Troubleshooting WWAN card on Lenovo X1 Yoga Gen 8

[Peter Bittner]

Hi there!

I bought a Lenovo X1 Yoga Gen 8 (Type 21HQ) laptop just recently.
Lenovo finally offers them with Ubuntu Linux pre-installed or without
any OS, at your option. (For some reason the 5G WWAN module is only
available when you order Windows or no OS. I chose the latter, and
installed Ubuntu myself.)

I use an Italian FASTWEB sim card in the WWAN slot, and the GNOME
settings GUI displays the hardware device. Unfortunately though, I
can't get the mobile broadband connection to work via the UI. Here's
what I do:

- First, activate the WWAN module from the GNOME settings GUI
(Settings > Mobile Network; I don't see how to do this with `nmcli` or
`mmcli`).
- Then, in the terminal, configure the access point and bring up the connection:

$ sudo nmcli device status
DEVICE             TYPE      STATE                   CONNECTION
wlp0s20f3          wifi      connected               homewifi
docker0            bridge    connected (externally)  docker0
p2p-dev-wlp0s20f3  wifi-p2p  disconnected            --
wwan0mbim0         gsm       unavailable             --
lo                 loopback  unmanaged               --

$ sudo nmcli device status
DEVICE             TYPE      STATE                   CONNECTION
wlp0s20f3          wifi      connected               homewifi
docker0            bridge    connected (externally)  docker0
wwan0mbim0         gsm       disconnected            --
p2p-dev-wlp0s20f3  wifi-p2p  disconnected            --
lo                 loopback  unmanaged               --

$ sudo nmcli connection add type gsm \
    ifname wwan0mbim0 \
    con-name "FW WEB MOBILE" \
    gsm.apn apn.fastweb.it \
    connection.autoconnect yes
Connection 'FW WEB MOBILE' (c7acc26c-b243-487b-bfb2-d80c654958a7)
successfully added.

$ sudo nmcli connection up "FW WEB MOBILE" ifname wwan0mbim0
Error: Connection activation failed: The base network connection was interrupted
Hint: use 'journalctl -xe
NM_CONNECTION=c7acc26c-b243-487b-bfb2-d80c654958a7 +
NM_DEVICE=wwan0mbim0' to get more details.

- Now the WWAN device starts flapping. The UI shows "Mobile Broadband
Connecting" and "Mobile Broadband Off", changing all the time. The
journal shows the following:

$ journalctl -xe NM_CONNECTION=c7acc26c-b243-487b-bfb2-d80c654958a7 +
NM_DEVICE=wwan0mbim0

Feb 18 22:38:31 bittner NetworkManager[1217]: <info>
[1708292311.3157] device (wwan0mbim0): Activation: starting connection
'FW WEB MOBILE' (c7acc26c-b243-487b-bfb2-d80c654958a7)
Feb 18 22:38:31 bittner NetworkManager[1217]: <info>
[1708292311.3157] device (wwan0mbim0): state change: disconnected ->
prepare (reason 'none', sys-iface-state: 'managed')
Feb 18 22:38:31 bittner NetworkManager[1217]: <info>
[1708292311.3292] device (wwan0mbim0): state change: prepare ->
disconnected (reason 'user-requested', sys-iface-state: 'managed')
Feb 18 22:38:31 bittner NetworkManager[1217]: <info>
[1708292311.3301] device (wwan0mbim0): Activation: starting connection
'FW WEB MOBILE' (c7acc26c-b243-487b-bfb2-d80c654958a7)
Feb 18 22:38:31 bittner NetworkManager[1217]: <info>
[1708292311.3301] device (wwan0mbim0): state change: disconnected ->
prepare (reason 'none', sys-iface-state: 'managed')
Feb 18 22:38:31 bittner NetworkManager[1217]: <info>
[1708292311.3441] device (wwan0mbim0): state change: prepare ->
disconnected (reason 'user-requested', sys-iface-state: 'managed')
...

I can only disable the device again to stop the CPU going havoc. What
do I do wrong?

Any hint is greatly appreciated,
Peter