Public bug reported:

[Summary]
After upgrading from linux-image-6.8.0-117-lowlatency to 6.8.0-134-lowlatency
(installed 2026-07-05), the left built-in speaker produces a clicking/popping
sound approximately once per second during audio playback. When playback
stops, a burst of ~15 additional clicks occurs over several seconds, then
silence. Booting back into 6.8.0-117-lowlatency fully resolves the issue,
so this is a kernel regression between 6.8.0-117 and 6.8.0-134.

[Hardware]
- Laptop: DEXP Atlas M15-I5W303 (Hena M15), BIOS EM_IDL819_S_SUB53_V1.0.1
- CPU: 12th Gen Intel Core i5-1235U (Alder Lake-U)
- Audio: Intel PCH HDA (PCI 8086:51c8 at 0000:00:1f.3), codec Realtek ALC269VC
- Driver in use: legacy snd_hda_intel (SOF modules are loaded but the device
  is claimed by snd_hda_intel; card shows as "HDA Intel PCH")
- Codec pin config: line_outs=2 (0x14/0x1b) type:speaker, hp_outs=1 (0x15)

[Steps to reproduce]
1. Boot kernel 6.8.0-134-lowlatency on Ubuntu Studio 24.04.
2. Play any audio through the built-in speakers.
3. Observe a click from the LEFT speaker roughly every second.
4. Stop playback: observe ~15 more clicks over the next several seconds,
   then the clicking stops.

[Expected behavior]
Clean playback with no clicking, as on 6.8.0-117-lowlatency.

[Key observations]
- Only the LEFT speaker clicks; the right speaker is unaffected.
- Headphones (both 3.5mm jack and USB) are completely clean.
- The left speaker keeps clicking even WHILE headphones are plugged in,
  i.e. the clicks are not part of the audio stream — this looks like the
  codec/amp power state of one speaker pin being toggled.
- The "~15 clicks after playback stops" pattern resembles a staged
  widget/amp power-down sequence.
- Not related to runtime PM settings: the issue persists with
  snd_hda_intel power_save=0, power_save_controller=N, and with runtime PM
  forced to "on" for both the PCI device (00:1f.3) and all devices on the
  hdaudio bus.
- Not related to CPU C-states: persists with cpupower idle-set -D 2.
- No related messages appear in dmesg synchronized with the clicks.

[Regression details]
- Good: linux-image-6.8.0-117-lowlatency — no clicks at all
- Bad:  linux-image-6.8.0-134-lowlatency — clicks as described
- The upgrade that introduced the issue was installed on 2026-07-05.

[Workaround]
Booting the previous kernel 6.8.0-117-lowlatency (held via apt-mark hold).

I can test intermediate kernel versions or patches to help bisect if
needed.

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.8.0-134-lowlatency 6.8.0-134.134.1
ProcVersionSignature: Ubuntu 6.8.0-134.134.1-lowlatency 6.8.12
Uname: Linux 6.8.0-134-lowlatency x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
AudioDevicesInUse:
 USER        PID ACCESS COMMAND
 /dev/snd/controlC0:  victor     3864 F.... wireplumber
 /dev/snd/controlC1:  victor     3864 F.... wireplumber
 /dev/snd/seq:        victor     3858 F.... pipewire
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: KDE
Date: Mon Jul  6 20:23:30 2026
InstallationDate: Installed on 2025-02-05 (516 days ago)
InstallationMedia: Ubuntu-Studio 24.04.1 LTS "Noble Numbat" - Release amd64 
(20240827)
Lsusb:
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 003: ID 0495:804a ESS Technology, Inc. Beam 3Plus
 Bus 001 Device 004: ID 1c4f:0048 SiGma Micro Usb Mouse
 Bus 001 Device 005: ID 13d3:3503 IMC Networks 
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
MachineType: DEXP Atlas M15-I5W303
ProcEnviron:
 LANG=ru_RU.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.8.0-134-lowlatency 
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash threadirqs vt.handoff=7
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No 
PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-6.8.0-134-lowlatency N/A
 linux-backports-modules-6.8.0-134-lowlatency  N/A
 linux-firmware                                20240318.git3b128b60-0ubuntu2.27
SourcePackage: linux-lowlatency
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/13/2023
dmi.bios.release: 5.25
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: EM_IDL819_S_SUB53_V1.0.1
dmi.board.asset.tag: Default string
dmi.board.name: Hena M15
dmi.board.vendor: Default string
dmi.board.version: Default string
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 10
dmi.chassis.vendor: Default string
dmi.chassis.version: Default string
dmi.ec.firmware.release: 0.2
dmi.modalias: 
dmi:bvnAmericanMegatrendsInternational,LLC.:bvrEM_IDL819_S_SUB53_V1.0.1:bd11/13/2023:br5.25:efr0.2:svnDEXP:pnAtlasM15-I5W303:pvrDefaultstring:rvnDefaultstring:rnHenaM15:rvrDefaultstring:cvnDefaultstring:ct10:cvrDefaultstring:sku5098373:
dmi.product.family: Atlas
dmi.product.name: Atlas M15-I5W303
dmi.product.sku: 5098373
dmi.product.version: Default string
dmi.sys.vendor: DEXP

** Affects: linux-lowlatency (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug noble

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https://bugs.launchpad.net/bugs/2159649

Title:
  Periodic clicking/popping from left speaker on kernel
  6.8.0-134-lowlatency (regression from 6.8.0-117) — DEXP Atlas M15,
  ALC269VC

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