apport information ** Tags added: apport-collected resolute wayland-session
** Description changed: After upgrading to Ubuntu 26.04 (kernel 7.0.0-generic), screen brightness can no longer be changed on a Dell XPS 13 Plus (9320) developer edition with the UHD+ 3840x2400 LCD panel (Alder Lake-P / Raptor Lake-P graphics, device ID a7a0, i915 driver). The GNOME brightness OSD appears and the slider moves, and the sysfs interface accepts values, but the panel brightness does not actually change. This is a regression: booting the previously installed 6.17.0-35-generic kernel on the same system, brightness control works normally. Kernels 7.0.0-28-generic and 7.0.0-29-generic are both affected. ## Symptoms / evidence - /sys/class/backlight contains only intel_backlight (no acpi_video0). - Writes to /sys/class/backlight/intel_backlight/brightness are accepted; both `brightness` and `actual_brightness` track the written value (max_brightness = 1023), but the panel does not change. - brightnessctl and the GNOME slider show the same behavior: values change, panel does not. - dmesg contains no backlight/PWM/panel errors at all. The only i915 anomaly is: `i915 0000:00:02.0: [drm] Selective fetch area calculation failed in pipe A` - Brightness set in the firmware setup (BIOS) works and persists into the 7.0.0 session, so the backlight hardware itself is functional; the OS just cannot drive it. - Brightness set while booted into 6.17.0-35 also persists into a subsequent 7.0.0 boot. ## Ruled out - i915.enable_psr=0: verified active via /sys/kernel/debug/dri/1/eDP-1/i915_psr_status (PSR mode: disabled). No effect on the bug. (With defaults, PSR2 is enabled and the panel sits in DEEP_SLEEP.) - i915.enable_dpcd_backlight=3: verified active via /sys/module/i915/parameters/enable_dpcd_backlight. No effect; max_brightness stayed at 1023, so the driver remained on the PWM path. This suggests the panel is PWM-dimmed and the regression is in the PWM backlight path. - Firmware is current (fwupd reports no pending updates). - Kernel driver in use is i915 (not xe). ## Regression window - Works: 6.17.0-35-generic (Ubuntu 25.10 kernel) - Broken: 7.0.0-28-generic, 7.0.0-29-generic (Ubuntu 26.04) ## Hardware - Dell XPS 13 Plus 9320, UHD+ 3840x2400 LCD (eDP-1), touch - Intel Alder Lake-P/Raptor Lake-P integrated graphics, device ID a7a0, display version 13.00 stepping E0 - Wayland session (GNOME), Secure Boot enabled (kernel lockdown: integrity) ## Workaround - Boot 6.17.0-35 (or enter BIOS setup) to set a brightness level, which - then persists into 7.0.0 sessions; brightness is otherwise fixed at that - level. + Boot 6.17.0-35 (or enter BIOS setup) to set a brightness level, which then persists into 7.0.0 sessions; brightness is otherwise fixed at that level. + --- + ProblemType: Bug + ApportVersion: 2.34.1-0ubuntu0.1 + Architecture: amd64 + AudioDevicesInUse: + USER PID ACCESS COMMAND + /dev/snd/controlC0: saalfeld 5142 F.... pipewire + saalfeld 5160 F.... wireplumber + /dev/snd/seq: saalfeld 5142 F.... pipewire + CasperMD5CheckResult: pass + CurrentDesktop: ubuntu:GNOME + DistributionChannelDescriptor: + # This is the distribution channel descriptor for the OEM CDs + # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor + canonical-oem-somerville-jammy-amd64-20220504-33 + DistroRelease: Ubuntu 26.04 + InstallationDate: Installed on 2023-08-25 (1087 days ago) + InstallationMedia: Ubuntu 22.04 LTS "Jammy Jellyfish" - somerville-jammy-amd64-20220504-33 + MachineType: Dell Inc. XPS 9320 + Package: linux (not installed) + ProcEnviron: + LANG=en_US.UTF-8 + PATH=(custom, no user) + SHELL=/bin/bash + TERM=xterm-256color + XDG_RUNTIME_DIR=<set> + ProcFB: 0 i915drmfb + ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-29-generic root=UUID=e3cab906-301b-4c1d-b143-48e1391c0a45 ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M + ProcVersionSignature: Ubuntu 7.0.0-29.29-generic 7.0.12 + PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon. + Tags: resolute wayland-session + Uname: Linux 7.0.0-29-generic x86_64 + UpgradeStatus: Upgraded to resolute on 2026-06-10 (67 days ago) + UserGroups: adm cdrom dip docker lpadmin nordvpn ollama plugdev sambashare sudo video + _MarkForUpload: True + dmi.bios.date: 05/28/2026 + dmi.bios.release: 2.31 + dmi.bios.vendor: Dell Inc. + dmi.bios.version: 2.31.0 + dmi.board.name: 0CR6NC + dmi.board.vendor: Dell Inc. + dmi.board.version: A00 + dmi.chassis.type: 10 + dmi.chassis.vendor: Dell Inc. + dmi.ec.firmware.release: 1.17 + dmi.modalias: dmi:bvnDellInc.:bvr2.31.0:bd05/28/2026:br2.31:efr1.17:svnDellInc.:pnXPS9320:pvr:rvnDellInc.:rn0CR6NC:rvrA00:cvnDellInc.:ct10:cvr:sku0C10:pfaXPS: + dmi.product.family: XPS + dmi.product.name: XPS 9320 + dmi.product.sku: 0C10 + dmi.sys.vendor: Dell Inc. ** Attachment added: "AlsaInfo.txt" https://bugs.launchpad.net/bugs/2163601/+attachment/5992613/+files/AlsaInfo.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2163601 Title: Regression: i915 backlight control broken on Dell XPS 13 Plus (9320, UHD+ panel) with kernel 7.0.0, worked on 6.17.0 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2163601/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
