drm/amd/display: properly turn off unused mpc before front end programming

MPCC_OPP_ID must be programmed to 0xf to properly turn off the mpcc.
However the software state of the mpcc must keep track of the opp that
the mpcc is attached to for reset to properly happen. This is kinda
hacky right now, but a good solution may involve a lot of work.

Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -1572,17 +1572,24 @@ static void dcn10_apply_ctx_for_surface(
 		if ((!pipe_ctx->surface && old_pipe_ctx->surface)
 				|| (!pipe_ctx->stream && old_pipe_ctx->stream)) {
 			struct mpcc_cfg mpcc_cfg;
+			int opp_id_cached = old_pipe_ctx->mpcc->opp_id;
 
 			if (!old_pipe_ctx->top_pipe) {
 				ASSERT(0);
 				continue;
 			}
 
-			mpcc_cfg.opp_id = old_pipe_ctx->mpcc->opp_id;
+			mpcc_cfg.opp_id = 0xf;
 			mpcc_cfg.top_dpp_id = 0xf;
 			mpcc_cfg.bot_mpcc_id = 0xf;
 			mpcc_cfg.top_of_tree = !old_pipe_ctx->top_pipe;
 			old_pipe_ctx->mpcc->funcs->set(old_pipe_ctx->mpcc, &mpcc_cfg);
+			/*
+			 * the mpcc is the only thing that keeps track of the mpcc
+			 * mapping for reset front end right now. Might need some
+			 * rework.
+			 */
+			old_pipe_ctx->mpcc->opp_id = opp_id_cached;
 
 			old_pipe_ctx->top_pipe = NULL;
 			old_pipe_ctx->bottom_pipe = NULL;