Public bug reported:
Hardware: Lenovo ThinkPad X1 Carbon Gen 13 (21NS004UGE), Lunar Lake
BIOS: [dmidecode output]; fwupd reports system firmware as latest
OS: Ubuntu 26.04 LTS, kernel 7.0.0-38-generic
Modem: Quectel RM520N-GL, PCI 1eac:1007 (subsystem 1eac:100b), driver
mhi-pci-generic
ModemManager version: [mmcli --version]
Not listed in fwupd.
Problem:
The modem intermittently disappears from ModemManager. The kernel side stays
intact:
the device is bound to mhi-pci-generic, mhi_wwan_ctrl/mhi_wwan_mbim are loaded
and
/sys/class/wwan lists wwan0, wwan0at0, wwan0mbim0, wwan0qcdm0. mmcli -L reports
"No modems were found". rfkill shows no soft or hard block.
Timeline (single occurrences, not systematically reproduced):
- Sep 30: modem repeatedly goes unknown -> disabled (1013 transitions in one
boot);
at times "Cannot power-up: software radio switch is OFF".
- Oct 10-11: ModemManager logs MBIM transaction timeouts every ~30 s for ~25
hours.
Restarting ModemManager resolved it; the modem was then detected, registered
and connected.
- Oct 14: after a suspend/resume cycle (resume 13:37) ModemManager logs
"task 2022: port context already scheduled"; mmcli -L is empty afterwards.
A ModemManager restart on Oct 12 did not prevent the recurrence.
Result of direct MBIM query (mbimcli --query-device-caps): [fill in:
response or timeout]
Workaround: restarting ModemManager (not always sufficient) or complete Reboot
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-38-generic 7.0.0-38.38
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: mauricefink 5237 F.... wireplumber
/dev/snd/controlC0: mauricefink 5230 F.... pipewire
mauricefink 5237 F.... wireplumber
/dev/snd/seq: mauricefink 5230 F.... pipewire
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Thu Oct 15 10:51:09 2026
InstallationDate: Installed on 2026-09-28 (17 days ago)
InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1)
IwDevWlp0s20f3Link: Not connected.
MachineType: LENOVO 21NS004UGE
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 xedrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-38-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/12/2026
dmi.bios.release: 1.48
dmi.bios.vendor: LENOVO
dmi.bios.version: N4BET78W (1.48 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21NS004UGE
dmi.board.vendor: LENOVO
dmi.board.version: SDK0T76576 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.41
dmi.modalias:
dmi:bvnLENOVO:bvrN4BET78W(1.48):bd08/12/2026:br1.48:efr1.41:svnLENOVO:pn21NS004UGE:pvrThinkPadX1CarbonGen13:rvnLENOVO:rn21NS004UGE:rvrSDK0T76576WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21NS_BU_Think_FM_ThinkPadX1CarbonGen13:pfaThinkPadX1CarbonGen13:
dmi.product.family: ThinkPad X1 Carbon Gen 13
dmi.product.name: 21NS004UGE
dmi.product.sku: LENOVO_MT_21NS_BU_Think_FM_ThinkPad X1 Carbon Gen 13
dmi.product.version: ThinkPad X1 Carbon Gen 13
dmi.sys.vendor: LENOVO
** Affects: ubuntu
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2170954
Title:
Quectel RM520N-GL (1eac:1007) on ThinkPad X1 Carbon Gen 13: modem not
detected by ModemManager, recurring MBIM timeouts
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