** Description changed: Since linux 7.0.0-28.28 (resolute) the internal eDP panel of a ThinkPad T480 no longer comes back after the first suspend/resume (S3, "deep"). The external HDMI monitor resumes normally. Only a reboot restores the internal panel. 7.0.0-27 and earlier are fine. Hardware - ThinkPad T480 20L6S68T2W, BIOS N24ET81W (1.56), Intel Kaby Lake-R UHD Graphics 620 [8086:5917] rev 07, i915 - Internal panel: LG Display LP140WF6-SPB7 (EDID LGD 0x1313), 1920x1080 eDP, PWM backlight (intel_backlight) - Ubuntu 26.04 LTS, KDE Plasma 6.6.6 / KWin 6.6.6 Wayland, Secure Boot on (lockdown=integrity) - mem_sleep: s2idle [deep] (S3), no custom kernel parameters before the workaround Symptom after resume (all observed on 7.0.0-30, identical on -28/-29) - eDP-1: status=connected, enabled=enabled, dpms=On; KWin drives it at 1920x1080@60 (kscreen-doctor shows it enabled, brightness control "supported") - /sys/class/backlight/intel_backlight: brightness writes are accepted and read back (308 -> 1023 -> 308), bl_power=0 - Panel stays completely black with NO backlight glow even at brightness 1023; also no faint image with a flashlight - Toggling bl_power 1/0, kscreen-doctor output.eDP-1.disable/enable, and kscreen-doctor --dpms off/on do NOT bring the backlight back - Zero i915/drm errors in dmesg around suspend/resume - eDP has no i915_psr_status entry in debugfs (PSR not used on this panel) so PSR is not involved Regression window (from journalctl --list-boots, counting "PM: suspend exit" per boot) - 7.0.0-22: 29 and 60 suspends per boot, fine (June 2026) - 7.0.0-27: 13, 16, 5, 21 suspends per boot, fine (2 to 27 July 2026) - 7.0.0-28 (installed 28 July): every boot since then has 0 or 1 suspend followed by a reboot, because the panel never came back - 7.0.0-29 and 7.0.0-30: same as -28 The 7.0.0-28 changelog contains the backported series "Internal display black screen on Intel Lunar Lake with eDP panel" (LP: #2156312), including: - drm/i915/backlight: Remove try_vesa_interface - drm/i915/backlight: Take luminance_set into account for VESA backlight - drm/i915/backlight: Check luminance_set when disabling PWM via AUX VESA backlight - drm/i915/backlight: Short circuit intel_dp_aux_supports_hdr_backlight - drm/i915/backlight: Check if VESA backlight is possible - drm/i915/backlight: Fix VESA backlight possible check condition These change PWM vs DPCD/VESA AUX backlight selection, which matches the symptom (image path fine, PWM backlight not re-enabled on resume). Workaround (verified) - echo 'options i915 enable_dpcd_backlight=0' > /etc/modprobe.d/i915-resume.conf - update-initramfs -u -k all + echo 'options i915 enable_dpcd_backlight=0' > /etc/modprobe.d/i915-resume.conf + update-initramfs -u -k all With this option on 7.0.0-30 the internal panel comes back after suspend/resume. /sys/module/i915/parameters/enable_dpcd_backlight reads 0. Expected: the internal panel backlight is re-enabled on resume with the default enable_dpcd_backlight=-1, as it was up to 7.0.0-27. Happy to test a kernel with the series reverted or with a fix, or to provide drm.debug logs of a resume. Related to bug #2156312 (the backported series that introduced the change) ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-30-generic 7.0.0-30.30 ProcVersionSignature: Ubuntu 7.0.0-30.30-generic 7.0.12 Uname: Linux 7.0.0-30-generic x86_64 ApportVersion: 2.34.1-0ubuntu0.1 Architecture: amd64 AudioDevicesInUse: - USER PID ACCESS COMMAND - /dev/snd/controlC0: zak 2240 F.... wireplumber - /dev/snd/seq: zak 2211 F.... pipewire + USER PID ACCESS COMMAND + /dev/snd/controlC0: user 2240 F.... wireplumber + /dev/snd/seq: user 2211 F.... pipewire CasperMD5CheckResult: unknown CurrentDesktop: KDE Date: Fri Sep 4 02:52:45 2026 InstallationDate: Installed on 2026-02-21 (194 days ago) InstallationMedia: Kubuntu 25.10 "Questing Quokka" - Release amd64 (20251007) MachineType: LENOVO 20L6S68T2W ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-30-generic root=UUID=4d75fb6a-ab95-47a9-a69a-43be15458017 ro quiet rd.luks.uuid=47b20a4b-446e-40c3-9513-2d48d619f414 splash PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon. SourcePackage: linux UpgradeStatus: Upgraded to resolute on 2026-05-22 (104 days ago) dmi.bios.date: 09/06/2025 dmi.bios.release: 1.56 dmi.bios.vendor: LENOVO dmi.bios.version: N24ET81W (1.56 ) dmi.board.asset.tag: Not Available dmi.board.name: 20L6S68T2W dmi.board.vendor: LENOVO dmi.board.version: SDK0J40697 WIN dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: None dmi.ec.firmware.release: 1.22 dmi.modalias: dmi:bvnLENOVO:bvrN24ET81W(1.56):bd09/06/2025:br1.56:efr1.22:svnLENOVO:pn20L6S68T2W:pvrThinkPadT480:rvnLENOVO:rn20L6S68T2W:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20L6_BU_Think_FM_ThinkPadT480:pfaThinkPadT480: dmi.product.family: ThinkPad T480 dmi.product.name: 20L6S68T2W dmi.product.sku: LENOVO_MT_20L6_BU_Think_FM_ThinkPad T480 dmi.product.version: ThinkPad T480 dmi.sys.vendor: LENOVO
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2166429 Title: [regression 7.0.0-28] ThinkPad T480 (UHD 620): internal eDP backlight stays off after suspend/resume, i915.enable_dpcd_backlight=0 fixes it To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2166429/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
