drm/amd/display: Disable dpp root clock when not being used

[Why & How]
Disable root clock for dpp when not being used.
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Agustin Gutierrez Sanchez <agustin.gutierrez@amd.com>
Signed-off-by: Jake Wang <haonan.wang2@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/clk_mgr/dcn31/dcn31_clk_mgr.c

@@ -219,14 +219,17 @@ static void dcn31_update_clocks(struct clk_mgr *clk_mgr_base,
 		update_dispclk = true;
 	}
 
-	/* TODO: add back DTO programming when DPPCLK restore is fixed in FSDL*/
 	if (dpp_clock_lowered) {
 		// increase per DPP DTO before lowering global dppclk
+		dcn20_update_clocks_update_dpp_dto(clk_mgr, context, safe_to_lower);
 		dcn31_smu_set_dppclk(clk_mgr, clk_mgr_base->clks.dppclk_khz);
 	} else {
 		// increase global DPPCLK before lowering per DPP DTO
 		if (update_dppclk || update_dispclk)
 			dcn31_smu_set_dppclk(clk_mgr, clk_mgr_base->clks.dppclk_khz);
+		// always update dtos unless clock is lowered and not safe to lower
+		if (new_clocks->dppclk_khz >= dc->current_state->bw_ctx.bw.dcn.clk.dppclk_khz)
+			dcn20_update_clocks_update_dpp_dto(clk_mgr, context, safe_to_lower);
 	}
 
 	// notify DMCUB of latest clocks

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_dccg.c

@@ -42,6 +42,45 @@
 #define DC_LOGGER \
 	dccg->ctx->logger
 
+static void dccg31_update_dpp_dto(struct dccg *dccg, int dpp_inst, int req_dppclk)
+{
+	struct dcn_dccg *dccg_dcn = TO_DCN_DCCG(dccg);
+
+	if (dccg->ref_dppclk && req_dppclk) {
+		int ref_dppclk = dccg->ref_dppclk;
+		int modulo, phase;
+
+		// phase / modulo = dpp pipe clk / dpp global clk
+		modulo = 0xff;   // use FF at the end
+		phase = ((modulo * req_dppclk) + ref_dppclk - 1) / ref_dppclk;
+
+		if (phase > 0xff) {
+			ASSERT(false);
+			phase = 0xff;
+		}
+
+		REG_SET_2(DPPCLK_DTO_PARAM[dpp_inst], 0,
+				DPPCLK0_DTO_PHASE, phase,
+				DPPCLK0_DTO_MODULO, modulo);
+		REG_UPDATE(DPPCLK_DTO_CTRL,
+				DPPCLK_DTO_ENABLE[dpp_inst], 1);
+	} else {
+		//DTO must be enabled to generate a 0Hz clock output
+		if (dccg->ctx->dc->debug.root_clock_optimization.bits.dpp) {
+			REG_UPDATE(DPPCLK_DTO_CTRL,
+					DPPCLK_DTO_ENABLE[dpp_inst], 1);
+			REG_SET_2(DPPCLK_DTO_PARAM[dpp_inst], 0,
+					DPPCLK0_DTO_PHASE, 0,
+					DPPCLK0_DTO_MODULO, 1);
+		} else {
+			REG_UPDATE(DPPCLK_DTO_CTRL,
+					DPPCLK_DTO_ENABLE[dpp_inst], 0);
+		}
+	}
+	dccg->pipe_dppclk_khz[dpp_inst] = req_dppclk;
+}
+
+
 void dccg31_set_dpstreamclk(
 		struct dccg *dccg,
 		enum hdmistreamclk_source src,
@@ -401,7 +440,7 @@ void dccg31_init(struct dccg *dccg)
 }
 
 static const struct dccg_funcs dccg31_funcs = {
-	.update_dpp_dto = dccg2_update_dpp_dto,
+	.update_dpp_dto = dccg31_update_dpp_dto,
 	.get_dccg_ref_freq = dccg31_get_dccg_ref_freq,
 	.dccg_init = dccg31_init,
 	.set_dpstreamclk = dccg31_set_dpstreamclk,