[PATCH v4 5/9] drm/amd/display: Pass up errors reading actual brightness

["Mario Limonciello (AMD)" <superm1@kernel.org>]

[Why]
If the DC API fails to return actual brightness when backlight control
API requests it, then the wrong value may be returned.

[How]
Change return type of amdgpu_dm_backlight_get_level() to an integer
and pass an error code up to the caller.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index c6539e203b92..b6f9188a7b36 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5441,7 +5441,7 @@ static int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
 	return 0;
 }
 
-static u32 amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm,
+static int amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm,
 					 int bl_idx)
 {
 	int ret;
@@ -5455,14 +5455,14 @@ static u32 amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm,
 		u32 avg, peak;
 
 		if (!dc_link_get_backlight_level_nits(link, &avg, &peak))
-			return dm->brightness[bl_idx];
+			return -EINVAL;
 		return convert_brightness_to_user(&caps, avg);
 	}
 
 	ret = dc_link_get_backlight_level(link);
 
 	if (ret == DC_ERROR_UNEXPECTED)
-		return dm->brightness[bl_idx];
+		return -EINVAL;
 
 	return convert_brightness_to_user(&caps, ret);
 }
@@ -5470,7 +5470,7 @@ static u32 amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm,
 static int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd)
 {
 	struct amdgpu_display_manager *dm = bl_get_data(bd);
-	int i;
+	int i, ret;
 
 	for (i = 0; i < dm->num_of_edps; i++) {
 		if (bd == dm->backlight_dev[i])
@@ -5478,7 +5478,12 @@ static int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd)
 	}
 	if (i >= AMDGPU_DM_MAX_NUM_EDP)
 		i = 0;
-	return amdgpu_dm_backlight_get_level(dm, i);
+
+	ret = amdgpu_dm_backlight_get_level(dm, i);
+	if (ret < 0)
+		return dm->brightness[i];
+
+	return ret;
 }
 
 static const struct backlight_ops amdgpu_dm_backlight_ops = {
-- 
2.54.0