drm/amd/display: Cache backlight_millinits in link structure and setting brightness accordingly

[Why]
Need to save the cached backlight level so that display lights up using
appropriate brightness level instead of the default brightness when
waking up from s0i3.

[How]
Adding a backlight level cache in link structure. Also instead on
calling set_default_brightness_aux, check if cached values exists.
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: Nicholas Susanto <nicholas.susanto@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/dc.h

@@ -1515,6 +1515,7 @@ struct dc_link {
 	enum edp_revision edp_revision;
 	union dpcd_sink_ext_caps dpcd_sink_ext_caps;
 
+	struct backlight_settings backlight_settings;
 	struct psr_settings psr_settings;
 
 	/* Drive settings read from integrated info table */

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

@@ -994,6 +994,10 @@ struct link_mst_stream_allocation_table {
 	struct link_mst_stream_allocation stream_allocations[MAX_CONTROLLER_NUM];
 };
 
+struct backlight_settings {
+	uint32_t backlight_millinits;
+};
+
 /* PSR feature flags */
 struct psr_settings {
 	bool psr_feature_enabled;		// PSR is supported by sink

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

@@ -876,8 +876,7 @@ static bool detect_link_and_local_sink(struct dc_link *link,
 			(link->dpcd_sink_ext_caps.bits.oled == 1)) {
 			dpcd_set_source_specific_data(link);
 			msleep(post_oui_delay);
-			set_default_brightness_aux(link);
-			//TODO: use cached
+			set_cached_brightness_aux(link);
 		}
 
 		return true;

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

@@ -2136,7 +2136,8 @@ static enum dc_status enable_link_dp(struct dc_state *state,
 	if (link->dpcd_sink_ext_caps.bits.oled == 1 ||
 		link->dpcd_sink_ext_caps.bits.sdr_aux_backlight_control == 1 ||
 		link->dpcd_sink_ext_caps.bits.hdr_aux_backlight_control == 1) {
-		set_default_brightness_aux(link); // TODO: use cached if known
+		set_cached_brightness_aux(link);
+
 		if (link->dpcd_sink_ext_caps.bits.oled == 1)
 			msleep(bl_oled_enable_delay);
 		edp_backlight_enable_aux(link, true);

drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c

@@ -164,6 +164,7 @@ bool edp_set_backlight_level_nits(struct dc_link *link,
 	*(uint32_t *)&dpcd_backlight_set.backlight_level_millinits = backlight_millinits;
 	*(uint16_t *)&dpcd_backlight_set.backlight_transition_time_ms = (uint16_t)transition_time_in_ms;
 
+	link->backlight_settings.backlight_millinits = backlight_millinits;
 
 	if (!link->dpcd_caps.panel_luminance_control) {
 		if (core_link_write_dpcd(link, DP_SOURCE_BACKLIGHT_LEVEL,
@@ -276,6 +277,16 @@ bool set_default_brightness_aux(struct dc_link *link)
 	return false;
 }
 
+bool set_cached_brightness_aux(struct dc_link *link)
+{
+	if (link->backlight_settings.backlight_millinits)
+		return edp_set_backlight_level_nits(link, true,
+						    link->backlight_settings.backlight_millinits, 0);
+	else
+		return set_default_brightness_aux(link);
+	return false;
+}
+
 bool edp_is_ilr_optimization_required(struct dc_link *link,
 		struct dc_crtc_timing *crtc_timing)
 {

drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.h

@@ -30,6 +30,7 @@
 enum dp_panel_mode dp_get_panel_mode(struct dc_link *link);
 void dp_set_panel_mode(struct dc_link *link, enum dp_panel_mode panel_mode);
 bool set_default_brightness_aux(struct dc_link *link);
+bool set_cached_brightness_aux(struct dc_link *link);
 void edp_panel_backlight_power_on(struct dc_link *link, bool wait_for_hpd);
 int edp_get_backlight_level(const struct dc_link *link);
 bool edp_get_backlight_level_nits(struct dc_link *link,