[PATCH] drm/amd/display: Avoid using zero AC/DC brightness levels

[Edson Juliano Drosdeck <edson.drosdeck@gmail.com>]

Some systems report zero AC/DC brightness levels during
backlight initialization, causing the panel brightness to
start at the minimum level on boot.

Only use the firmware brightness levels when both AC and DC
values are non-zero

Signed-off-by: Edson Juliano Drosdeck <edson.drosdeck@gmail.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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 5fc5d5608506..f947ce2a8625 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5380,7 +5380,9 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
 	}
 
 	caps = &dm->backlight_caps[aconnector->bl_idx];
-	if (get_brightness_range(caps, &min, &max)) {
+	if (get_brightness_range(caps, &min, &max) &&
+	    caps->ac_level > 0 &&
+	    caps->dc_level > 0) {
 		if (power_supply_is_system_supplied() > 0)
 			props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->ac_level, 100);
 		else
-- 
2.47.3