drm/amd/display: Fix assert observed when performing dummy p-state check

[WHY]
V.Active dram clock change workaround need a small modification for DMLv2
to ensure that the dummy p-state check doesn't fail.
Signed-off-by: David Galiffi <David.Galiffi@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dcn20/display_mode_vba_20v2.c

@@ -2611,9 +2611,13 @@ static void dml20v2_DISPCLKDPPCLKDCFCLKDeepSleepPrefetchParametersWatermarksAndP
 			mode_lib->vba.MinActiveDRAMClockChangeMargin
 					+ mode_lib->vba.DRAMClockChangeLatency;
 
+
 	if (mode_lib->vba.MinActiveDRAMClockChangeMargin > 50) {
 		mode_lib->vba.DRAMClockChangeWatermark += 25;
 		mode_lib->vba.DRAMClockChangeSupport[0][0] = dm_dram_clock_change_vactive;
+	} else if (mode_lib->vba.DummyPStateCheck &&
+				mode_lib->vba.MinActiveDRAMClockChangeMargin > 0) {
+		mode_lib->vba.DRAMClockChangeSupport[0][0] = dm_dram_clock_change_vactive;
 	} else {
 		if (mode_lib->vba.SynchronizedVBlank || mode_lib->vba.NumberOfActivePlanes == 1) {
 			mode_lib->vba.DRAMClockChangeSupport[0][0] = dm_dram_clock_change_vblank;

drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.c

@@ -222,6 +222,8 @@ static void fetch_socbb_params(struct display_mode_lib *mode_lib)
 	mode_lib->vba.SRExitTime = soc->sr_exit_time_us;
 	mode_lib->vba.SREnterPlusExitTime = soc->sr_enter_plus_exit_time_us;
 	mode_lib->vba.DRAMClockChangeLatency = soc->dram_clock_change_latency_us;
+	mode_lib->vba.DummyPStateCheck = soc->dram_clock_change_latency_us == soc->dummy_pstate_latency_us;
+
 	mode_lib->vba.Downspreading = soc->downspread_percent;
 	mode_lib->vba.DRAMChannelWidth = soc->dram_channel_width_bytes;   // new!
 	mode_lib->vba.FabricDatapathToDCNDataReturn = soc->fabric_datapath_to_dcn_data_return_bytes; // new!

drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.h

@@ -155,6 +155,7 @@ struct vba_vars_st {
 	double UrgentLatencySupportUsChroma;
 	unsigned int DSCFormatFactor;
 
+	bool DummyPStateCheck;
 	bool PrefetchModeSupported;
 	enum self_refresh_affinity AllowDRAMSelfRefreshOrDRAMClockChangeInVblank; // Mode Support only
 	double XFCRemoteSurfaceFlipDelay;