[PATCH v8 06/14] drm/amd/display: Pass up errors reading actual brightness

[Mario Limonciello <mario.limonciello@amd.com>]

[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>
---
 .../drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c | 13 +++++++++----
 .../drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.h |  2 +-
 .../amdgpu_dm/tests/amdgpu_dm_backlight_test.c      |  4 ++--
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c
index b9e90ea449ca3..406a821d03cd6 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c
@@ -363,7 +363,7 @@ int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
 EXPORT_IF_KUNIT(amdgpu_dm_backlight_update_status);
 
 STATIC_IFN_KUNIT
-u32 amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm, int bl_idx)
+int amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm, int bl_idx)
 {
 	int ret;
 	struct amdgpu_dm_backlight_caps caps;
@@ -376,14 +376,14 @@ u32 amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm, int bl_idx)
 		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);
 }
@@ -394,8 +394,13 @@ int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd)
 {
 	struct amdgpu_display_manager *dm = bl_get_data(bd);
 	int i = amdgpu_dm_backlight_get_device_index(dm, bd);
+	int ret;
+
+	ret = amdgpu_dm_backlight_get_level(dm, i);
+	if (ret < 0)
+		return dm->brightness[i];
 
-	return amdgpu_dm_backlight_get_level(dm, i);
+	return ret;
 }
 EXPORT_IF_KUNIT(amdgpu_dm_backlight_get_brightness);
 
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.h
index 07b75064847c7..72f1c8d861c8c 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.h
@@ -56,7 +56,7 @@ extern const struct attribute_group amdgpu_group;
 struct dc_stream_state *dm_find_stream_with_link(struct amdgpu_display_manager *dm,
 						 struct dc_link *link);
 int amdgpu_dm_backlight_update_status(struct backlight_device *bd);
-u32 amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm, int bl_idx);
+int amdgpu_dm_backlight_get_level(struct amdgpu_display_manager *dm, int bl_idx);
 int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd);
 ssize_t panel_power_savings_show(struct device *device,
 				 struct device_attribute *attr,
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c
index 7ca17f803f9d7..e03173d4e5bd8 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c
@@ -382,7 +382,7 @@ static void dm_test_backlight_get_level_pwm_error(struct kunit *test)
 	dm->brightness[0] = 4321;
 	dm->backlight_link[0] = link;
 
-	KUNIT_EXPECT_EQ(test, amdgpu_dm_backlight_get_level(dm, 0), 4321U);
+	KUNIT_EXPECT_EQ(test, amdgpu_dm_backlight_get_level(dm, 0), -EINVAL);
 }
 
 /**
@@ -424,7 +424,7 @@ static void dm_test_backlight_get_level_aux_error(struct kunit *test)
 	caps->caps_valid = true;
 	caps->aux_support = true;
 
-	KUNIT_EXPECT_EQ(test, amdgpu_dm_backlight_get_level(dm, 0), 6789U);
+	KUNIT_EXPECT_EQ(test, amdgpu_dm_backlight_get_level(dm, 0), -EINVAL);
 }
 
 /**
-- 
2.43.0