Public bug reported:
After upgrading to the 7.0 HWE kernel series, my ThinkPad X240 (Haswell-ULT,
i915)
no longer restores the display after resuming from deep sleep (S3).
The system itself resumes correctly: "PM: suspend exit" is logged, tasks
restart,
Wi-Fi reconnects, Bluetooth comes back and GDM starts accepting input. Only the
panel stays black — both the internal display and the backlight. The only way
out
is a hard power-off.
This is a regression: kernel 6.17.0-35-generic is completely unaffected on the
same
machine, with dozens of suspend/resume cycles and no warnings at all.
Two kernels of the 7.0 series were tested, both fail identically:
7.0.0-28.28~24.04.1 tested 2026-07-20 FAIL
7.0.0-29.29~24.04.2 tested 2026-08-18 FAIL
6.17.0-35.35~24.04.1 in daily use OK
On every failing resume the kernel logs the same warning pair, at the same
source
lines, with the same call path:
i915 0000:00:02.0: [drm] CPU PWM1 enabled
WARNING: drivers/gpu/drm/i915/display/intel_display_power.c:1225
at assert_can_disable_lcpll+0x70e/0x880 [i915], CPU#3:
kworker/u16:1/47
Call Trace:
hsw_disable_lcpll.constprop.0+0x18/0x470 [i915]
hsw_enable_pc8+0x44/0xc0 [i915]
intel_display_power_suspend_late+0x6a/0xf0 [i915]
i915_drm_suspend_late+0x81/0x110 [i915]
i915_pm_suspend_late+0x1d/0x40 [i915]
pm_generic_suspend_late+0x2b/0x40
pci_pm_suspend_late+0x33/0x50
dpm_run_callback+0x54/0x1d0
i915 0000:00:02.0: [drm] PCH PWM1 enabled
WARNING: drivers/gpu/drm/i915/display/intel_display_power.c:1232
at assert_can_disable_lcpll+0x770/0x880 [i915]
The driver disables LCPLL while entering PC8 with the backlight PWM still
enabled,
and the display state is not restored correctly afterwards.
STEPS TO REPRODUCE
1. Boot 7.0.0-29-generic on a Haswell-ULT laptop.
2. Close the lid, wait ~30 seconds, open it.
3. The machine resumes but the panel stays black.
4. dmesg (previous boot) shows the WARNING above.
EXPECTED
The display resumes, as it does on 6.17.0-35-generic.
WHAT I ALREADY RULED OUT
- Sleep mode is "deep" (S3), which is correct for this machine;
/sys/power/mem_sleep
reads "s2idle [deep]". Switching away from S3 is not an acceptable workaround
here,
the machine must keep full power saving.
- A systemd unit poking the backlight brightness after resume does not help.
- The warning is emitted during suspend-late, not during resume; the log
timestamps
only appear at resume time because the kernel ring buffer is flushed then.
SYSTEM
Ubuntu 24.04.4 LTS
Machine: LENOVO 20AL008YUS, ThinkPad X240
BIOS: GIET99WW (2.49), 2020-03-17
GPU: Intel Haswell-ULT Integrated Graphics [8086:0a16] rev 0b,
subsystem Lenovo ThinkPad X240 [17aa:2214], driver i915
Package: linux-image-7.0.0-29-generic 7.0.0-29.29~24.04.2
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.17.0-35-generic 6.17.0-35.35~24.04.1
ProcVersionSignature: Ubuntu 6.17.0-35.35~24.04.1-generic 6.17.13
Uname: Linux 6.17.0-35-generic x86_64
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: ppasam 2661 F.... wireplumber
/dev/snd/controlC0: ppasam 2661 F.... wireplumber
/dev/snd/seq: ppasam 2655 F.... pipewire
CRDA: N/A
CasperMD5CheckMismatches:
./pool/restricted/n/nvidia-graphics-drivers-535/libnvidia-gl-535_535.183.01-0ubuntu0.24.04.1_amd64.deb
./pool/restricted/n/nvidia-graphics-drivers-550/nvidia-kernel-source-550_550.120-0ubuntu0.24.04.1_amd64.deb
./pool/restricted/n/nvidia-graphics-drivers-550/nvidia-firmware-550-550.120_550.120-0ubuntu0.24.04.1_amd64.deb
./pool/restricted/n/nvidia-graphics-drivers-550/libnvidia-gl-550_550.120-0ubuntu0.24.04.1_amd64.deb
./pool/main/l/linux-oem-6.8/linux-modules-6.8.0-1020-oem_6.8.0-1020.20_amd64.deb
./pool/main/l/linux-firmware/linux-firmware_20240318.git3b128b60-0ubuntu2.9_amd64.deb
./pool/main/l/linux-hwe-6.11/linux-hwe-6.11-headers-6.11.0-17_6.11.0-17.17~24.04.2_all.deb
./casper/minimal.standard.ru.squashfs ./casper/minimal.standard.live.squashfs
./casper/initrd
CasperMD5CheckResult: fail
CurrentDesktop: ubuntu:GNOME
Date: Tue Aug 18 10:47:53 2026
InstallationDate: Installed on 2025-11-12 (279 days ago)
InstallationMedia: Ubuntu 24.04.2 LTS "Noble Numbat" - Release amd64 (20250215)
MachineType: LENOVO 20AL008YUS
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-6.17.0-35-generic
root=UUID=0fb347d2-5d25-44f9-bac1-1b22828af02a ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-6.17.0-35-generic N/A
linux-backports-modules-6.17.0-35-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.29
SourcePackage: linux-hwe-6.17
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/17/2020
dmi.bios.release: 2.49
dmi.bios.vendor: LENOVO
dmi.bios.version: GIET99WW (2.49 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20AL008YUS
dmi.board.vendor: LENOVO
dmi.board.version: 0B98401 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.ec.firmware.release: 1.17
dmi.modalias:
dmi:bvnLENOVO:bvrGIET99WW(2.49):bd03/17/2020:br2.49:efr1.17:svnLENOVO:pn20AL008YUS:pvrThinkPadX240:rvnLENOVO:rn20AL008YUS:rvr0B98401WIN:cvnLENOVO:ct10:cvrNotAvailable:skuLENOVO_MT_20AL_BU_Think_FM_ThinkPadX240:
dmi.product.family: ThinkPad X240
dmi.product.name: 20AL008YUS
dmi.product.sku: LENOVO_MT_20AL_BU_Think_FM_ThinkPad X240
dmi.product.version: ThinkPad X240
dmi.sys.vendor: LENOVO
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
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https://bugs.launchpad.net/bugs/2163734
Title:
i915/Haswell: black screen after resume from S3 on 7.0 kernels —
assert_can_disable_lcpll WARNING (regression vs 6.17)
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