Touchpad spontaneously starts ignoring taps

[Valentin Nechayev]

Started as far as I see with kernel 5.4.0-90-generic. Previous one was -89 without observing the effect.
After system start, touchpad works as expected (single tap for left button, two fingers for right button, etc.)
At an arbitrary moment, tapping stops to be recognized.
`xev` shows just motions but not presses.
Physical buttons (at bottom edge of the touch field) continue working.
Pointer moving and two-finger scrolling continue working.
Just taps-as-button-presses stop.

I can cure it in a strange way: enter (KDE) System Settings -> Input Devices -> Touchpad and uncheck "Tap-to-click", after this "Apply" is not active; but when I check "Tap-to-click" on again, "Apply" gets active. Applying restores the functionality.

I'm unsure this belongs fully to the driver (at kernel) but this looks the best guess now.

I can do additional checks if detailedly specified what to run.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-90-generic 5.4.0-90.101
ProcVersionSignature: Ubuntu 5.4.0-90.101-generic 5.4.148
Uname: Linux 5.4.0-90-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.21
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: netch 1103 F.... pulseaudio
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Fri Nov 26 11:21:06 2021
InstallationDate: Installed on 2020-03-31 (604 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200329)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 002: ID 0408:a061 Quanta Computer, Inc. HD User Facing
 Bus 001 Device 003: ID 8087:0026 Intel Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-90-generic root=UUID=f0e11bcf-ab0e-4a7d-b264-b3cf33a88233 ro
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-90-generic N/A
 linux-backports-modules-5.4.0-90-generic N/A
 linux-firmware 1.187.20
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/07/2020
dmi.bios.vendor: Insyde Corp.
dmi.bios.version: V1.12
dmi.board.asset.tag: Type2 - Board Asset Tag
dmi.board.name: Doc_IL
dmi.board.vendor: IL
dmi.board.version: V1.12
dmi.chassis.type: 10
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnInsydeCorp.:bvrV1.12:bd09/07/2020:svnAcer:pn:pvrV1.12:rvnIL:rnDoc_IL:rvrV1.12:cvnChassisManufacturer:ct10:cvrChassisVersion:
dmi.product.family: ........................
dmi.product.sku: 0000000000000000
dmi.product.version: V1.12
dmi.sys.vendor: Acer

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.