drm/amdgpu/display: handle aux backlight in backlight_get_brightness

Need to fetch it via aux.
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -3343,11 +3343,27 @@ static int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
 static int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd)
 {
 	struct amdgpu_display_manager *dm = bl_get_data(bd);
-	int ret = dc_link_get_backlight_level(dm->backlight_link);
+	struct amdgpu_dm_backlight_caps caps;
+
+	amdgpu_dm_update_backlight_caps(dm);
+	caps = dm->backlight_caps;
 
-	if (ret == DC_ERROR_UNEXPECTED)
-		return bd->props.brightness;
-	return convert_brightness_to_user(&dm->backlight_caps, ret);
+	if (caps.aux_support) {
+		struct dc_link *link = (struct dc_link *)dm->backlight_link;
+		u32 avg, peak;
+		bool rc;
+
+		rc = dc_link_get_backlight_level_nits(link, &avg, &peak);
+		if (!rc)
+			return bd->props.brightness;
+		return convert_brightness_to_user(&caps, avg);
+	} else {
+		int ret = dc_link_get_backlight_level(dm->backlight_link);
+
+		if (ret == DC_ERROR_UNEXPECTED)
+			return bd->props.brightness;
+		return convert_brightness_to_user(&caps, ret);
+	}
 }
 
 static const struct backlight_ops amdgpu_dm_backlight_ops = {