Public bug reported:
Hardware:
- Dell Latitude 7490
- Intel UHD Graphics 620 (Kaby Lake)
- Internal display: AUO B140HAK
- Ubuntu 24.04.3 LTS
Problem:
After upgrading from Linux kernel 6.17.0-35-generic to 7.0.0-28-generic,
the internal laptop display becomes significantly dimmer.
The brightness reduction is immediately visible when the i915 driver
takes control during boot.
Observed behaviour:
1. BIOS splash screen:
Bright.
2. Dell diagnostics (Display test using D key):
Bright.
3. Windows:
Brightness is normal.
4. Ubuntu with kernel 6.17.0-35:
Brightness is normal.
5. Ubuntu with kernel 7.0.0-28:
Display becomes noticeably dimmer immediately after the kernel initializes
the graphics driver.
The brightness remains low from the login screen onwards.
brightnessctl reports 100% brightness in both kernels.
Kernel 6.17:
max_brightness = 7500
actual_brightness = 7500
Kernel 7.0:
max_brightness = 1023
actual_brightness = 1023
Although different brightness scales do not necessarily indicate a
problem, the reduction coincides with a very obvious visual decrease in
luminance.
Additional observations:
- Only one backlight device exists:
/sys/class/backlight/intel_backlight
- Backlight type:
raw
- No relevant i915 or backlight errors appear in dmesg.
The issue is fully reproducible simply by booting either kernel.
This strongly suggests a regression in the i915 backlight handling
between kernels 6.17 and 7.0 for this hardware.
Additional information available:
- EDID
- i915_display_info
- i915_power_domain_info
- display_info comparison between kernels
- power_domain comparison between kernels
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28~24.04.1
ProcVersionSignature: Ubuntu 7.0.0-28.28~24.04.1-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Wed Aug 5 11:33:30 2026
InstallationDate: Installed on 2025-12-03 (245 days ago)
InstallationMedia: Ubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
SourcePackage: linux-signed-hwe-7.0
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: linux-signed-hwe-7.0 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
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https://bugs.launchpad.net/bugs/2162894
Title:
Regression: Significant reduction of internal display brightness on
Dell Latitude 7490 after upgrading from kernel 6.17 to 7.0
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