drm/amd/display: Add minimum Z8 residency debug option

[Why]
Allows finer control and tuning for debug and profiling.

[How]
Add the debug option into DC. The default remains the same as before
for now.
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@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

@@ -795,6 +795,7 @@ struct dc_debug_options {
 	unsigned int force_odm_combine; //bit vector based on otg inst
 	unsigned int seamless_boot_odm_combine;
 	unsigned int force_odm_combine_4to1; //bit vector based on otg inst
+	int minimum_z8_residency_time;
 	bool disable_z9_mpc;
 	unsigned int force_fclk_khz;
 	bool enable_tri_buf;

drivers/gpu/drm/amd/display/dc/dcn314/dcn314_resource.c

@@ -887,6 +887,7 @@ static const struct dc_plane_cap plane_cap = {
 static const struct dc_debug_options debug_defaults_drv = {
 	.disable_z10 = false,
 	.enable_z9_disable_interface = true,
+	.minimum_z8_residency_time = 1000,
 	.psr_skip_crtc_disable = true,
 	.disable_dmcu = true,
 	.force_abm_enable = false,

drivers/gpu/drm/amd/display/dc/dml/dcn20/dcn20_fpu.c

@@ -973,7 +973,8 @@ static enum dcn_zstate_support_state  decide_zstate_support(struct dc *dc, struc
 	else if (context->stream_count == 1 &&  context->streams[0]->signal == SIGNAL_TYPE_EDP) {
 		struct dc_link *link = context->streams[0]->sink->link;
 		struct dc_stream_status *stream_status = &context->stream_status[0];
-		bool allow_z8 = context->bw_ctx.dml.vba.StutterPeriod > 1000.0;
+		int minmum_z8_residency = dc->debug.minimum_z8_residency_time > 0 ? dc->debug.minimum_z8_residency_time : 1000;
+		bool allow_z8 = context->bw_ctx.dml.vba.StutterPeriod > (double)minmum_z8_residency;
 		bool is_pwrseq0 = link->link_index == 0;
 
 		if (dc_extended_blank_supported(dc)) {