From: Anthony Koo <Anthony.Koo@amd.com>
Date: Thu, 15 Mar 2018 14:54:30 -0400
Subject: drm/amd/display: Only program MSA_TIMING_PARAM if it changed
Git-commit: 87943159f4093d2dae22abccbe046dac0fbdad4f
Patch-mainline: v4.18-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -1183,16 +1183,21 @@ static void enable_stream_features(struc
 {
 	struct dc_stream_state *stream = pipe_ctx->stream;
 	struct dc_link *link = stream->sink->link;
-	union down_spread_ctrl downspread;
+	union down_spread_ctrl old_downspread;
+	union down_spread_ctrl new_downspread;
 
 	core_link_read_dpcd(link, DP_DOWNSPREAD_CTRL,
-			&downspread.raw, sizeof(downspread));
+			&old_downspread.raw, sizeof(old_downspread));
 
-	downspread.bits.IGNORE_MSA_TIMING_PARAM =
+	new_downspread.raw = old_downspread.raw;
+
+	new_downspread.bits.IGNORE_MSA_TIMING_PARAM =
 			(stream->ignore_msa_timing_param) ? 1 : 0;
 
-	core_link_write_dpcd(link, DP_DOWNSPREAD_CTRL,
-			&downspread.raw, sizeof(downspread));
+	if (new_downspread.raw != old_downspread.raw) {
+		core_link_write_dpcd(link, DP_DOWNSPREAD_CTRL,
+			&new_downspread.raw, sizeof(new_downspread));
+	}
 }
 
 static enum dc_status enable_link_dp(