ModemManager and sleep

[Aleksander Morgado]

Hey,

> I'm using Ubuntu 18.04.3 lts on a Lenovo Thinkpad X1 carbon i7-6600 with modem LTE Sierra ID_MODEL=Sierra_Wireless_EM7455_Qualcomm_Snapdragon_X7_LTE-A.
> When the laptop is power up I can use the modem, but when the laptop went to sleep and after I resume it, the modem disappear.
> Now the laptop is resumed and the modem is not available to ModemManager 'cause this error:
>
> root at angelo-thinkpad-x1-carbon-4th:~# systemctl status ModemManager
> ● ModemManager.service - Modem Manager
>    Loaded: loaded (/lib/systemd/system/ModemManager.service; enabled; vendor preset: enabled)
>    Active: inactive (dead) since Sat 2019-12-07 16:52:35 CET; 30min ago
>   Process: 13379 ExecStart=/usr/sbin/ModemManager --filter-policy=strict (code=exited, status=0/SUCCESS)
>  Main PID: 13379 (code=exited, status=0/SUCCESS)
>
> dic 07 16:52:35 angelo-thinkpad-x1-carbon-4th systemd[1]: Starting Modem Manager...
> dic 07 16:52:35 angelo-thinkpad-x1-carbon-4th ModemManager[13379]: <info>  ModemManager (version 1.10.0) starting in system bus...
> dic 07 16:52:35 angelo-thinkpad-x1-carbon-4th ModemManager[13379]: <warn>  Could not acquire the 'org.freedesktop.ModemManager1' service name
> dic 07 16:52:35 angelo-thinkpad-x1-carbon-4th ModemManager[13379]: <info>  ModemManager is shut down
> dic 07 16:52:35 angelo-thinkpad-x1-carbon-4th systemd[1]: Started Modem Manager.
>

That error above is weird, were you running ModemManager manually
yourself at some point? It doesn't make sense that the systemd started
service ends up failing like that unless there was another
ModemManager process around.

The issue with not being available after suspend may be a timing
issue, I would definitely try with a newer ModemManager version (e.g.
1.12) if possible. I maintain a PPA for Ubuntu 18.04 here, but I
didn't upgrade the MM there to 1.12 yet. Anyway, that PPA also
contains newer libqmi/libmbim, so I would definitely try using that
PPA and see what happens:
https://launchpad.net/~aleksander-m/+archive/ubuntu/modemmanager-bionic

Will try to upgrade MM in the PPA soon, but cannot promise.

-- 
Aleksander
https://aleksander.es