Brightness stuck at 100% on Zephyrus G16 Ubuntu 24.04 LTS

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1

Ubuntu Version

Ubuntu 24.04 LTS

Desktop Environment

GNOME

Problem Description

I am unable to adjust the internal display brightness on my ASUS ROG Zephyrus G16.

The brightness slider in GNOME moves normally, and the brightness indicator appears when I press the brightness function keys. However, the actual OLED display brightness does not change.

The issue can be reproduced with the following steps:

  1. Open Settings.

  2. Go to Power or use the brightness slider in the system menu.

  3. Move the brightness slider to a lower or higher value.

  4. The slider value changes, but the physical screen brightness remains unchanged.

The same thing happens when using the keyboard brightness keys.

Relevant System Information

Laptop:

ASUS ROG Zephyrus G16
CPU: Intel Core Ultra 9
GPU: Intel integrated graphics and NVIDIA RTX 4060 max-q
Display: Internal OLED display

I cannot currently provide the exact laptop model, kernel version, driver details, or command outputs because I do not have access to the laptop at the moment.

I found reports of a similar issue on the same or a similar laptop model:

However, those reports mainly involve Fedora or Arch Linux, while I am using Ubuntu.

One of the references also mentions asusctl, but I have not installed it because Ubuntu is not officially supported by the ASUS Linux project. I am also unsure whether asusctl would affect the OLED panel brightness or only ASUS-specific features such as GPU modes, power profiles, fan control, keyboard lighting, and battery charge limits.

What I’ve Tried

I have already tried the following:

  1. Installing the NVIDIA driver through Software Updater.

  2. Installing the recommended Ubuntu NVIDIA driver using: sudo ubuntu-drivers install

  3. Installing an NVIDIA driver directly from the NVIDIA website.

  4. Using brightnessctl.

  5. Changing brightness values manually through /sys/class/backlight.

  6. Adding the following kernel parameter: i915.enable_dpcd_backlight=1

  7. Testing the following GRUB configuration:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_dpcd_backlight=1 nvidia.NVreg_EnableBacklightHandler=0 nvidia.NVreg_RegistryDwords=EnableBrightnessControl=0"
  1. Trying different NVIDIA installation methods, including Software Updater, ubuntu-drivers, and the installer from the NVIDIA website.

None of these methods change the actual display brightness, and actually before using ubuntu I used pop os and experienced the same thing.

Has anyone successfully fixed brightness control on an ASUS ROG Zephyrus G16 with an Intel Core Ultra processor and OLED display under Ubuntu?

2

For the GRUB configuration, try these:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=native"

and

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_iommu=off"

and both together

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=native intel_iommu=off"

If none of those works, sorry, I have no further suggestions.

EDIT: Which kernel version are you using?

uname --all
3

I already tried that solution, but it still does not work.

My kernel version:
Linux adam-pc 7.0.0-28-generic #28-Ubuntu SMP PREEMPT_DYNAMIC Sun Jun 21 01:01:36 UTC 2026 x86_64 GNU/Linux

4

That’s interesting.

Did the other suggestions help at all?

5

I eventually moved from Ubuntu to Fedora, since the issue still persisted on both Ubuntu and Pop OS, and unfortunately I encountered the same brightness problem on Fedora as well.

On Fedora, I checked which GPU was actually driving the internal display. The internal eDP-1 panel was connected to the Intel iGPU using the i915 driver, not directly to the NVIDIA RTX GPU.

I initially used:

i915.enable_dpcd_backlight=1

but the brightness value changed only in /sys/class/backlight/intel_backlight/ and the physical screen brightness did not change.

Then I checked the kernel log and found this message:

Panel is missing HDR static metadata. Possible support for Intel HDR backlight interface is not used. If your backlight controls don't work try booting with i915.enable_dpcd_backlight=3.

So I changed the parameter from 1 to:

i915.enable_dpcd_backlight=3

The reason is that value 1 enables DPCD backlight support but still lets the driver choose the backlight interface automatically. In my case, the panel did not expose the HDR static metadata expected by the driver, so the correct Intel backlight interface was not selected.

Value 3 forces the Intel DPCD/HDR backlight interface, and after rebooting, the brightness controls finally started working.

So the other suggestions helped with the diagnosis, but the actual fix was confirming that the display was driven by i915, and changing i915.enable_dpcd_backlight=1 to i915.enable_dpcd_backlight=3.

This approach may also work on Ubuntu, as long as the internal display is driven by the Intel i915 driver and the kernel shows a similar message about missing HDR static metadata.

1 Like
6

I can confirm that this solution works on Ubuntu 26.04 running on ASUS Zephyrus G16 2025 (Intel iGPU + NVIDIA dGPU). Thanks for sharing your findings!

For anyone who wants the quick steps:

  1. Edit GRUB:
    sudo nano /etc/default/grub
  2. Set:
    GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_dpcd_backlight=3"
  3. Apply and reboot:
    sudo update-grub
    reboot
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