drm/amd/display: Simplify brightness initialization

[Why]
Remove the brightness cache in DC. It uses a single value to represent
the brightness for both SDR and HDR mode. This leads to flash in HDR
on/off. It also unconditionally programs brightness as in HDR mode. This
may introduce garbage on SDR mode in miniLED panel.

[How]
Simplify the initialization flow by removing the DC cache and taking
what panel has as default. Expand the mechanism for PWM to DPCD Aux to
restore cached brightness value generally.

Cc: stable@vger.kernel.org # 6.1+
Reviewed-by: Krunoslav Kovac <krunoslav.kovac@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Camille Cho <camille.cho@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1610,7 +1610,6 @@ 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;
 
 	struct replay_settings replay_settings;

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

@@ -991,10 +991,6 @@ 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

@@ -879,7 +879,7 @@ 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_cached_brightness_aux(link);
+			set_default_brightness_aux(link);
 		}
 
 		return true;

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

@@ -2142,8 +2142,7 @@ 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_cached_brightness_aux(link);
-
+		set_default_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

@@ -170,7 +170,6 @@ 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,
@@ -288,9 +287,9 @@ bool set_default_brightness_aux(struct dc_link *link)
 	if (link && link->dpcd_sink_ext_caps.bits.oled == 1) {
 		if (!read_default_bl_aux(link, &default_backlight))
 			default_backlight = 150000;
-		// if < 1 nits or > 5000, it might be wrong readback
-		if (default_backlight < 1000 || default_backlight > 5000000)
-			default_backlight = 150000; //
+		// if > 5000, it might be wrong readback
+		if (default_backlight > 5000000)
+			default_backlight = 150000;
 
 		return edp_set_backlight_level_nits(link, true,
 				default_backlight, 0);
@@ -298,15 +297,6 @@ 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_enabled(struct dc_link *link)
 {
 	if (link->dpcd_caps.edp_supported_link_rates_count == 0 || !link->panel_config.ilr.optimize_edp_link_rate)

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

@@ -30,7 +30,6 @@
 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,