drm/amd/display: Allow Z8 when stutter threshold is not met for dcn35

[Why&How]
Some panels don't meet the stutter threshold (4k etc), this leads to
power regressions. Allow z8 for panels that don't meet the threshold
but support PSR/replay
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Bhawanpreet Lakha <bhawanpreet.lakha@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/dml/dcn35/dcn35_fpu.c

@@ -603,7 +603,7 @@ void dcn35_decide_zstate_support(struct dc *dc, struct dc_state *context)
 		if (is_pwrseq0 && allow_z10)
 			support = DCN_ZSTATE_SUPPORT_ALLOW;
 		else if (is_pwrseq0 && (is_psr || is_replay))
-			support = allow_z8 ? DCN_ZSTATE_SUPPORT_ALLOW_Z8_Z10_ONLY : DCN_ZSTATE_SUPPORT_ALLOW_Z10_ONLY;
+			support = DCN_ZSTATE_SUPPORT_ALLOW_Z8_Z10_ONLY;
 		else if (allow_z8)
 			support = DCN_ZSTATE_SUPPORT_ALLOW_Z8_ONLY;
 

drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c

@@ -570,6 +570,7 @@ static bool dml2_validate_and_build_resource(const struct dc *in_dc, struct dc_s
 	struct dml2_dcn_clocks out_clks;
 	unsigned int result = 0;
 	bool need_recalculation = false;
+	uint32_t cstate_enter_plus_exit_z8_ns;
 
 	if (!context || context->stream_count == 0)
 		return true;
@@ -641,6 +642,14 @@ static bool dml2_validate_and_build_resource(const struct dc *in_dc, struct dc_s
 		dml2_extract_watermark_set(&context->bw_ctx.bw.dcn.watermarks.d, &dml2->v20.dml_core_ctx);
 		//copy for deciding zstate use
 		context->bw_ctx.dml.vba.StutterPeriod = context->bw_ctx.dml2->v20.dml_core_ctx.mp.StutterPeriod;
+
+		cstate_enter_plus_exit_z8_ns = context->bw_ctx.bw.dcn.watermarks.a.cstate_pstate.cstate_enter_plus_exit_z8_ns;
+
+		if (context->bw_ctx.dml.vba.StutterPeriod < in_dc->debug.minimum_z8_residency_time &&
+				cstate_enter_plus_exit_z8_ns < in_dc->debug.minimum_z8_residency_time * 1000)
+			cstate_enter_plus_exit_z8_ns = in_dc->debug.minimum_z8_residency_time * 1000;
+
+		context->bw_ctx.bw.dcn.watermarks.a.cstate_pstate.cstate_enter_plus_exit_z8_ns = cstate_enter_plus_exit_z8_ns;
 	}
 
 	return result;