Public bug reported:
System information
------------------
OS: Ubuntu 26.04 LTS
Kernel: 7.0.0-28-generic
ModemManager: 1.25.95
NetworkManager: 1.54.3
Laptop: HP EliteBook 840 14-inch G11
Modem:
MediaTek T700 5G Modem / Intel 5G Solution 5000
PCI ID: 14c3:4d75
Subsystem: 103c:8914
Driver: mtk_t7xx
Interface: MBIM
NetworkManager connection profile: 019-Free
Problem
-------
The cellular modem is sometimes missing after restoring the system from
hibernation.
Hibernation and system restore complete successfully, but ModemManager
sometimes probes the PCIe modem before all WWAN ports and the associated
network interface have finished appearing.
The problem appears to be intermittent.
Steps to reproduce
------------------
1. Boot Ubuntu and connect using the cellular connection.
2. Verify that the modem is visible with:
mmcli -L
nmcli device status
3. Hibernate the system:
systemctl hibernate
4. Power the computer on and restore the hibernation image.
5. Check the modem again:
mmcli -L
nmcli device status
Expected result
---------------
The modem should be recreated by ModemManager and the existing cellular
connection should reconnect automatically.
Actual result
-------------
On the failed resume, the kernel first disconnects and then reattaches the
WWAN ports:
wwan wwan0: port wwan0at0 disconnected
wwan wwan0: port wwan0mbim0 disconnected
wwan wwan0: port wwan0at0 attached
wwan wwan0: port wwan0mbim0 attached
ModemManager then reports:
couldn't check support for device
'/sys/devices/pci0000:00/0000:00:1c.0/0000:56:00.0':
not supported by any plugin
additional port wwan0mbim0 in device
'/sys/devices/pci0000:00/0000:00:1c.0/0000:56:00.0'
added after device probing has already finished
creating modem with plugin 'mtk' and '2' ports
teardown not called before dispose
couldn't create modem for device
'/sys/devices/pci0000:00/0000:00:1c.0/0000:56:00.0':
Failed to find a net port in the MBIM modem
After this failure, mmcli does not list the modem. A full reboot restores
the modem and the cellular connection.
Workaround
----------
I installed a delayed post-hibernate recovery hook.
The hook waits until:
/dev/wwan*mbim*
/sys/class/net/wwan*
are available. It then checks mmcli -L and restarts ModemManager only if
no modem is detected.
A subsequent hibernate/resume cycle completed successfully, but the issue
did not reproduce during that cycle, so the restart recovery path has not
yet been exercised after another failure.
Additional notes
----------------
The kernel successfully completed S4 hibernation and restored the system.
I did not see mtk_t7xx suspend errors such as "SAP suspend error" or
"failed to suspend".
This looks like a race between the delayed creation of the WWAN/MBIM/net
ports and ModemManager finishing device probing.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: modemmanager 1.25.95-1ubuntu1
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Thu Jul 30 22:13:43 2026
InstallationDate: Installed on 2026-07-25 (5 days ago)
InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1)
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
RebootRequiredPkgs: Error: path contained symlinks.
SourcePackage: modemmanager
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.dbus-1.system.d.org.freedesktop.ModemManager1.conf:
[deleted]
** Affects: modemmanager (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
** Attachment added: "Logs showing intermittent WWAN port enumeration failure
after hibernate resume"
https://bugs.launchpad.net/bugs/2162379/+attachment/5988123/+files/wwan-hibernate-failure-2026-07-30.txt
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https://bugs.launchpad.net/bugs/2162379
Title:
Intermittent MediaTek T700 modem loss after hibernate resume due to
late WWAN port enumeration
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