QUECTEL 4G SIM, Invalid Transition Error on ThinkPad X1 Carbon Gen 12 with Ubuntu 24.04

[Benjamin AIMARD]

Logs :

```
2024-04-11T10:56:08.865232+02:00 0001 ModemManager[1212]: <msg> [modem0] simple connect started...
2024-04-11T10:56:08.865289+02:00 0001 ModemManager[1212]: <msg> [modem0] simple connect state (3/10): enable
2024-04-11T10:56:08.865309+02:00 0001 ModemManager[1212]: <msg> [modem0] state changed (disabled -> enabling)
2024-04-11T10:56:08.883819+02:00 0001 ModemManager[1212]: <msg> [modem0] simple connect started...
2024-04-11T10:56:08.883857+02:00 0001 ModemManager[1212]: <msg> [modem0] simple connect state (4/10): wait to get fully enabled
2024-04-11T10:56:10.785939+02:00 0001 ModemManager[1212]: <wrn> [modem0] Busy
2024-04-11T10:56:10.789923+02:00 0001 ModemManager[1212]: <wrn> [modem0] Busy
2024-04-11T10:56:10.789962+02:00 0001 ModemManager[1212]: <wrn> [modem0] couldn't enable interface: 'Invalid transition'
2024-04-11T10:56:10.845974+02:00 0001 ModemManager[1212]: <wrn> [modem0] failed enabling modem: Invalid transition
2024-04-11T10:56:10.846047+02:00 0001 ModemManager[1212]: <msg> [modem0] state changed (enabling -> disabled)
2024-04-11T10:56:10.846078+02:00 0001 ModemManager[1212]: <wrn> [modem0] failed waiting for enabled state: disabled
2024-04-11T10:56:10.846747+02:00 0001 NetworkManager[1172]: <info> [1712825770.8464] device (wwan0mbim0): state change: prepare -> disconnected (reason 'user-requested', sys-iface-state: 'managed')
2024-04-11T10:56:10.847007+02:00 0001 NetworkManager[1172]: <info> [1712825770.8469] policy: auto-activating connection 'Orange Orange Internet 1' (cddfb4fd-cbc0-4655-b4ad-5db26d9751ee)
2024-04-11T10:56:10.847323+02:00 0001 NetworkManager[1172]: <info> [1712825770.8472] device (wwan0mbim0): Activation: starting connection 'Orange Orange Internet 1' (cddfb4fd-cbc0-4655-b4ad-5db26d9751ee)
2024-04-11T10:56:10.847374+02:00 0001 NetworkManager[1172]: <info> [1712825770.8473] device (wwan0mbim0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
```

Description:
I am experiencing a problem with ModemManager on my ThinkPad X1 Carbon Gen 12 running Ubuntu 24.04. The issue occurs when attempting to establish a mobile broadband connection. The modem enters an enable sequence but fails with an "Invalid transition" error, leading to a failure in enabling the modem and thus preventing the connection.

Steps to Reproduce:

Start or restart Ubuntu 24.04 on a ThinkPad X1 Carbon Gen 12.
Attempt to connect to a mobile broadband network using the default Network Manager GUI.
Observe the failure in the connection process "/var/log/syslog".

Expected Result:
The modem successfully transitions through its enable sequence, allowing the mobile broadband connection to be established without errors.

Actual Result:
The modem fails to enable, logging an "Invalid transition" error. This results in the modem being stuck in a disabled state, and the connection process is halted. The specific error messages from the ModemManager log are as follows:

ModemManager initiates the simple connect process, moving through states to enable the modem.
The modem state changes from disabled to enabling.
Shortly after, warnings of "Busy" are logged, followed by "couldn't enable interface: 'Invalid transition'" and "failed enabling modem: Invalid transition."
Eventually, the modem transitions back to the disabled state, and NetworkManager logs indicate a fallback to a disconnected state due to a 'user-requested' action.
System Information:

Device: ThinkPad X1 Carbon Gen 12
lsb_release -rd
No LSB modules are available.
Description: Ubuntu Noble Numbat (development branch)
Release: 24.04

Solution for the community :) :

After further investigation and testing, I have found a workaround that successfully resolves the issue with ModemManager not being able to enable the modem, which was preventing the establishment of mobile broadband connections.

Solution Description:
The solution involves two main steps:

- Creating Symbolic Links for FCC Unlock Settings: This step ensures that ModemManager has the necessary permissions and configurations to manage the modem's FCC lock state.

- Directly Setting the Radio State to 'On' Using mbimcli: This command directly interacts with the modem to enable its radio, bypassing the limitations encountered with the Network Manager command-line interface (CLI) or graphical user interface (GUI).

Steps to Apply the Solution:

Create symbolic links for FCC unlock settings by running the following command in the terminal:

bash

sudo ln -sft /etc/ModemManager/fcc-unlock.d /usr/share/ModemManager/fcc-unlock.available.d/*

Enable the modem's radio state to 'on' using mbimcli by executing:

bash

sudo mbimcli -p -d /dev/wwan0mbim0 --quectel-set-radio-state=on

Note: These actions were not achievable through the Network Manager CLI interface or its GUI, indicating a limitation in the existing tools for managing specific modem states and configurations.

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: network-manager 1.46.0-1ubuntu2
ProcVersionSignature: Ubuntu 6.8.0-22.22-generic 6.8.1
Uname: Linux 6.8.0-22-generic x86_64
ApportVersion: 2.28.0-0ubuntu1
Architecture: amd64
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Thu Apr 11 11:04:31 2024
InstallationDate: Installed on 2024-04-07 (4 days ago)
InstallationMedia: Ubuntu 24.04 LTS "Noble Numbat" - Daily amd64 (20240407.2)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)
nmcli-nm:
 RUNNING VERSION STATE STARTUP CONNECTIVITY NETWORKING WIFI-HW WIFI WWAN-HW WWAN
 running 1.46.0 connected started full enabled enabled disabled enabled enabled