drm/amd/display: Improvement for handling edp link training fails

[Why]
The eDP retrain will cause the DPCD 300 to be reset to default.
And cause the brightness can't be set correctly.

[How]
delete the call to edp panel power control in both
enable_link_output/disable_link_output entirely and
only call edp panel control in enable_link_dp and 
disable_link_dp once.

Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Jingwen Zhu <Jingwen.Zhu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Zhu-Jingwen

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

@@ -3031,10 +3031,12 @@ void dce110_enable_dp_link_output(
 	const struct link_hwss *link_hwss = get_link_hwss(link, link_res);
 	unsigned int i;
 
-
+	/*
+	 * Add the logic to extract BOTH power up and power down sequences
+	 * from enable/disable link output and only call edp panel control
+	 * in enable_link_dp and disable_link_dp once.
+	 */
 	if (link->connector_signal == SIGNAL_TYPE_EDP) {
-		if (!link->dc->config.edp_no_power_sequencing)
-			link->dc->hwss.edp_power_control(link, true);
 		link->dc->hwss.edp_wait_for_hpd_ready(link, true);
 	}
 
@@ -3096,11 +3098,12 @@ void dce110_disable_link_output(struct dc_link *link,
 
 	link_hwss->disable_link_output(link, link_res, signal);
 	link->phy_state.symclk_state = SYMCLK_OFF_TX_OFF;
-
-	if (signal == SIGNAL_TYPE_EDP &&
-			link->dc->hwss.edp_backlight_control)
-		link->dc->hwss.edp_power_control(link, false);
-	else if (dmcu != NULL && dmcu->funcs->lock_phy)
+	/*
+	 * Add the logic to extract BOTH power up and power down sequences
+	 * from enable/disable link output and only call edp panel control
+	 * in enable_link_dp and disable_link_dp once.
+	 */
+	if (dmcu != NULL && dmcu->funcs->lock_phy)
 		dmcu->funcs->unlock_phy(dmcu);
 	dc->link_srv->dp_trace_source_sequence(link, DPCD_SOURCE_SEQ_AFTER_DISABLE_LINK_PHY);
 }

drivers/gpu/drm/amd/display/dc/link/link_dpms.c

@@ -1927,6 +1927,11 @@ static void disable_link_dp(struct dc_link *link,
 
 	dp_disable_link_phy(link, link_res, signal);
 
+	if (link->connector_signal == SIGNAL_TYPE_EDP) {
+		if (!link->dc->config.edp_no_power_sequencing)
+			link->dc->hwss.edp_power_control(link, false);
+	}
+
 	if (signal == SIGNAL_TYPE_DISPLAY_PORT_MST)
 		/* set the sink to SST mode after disabling the link */
 		enable_mst_on_sink(link, false);