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

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

On 5/26/26 22:00, Edson Juliano Drosdeck wrote:
> 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>

Can you please share an acpidump and an EDID into a bug report to look at?

> ---
>   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