UPDATE - WORKAROUND FOUND Machine: Dell Latitude 7390 GPU: Intel UHD Graphics 620 (Kabylake, device ID 5917) OS: Linux Mint 22.3 (Ubuntu 24.04 base) Kernel: 7.0.0-28-generic
Adding kernel parameter i915.enable_dpcd_backlight=0 to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub fixes the issue. Before fix: - max_brightness: 1023 - Screen extremely dark even at 100% brightness - Below 50% completely black - Unusable without High Contrast accessibility mode After adding i915.enable_dpcd_backlight=0: - max_brightness: 7500 (restored to correct scale) - All brightness levels working correctly - Minimum brightness still visible - Screen fully usable Root cause appears to be kernel 7.0 defaulting to DPCD backlight control for eDP panels, which is not supported correctly on this hardware. Forcing PWM backlight control via enable_dpcd_backlight=0 restores correct behavior. To apply workaround: sudo nano /etc/default/grub GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_dpcd_backlight=0" sudo update-grub sudo reboot -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2161148 Title: [SRU] intel_backlight (i915/eDP AUX-DPCD) stops responding to live brightness writes in 7.0.0-28-generic (works in 6.17.0-40-generic) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161148/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
