.is_hsplit = false;
@@ -2721,12 +2730,11 @@ int dcn20_validate_apply_pipe_split_flags(
 		if (!context->res_ctx.pipe_ctx[i].stream)
 			continue;
 
-		if (force_split || v->NoOfDPP[vlevel][max_mpc_comb][pipe_plane] > 1) {
-			if (split4mpc)
+		if (split4mpc || v->NoOfDPP[vlevel][max_mpc_comb][pipe_plane] == 4)
 			split[i] = 4;
-			else
+		else if (force_split || v->NoOfDPP[vlevel][max_mpc_comb][pipe_plane] == 2)
 				split[i] = 2;
-		}
+
 		if ((pipe->stream->view_format ==
 				VIEW_3D_FORMAT_SIDE_BY_SIDE ||
 				pipe->stream->view_format ==