drm/amd/display: Block optimize on consecutive FAMS enables

[WHY]
It is possible to commit state multiple times in rapid succession with
FAMS enabled; if each of these commits were to set optimized_required,
then the user may see latency.

[HOW]
fw_based_mclk_switching is currently not used in dc->clk_mgr; use it
to track whether the current state has FAMS enabled;
if it has, then do not disable FAMS in prepare_bandwidth, and do not set
optimized_required.

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Wesley Chalmers

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

@@ -2117,6 +2117,9 @@ void dcn20_optimize_bandwidth(
 		dc_dmub_srv_p_state_delegate(dc,
 			true, context);
 		context->bw_ctx.bw.dcn.clk.p_state_change_support = true;
+		dc->clk_mgr->clks.fw_based_mclk_switching = true;
+	} else {
+		dc->clk_mgr->clks.fw_based_mclk_switching = false;
 	}
 
 	dc->clk_mgr->funcs->update_clocks(

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c

@@ -983,9 +983,13 @@ void dcn30_set_disp_pattern_generator(const struct dc *dc,
 }
 
 void dcn30_prepare_bandwidth(struct dc *dc,
- 	struct dc_state *context)
+	struct dc_state *context)
 {
-	if (context->bw_ctx.bw.dcn.clk.fw_based_mclk_switching) {
+	bool p_state_change_support = context->bw_ctx.bw.dcn.clk.p_state_change_support;
+	/* Any transition into an FPO config should disable MCLK switching first to avoid
+	 * driver and FW P-State synchronization issues.
+	 */
+	if (context->bw_ctx.bw.dcn.clk.fw_based_mclk_switching || dc->clk_mgr->clks.fw_based_mclk_switching) {
 		dc->optimized_required = true;
 		context->bw_ctx.bw.dcn.clk.p_state_change_support = false;
 	}
@@ -996,7 +1000,19 @@ void dcn30_prepare_bandwidth(struct dc *dc,
 			dc->clk_mgr->funcs->set_max_memclk(dc->clk_mgr, dc->clk_mgr->bw_params->clk_table.entries[dc->clk_mgr->bw_params->clk_table.num_entries - 1].memclk_mhz);
 
 	dcn20_prepare_bandwidth(dc, context);
+	/*
+	 * enabled -> enabled: do not disable
+	 * enabled -> disabled: disable
+	 * disabled -> enabled: don't care
+	 * disabled -> disabled: don't care
+	 */
+	if (!context->bw_ctx.bw.dcn.clk.fw_based_mclk_switching)
+		dc_dmub_srv_p_state_delegate(dc, false, context);
 
-	dc_dmub_srv_p_state_delegate(dc, false, context);
+	if (context->bw_ctx.bw.dcn.clk.fw_based_mclk_switching || dc->clk_mgr->clks.fw_based_mclk_switching) {
+		/* After disabling P-State, restore the original value to ensure we get the correct P-State
+		 * on the next optimize. */
+		context->bw_ctx.bw.dcn.clk.p_state_change_support = p_state_change_support;
+	}
 }