drm/amd/display: add debug option for ExtendedVBlank DLG adjust

[why & how]
Add new option for debug usage
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Muhammad Ahmed <ahmed.ahmed@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -979,6 +979,7 @@ struct dc_debug_options {
 	unsigned int ips2_eval_delay_us;
 	unsigned int ips2_entry_delay_us;
 	bool disable_timeout;
+	bool disable_extblankadj;
 };
 
 struct gpu_info_soc_bounding_box_v1_0;

drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c

@@ -2221,7 +2221,8 @@ void dcn20_optimize_bandwidth(
 			dc->clk_mgr,
 			context,
 			true);
-	if (context->bw_ctx.bw.dcn.clk.zstate_support == DCN_ZSTATE_SUPPORT_ALLOW) {
+	if (context->bw_ctx.bw.dcn.clk.zstate_support == DCN_ZSTATE_SUPPORT_ALLOW &&
+		!dc->debug.disable_extblankadj) {
 		for (i = 0; i < dc->res_pool->pipe_count; ++i) {
 			struct pipe_ctx *pipe_ctx = &context->res_ctx.pipe_ctx[i];