Recently, on this Dell Latitude 7380, running Ubuntu 24.04.4 LTS with Wayland, the kernel updated from v. 6.17.0-40-generic to 7.0.0-28-generic. After rebooting the display became extremely dark, starting immediately after the selection of OS was made in grub. It was barely readable in a dimly lit room, and it also appeared to flicker slightly.
Rebooting and selecting kernel 6.17.0-40 from grub worked normally, with fully controllable brightness. Retesting both kernels gave consistent results. For now, I've changed the grub selection order so that 6.17.0-40 is the first, i.e., default entry. That kernel and its header also have been set on hold. However, I'd like to know what causes the issue, and if there is a workaround, or newer kernel in the pipeline that could be tested to see if the issue has been resolved.
The results of uname -a are as follows for the new and old kernels, respectively:
Linux <PC_NAME> 7.0.0-28-generic #28~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Jul 1 15:50:57 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
Linux <PC_NAME> 6.17.0-40-generic #40~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Tue Jun 23 16:48:12 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
Here are relevant parts of a system report:
Hardware Model: Dell Inc. Latitude 7380
Memory: 16.0 GiB
Processor: Intel® Core™ i7-6600U × 4
Graphics: Intel® HD Graphics 520 (SKL GT2)
Disk Capacity: 512.1 GB
Firmware Version: 1.38.0
OS Name: Ubuntu 24.04.4 LTS
GNOME Version: 46
Windowing System: Wayland
Values /sys/class/backlight/intel_backlight/:
Kernel: 6.17 7.0
max_brightness: 7500 1023
actual_brightness: 2136 1023
brightness: 2136 1023
bi_power: 0 0
scale: unknown unknown
type: raw raw
uevent: [null] [null]
Has kernel 7.0.0-28-generic dropped support for hardware in this older Dell?
Is there a conflict with Wayland windowing system?
Is there a driver needed?
Any help would be appreciated.