drm/amd/display: Enabling eDP no power sequencing with DAL feature mask

[Why]
Sometimes, DP receiver chip power-controlled externally by an
Embedded Controller could be treated and used as eDP,
if it drives mobile display. In this case,
we shouldn't be doing power-sequencing, hence we can skip
waiting for T7-ready and T9-ready."

[How]
Added a feature mask to enable eDP no power sequencing feature.

To enable this, set 0x10 flag in amdgpu.dcfeaturemask on
Linux command line.

Signed-off-by: Zhan Liu <zhan.liu@amd.com>
Reviewed-by: Nikola Cornij <Nikola.Cornij@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

@@ -160,6 +160,7 @@ int amdgpu_smu_pptable_id = -1;
  *     highest. That helps saving some idle power.
  * DISABLE_FRACTIONAL_PWM (bit 2) disabled by default
  * PSR (bit 3) disabled by default
+ * EDP NO POWER SEQUENCING (bit 4) disabled by default
  */
 uint amdgpu_dc_feature_mask = 2;
 uint amdgpu_dc_debug_mask;

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -1160,6 +1160,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 	if (amdgpu_dc_feature_mask & DC_DISABLE_FRACTIONAL_PWM_MASK)
 		init_data.flags.disable_fractional_pwm = true;
 
+	if (amdgpu_dc_feature_mask & DC_EDP_NO_POWER_SEQUENCING)
+		init_data.flags.edp_no_power_sequencing = true;
+
 	init_data.flags.power_down_display_on_boot = true;
 
 	INIT_LIST_HEAD(&adev->dm.da_list);

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

@@ -297,6 +297,7 @@ struct dc_config {
 	bool allow_seamless_boot_optimization;
 	bool power_down_display_on_boot;
 	bool edp_not_connected;
+	bool edp_no_power_sequencing;
 	bool force_enum_edp;
 	bool forced_clocks;
 	bool allow_lttpr_non_transparent_mode;

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -1022,8 +1022,20 @@ void dce110_edp_backlight_control(
 	/* dc_service_sleep_in_milliseconds(50); */
 		/*edp 1.2*/
 	panel_instance = link->panel_cntl->inst;
-	if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_ON)
-		edp_receiver_ready_T7(link);
+
+	if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_ON) {
+		if (!link->dc->config.edp_no_power_sequencing)
+		/*
+		 * Sometimes, DP receiver chip power-controlled externally by an
+		 * Embedded Controller could be treated and used as eDP,
+		 * if it drives mobile display. In this case,
+		 * we shouldn't be doing power-sequencing, hence we can skip
+		 * waiting for T7-ready.
+		 */
+			edp_receiver_ready_T7(link);
+		else
+			DC_LOG_DC("edp_receiver_ready_T7 skipped\n");
+	}
 
 	if (ctx->dc->ctx->dmub_srv &&
 			ctx->dc->debug.dmub_command_table) {
@@ -1048,8 +1060,19 @@ void dce110_edp_backlight_control(
 		dc_link_backlight_enable_aux(link, enable);
 
 	/*edp 1.2*/
-	if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_OFF)
-		edp_add_delay_for_T9(link);
+	if (cntl.action == TRANSMITTER_CONTROL_BACKLIGHT_OFF) {
+		if (!link->dc->config.edp_no_power_sequencing)
+		/*
+		 * Sometimes, DP receiver chip power-controlled externally by an
+		 * Embedded Controller could be treated and used as eDP,
+		 * if it drives mobile display. In this case,
+		 * we shouldn't be doing power-sequencing, hence we can skip
+		 * waiting for T9-ready.
+		 */
+			edp_add_delay_for_T9(link);
+		else
+			DC_LOG_DC("edp_receiver_ready_T9 skipped\n");
+	}
 
 	if (!enable && link->dpcd_sink_ext_caps.bits.oled)
 		msleep(OLED_PRE_T11_DELAY);

drivers/gpu/drm/amd/include/amd_shared.h

@@ -223,10 +223,12 @@ enum amd_harvest_ip_mask {
 };
 
 enum DC_FEATURE_MASK {
-	DC_FBC_MASK = 0x1,
-	DC_MULTI_MON_PP_MCLK_SWITCH_MASK = 0x2,
-	DC_DISABLE_FRACTIONAL_PWM_MASK = 0x4,
-	DC_PSR_MASK = 0x8,
+	//Default value can be found at "uint amdgpu_dc_feature_mask"
+	DC_FBC_MASK = (1 << 0), //0x1, disabled by default
+	DC_MULTI_MON_PP_MCLK_SWITCH_MASK = (1 << 1), //0x2, enabled by default
+	DC_DISABLE_FRACTIONAL_PWM_MASK = (1 << 2), //0x4, disabled by default
+	DC_PSR_MASK = (1 << 3), //0x8, disabled by default
+	DC_EDP_NO_POWER_SEQUENCING = (1 << 4), //0x10, disabled by default
 };
 
 enum DC_DEBUG_MASK {