drm/amd/display: Update TTU properly

[Why]
We need to update TTU properly if DRAMClockChangeWatermark changes. If
TTU < DRAMClockChangeWatermark, we pstate won't be allowed and we will
hang in some PSR cases.

[How]
Update TTU if DramClockChangeWatermark value increases (only if TTU was
dependent on the watermark value on the DRAMClockChangeWatermark value
in the first place).
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@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/dml/dcn20/display_mode_vba_20v2.c

@@ -2614,6 +2614,14 @@ static void dml20v2_DISPCLKDPPCLKDCFCLKDeepSleepPrefetchParametersWatermarksAndP
 
 	if (mode_lib->vba.DRAMClockChangeSupportsVActive &&
 			mode_lib->vba.MinActiveDRAMClockChangeMargin > 60) {
+
+		for (k = 0; k < mode_lib->vba.NumberOfActivePlanes; ++k) {
+			if (mode_lib->vba.PrefetchMode[mode_lib->vba.VoltageLevel][mode_lib->vba.maxMpcComb] == 0) {
+				if (mode_lib->vba.DRAMClockChangeWatermark >
+				dml_max(mode_lib->vba.StutterEnterPlusExitWatermark, mode_lib->vba.UrgentWatermark))
+					mode_lib->vba.MinTTUVBlank[k] += 25;
+			}
+		}
 		mode_lib->vba.DRAMClockChangeWatermark += 25;
 		mode_lib->vba.DRAMClockChangeSupport[0][0] = dm_dram_clock_change_vactive;
 	} else if (mode_lib->vba.DummyPStateCheck &&