[Dell XPS 15 9570] Unable to change laptop screen brightness or keyboard backlighting

[Tim McNamara]

I am running a Dell XPS 15. Updating to 20.04 means that the keyboard bindings for changing the brightness and keypad backlighting don't work. The icons appear on the screen, but the brightness does not change.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xorg 1:7.7+19ubuntu14
ProcVersionSignature: Ubuntu 5.4.0-12.15-generic 5.4.8
Uname: Linux 5.4.0-12-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu16
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Wed Feb 12 09:23:22 2020
DistUpgraded: 2020-02-08 14:25:17,407 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: focal
DistroVariant: ubuntu
DkmsStatus:
 virtualbox, 6.1.2, 5.3.0-29-generic, x86_64: installed
 virtualbox, 6.1.2, 5.4.0-12-generic, x86_64: installed
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation UHD Graphics 630 (Mobile) [8086:3e9b] (prog-if 00 [VGA controller])
   Subsystem: Dell UHD Graphics 630 (Mobile) [1028:087c]
   Subsystem: Dell GP107M [GeForce GTX 1050 Ti Mobile] [1028:087c]
InstallationDate: Installed on 2018-11-21 (447 days ago)
InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.3)
MachineType: Dell Inc. XPS 15 9570
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-12-generic root=UUID=78400725-c498-408a-af83-69891ddf09e4 ro quiet splash nouveau.modeset=0 acpi_osi=Linux vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to focal on 2020-02-08 (3 days ago)
dmi.bios.date: 11/08/2019
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.14.0
dmi.board.name: 0D0T05
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.14.0:bd11/08/2019:svnDellInc.:pnXPS159570:pvr:rvnDellInc.:rn0D0T05:rvrA00:cvnDellInc.:ct10:cvr:
dmi.product.family: XPS
dmi.product.name: XPS 15 9570
dmi.product.sku: 087C
dmi.sys.vendor: Dell Inc.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.100+git2002011830.5c8ff5~oibaf~d
version.libgl1-mesa-dri: libgl1-mesa-dri 20.1~git2002030730.a4e627~oibaf~d
version.libgl1-mesa-glx: libgl1-mesa-glx 20.1~git2002030730.a4e627~oibaf~d
version.xserver-xorg-core: xserver-xorg-core 2:1.20.7-2ubuntu1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20190815-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1

[Daniel van Vugt (vanvugt)]

First a small warning: You seem to be using the 'oibaf' graphics PPA which is not supported and is known to cause bugs. However I think it's unlikely that's relevant here.

Second, other people are already reporting that having the Nvidia driver installed has broken their brightness control. See bug 1861532 and bug 1857764.

Please try uninstalling the Nvidia driver, and try uninstalling that PPA.

[Daniel van Vugt (vanvugt)]

Also, have a look in /sys/class/backlight/... and see if you have any working entries that allow you to control the brightness by writing to them.

[Tim McNamara (tim-clicks)]

I've removed the NVIDIA drivers and configured Ubuntu to use Nouveau.

  sudo apt-get remove --purge '^nvidia-.*'
  sudo apt-get install ubuntu-desktop
  echo 'nouveau' | sudo tee -a /etc/modules

This hasn't fixed the situation. Altering the settings does not affect the actual screen brightness (or the keyboard backlight).

/sys/class/backlight/intel_backlight/actual_brightness doesn't change, although the indicators do.

[Daniel van Vugt (vanvugt)]

Please try reading and writing new values to:

  /sys/class/backlight/intel_backlight/brightness

instead of 'actual_brightness'. To find out the value corresponding to 100% brightness for your LCD look in the file 'max_brightness'.

[Tim McNamara (tim-clicks)]

After a restart, the keyboard backlight is now controllable via Fn+F10. Writing a new value to the brightness file doesn't appear to change anything though (am not sure what the API is.. legal values appear to be 0..256 exclusive)

[Daniel van Vugt (vanvugt)]

Legal values are 0 to whatever is in max_brightness

OK, the next step is to double check there exists no other

  /sys/class/backlight/*

directory. Just in case you have multiple backlight devices, which is not uncommon.

Regardless, I think we are at the stage where it can be said to be a kernel bug. Are you able to identify an older kernel version which doesn't have the bug? Or even if you boot 19.10 from USB?

[treb0r (treb0r)]

Similar problem here.

Dell XPS 9570
Ubuntu 20.04

Unable to change screen brightness at all, either using function keys or settings.

Keyboard backlight brightness works as expected.

[David (doylepd)]

Same problem here.

Found a mitigation that works:

https://github.com/TillmannBerg/Ubuntu-Dell-XPS-15-2019#screen-brightness-oled

[Daniel van Vugt (vanvugt)]

Someone experiencing this bug on a Dell 9570 please follow the steps in comment #8.

[Kai-Heng Feng (kaihengfeng)]

Please test latest drm-tip kernel:
https://kernel.ubuntu.com/~kernel-ppa/mainline/drm-tip/current/

[treb0r (treb0r)]

I upgraded to 5.4.0-18-generic and the problem is now fixed. Both screen backlight and keyboard backlight controls are now working as expected.

[Daniel van Vugt (vanvugt)]

Let's not confuse people, that's only fix-committed while it's in proposed.

[Mathew Robinson (mathew-robinson)]

This was fixed for me but now has started reoccurring after updating to the beta. Linux kernel:

Linux rocinante 5.4.0-1002-oem #4-Ubuntu SMP Wed Jan 15 10:44:42 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

[Daniel van Vugt (vanvugt)]

We should probably defer to the original reporter, Tim. If it's fixed for him then "Fix Released" and Mathew please open a new bug.

[Mathew Robinson (mathew-robinson)]

I have opened: https://bugs.launchpad.net/ubuntu/+source/linux-oem-5.4/+bug/1871330

Thanks!

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]