drm/amd/display: take dpms_off into account for edp turn off logic

[why]
Previously we incorrectly skipped backlight control when stream is
present but dpms_off = true. This causes backlight to remain on in
the we boot up or resume into a external display only configuration
where VBIOS posted on the eDP.

[How]
Add dpms_off into the condition for edp need to turn off.

Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Reviewed-by: Yongqiang Sun <yongqiang.sun@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1520,7 +1520,7 @@ static struct dc_link *get_link_for_edp(struct dc *dc)
 	return NULL;
 }
 
-static struct dc_link *get_link_for_edp_not_in_use(
+static struct dc_link *get_link_for_edp_to_turn_off(
 		struct dc *dc,
 		struct dc_state *context)
 {
@@ -1529,8 +1529,12 @@ static struct dc_link *get_link_for_edp_not_in_use(
 
 	/* check if eDP panel is suppose to be set mode, if yes, no need to disable */
 	for (i = 0; i < context->stream_count; i++) {
-		if (context->streams[i]->signal == SIGNAL_TYPE_EDP)
-			return NULL;
+		if (context->streams[i]->signal == SIGNAL_TYPE_EDP) {
+			if (context->streams[i]->dpms_off == true)
+				return context->streams[i]->sink->link;
+			else
+				return NULL;
+		}
 	}
 
 	/* check if there is an eDP panel not in use */
@@ -1572,7 +1576,7 @@ void dce110_enable_accelerated_mode(struct dc *dc, struct dc_state *context)
 	}
 
 	if (can_edp_fast_boot_optimize)
-		edp_link_to_turnoff = get_link_for_edp_not_in_use(dc, context);
+		edp_link_to_turnoff = get_link_for_edp_to_turn_off(dc, context);
 
 	/* if OS doesn't light up eDP and eDP link is available, we want to disable
 	 * If resume from S4/S5, should optimization.