drm/amdgpu/display: add flag for multi-display mclk switching

Add a dcfeaturemask flag for mclk switching.  Disable by default;
enable once the feature has seen more testing.

Set amdgpu.dcfeaturemask=2 on the kernel command line in grub
to enable this.
Acked-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -694,6 +694,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 	if (amdgpu_dc_feature_mask & DC_FBC_MASK)
 		init_data.flags.fbc_support = true;
 
+	if (amdgpu_dc_feature_mask & DC_MULTI_MON_PP_MCLK_SWITCH_MASK)
+		init_data.flags.multi_mon_pp_mclk_switch = true;
+
 	init_data.flags.power_down_display_on_boot = true;
 
 #ifdef CONFIG_DRM_AMD_DC_DCN2_0

drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c

@@ -3025,7 +3025,10 @@ bool bw_calcs(struct dc_context *ctx,
 
 	populate_initial_data(pipe, pipe_count, data);
 
+	if (ctx->dc->config.multi_mon_pp_mclk_switch)
 		calcs_output->all_displays_in_sync = all_displays_in_sync(pipe, pipe_count);
+	else
+		calcs_output->all_displays_in_sync = false;
 
 	if (data->number_of_displays != 0) {
 		uint8_t yclk_lvl, sclk_lvl;

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

@@ -220,7 +220,7 @@ struct dc_config {
 	bool power_down_display_on_boot;
 	bool edp_not_connected;
 	bool forced_clocks;
-
+	bool multi_mon_pp_mclk_switch;
 };
 
 enum visual_confirm {

drivers/gpu/drm/amd/include/amd_shared.h

@@ -142,6 +142,7 @@ enum PP_FEATURE_MASK {
 
 enum DC_FEATURE_MASK {
 	DC_FBC_MASK = 0x1,
+	DC_MULTI_MON_PP_MCLK_SWITCH_MASK = 0x2,
 };
 
 enum amd_dpm_forced_level;