[ltp] X1 Carbon WWAN snafu

Bjørn Mork linux-thinkpad@linux-thinkpad.org
Mon, 06 Mar 2017 13:22:28 +0100

Hans-Christian Hartmann <chris.hartmann@snafu.de> writes:

> Hi,
> I have a 4gen X1 Carbon with the Sierra cellular modem (Sierra Wireless
> EM7455 Qualcomm Snapdragon X7 LTE-A).

So do I.

> When I cold boot Linux (Mint 18.1) the mobile broadband is
> "unavailable".  When I cold boot Windows 10 and connect to
> internet.telekom, warm boot Linux, I can reconnect just fine.
> So the Windows driver puts the modem in the right mode (mood? :) and the
> Linux Modem/NetworkManager combo forgets something important.
> What can this be? How can I find out and fix this?

I suspect this is due to the "fcc auth" feature enabled on these
modems. The feature is only supported in recent versions of ModemManager
with equally recent versions of libqmi and libmbim.  You need
ModemManager v1.6 or newer.  Which version do you have? If it is a more
recent version than that, then I think you are better off asking on the
modemmanager list with a debug log from a failing session.

See https://lists.freedesktop.org/mailman/listinfo/modemmanager-devel
and https://www.freedesktop.org/wiki/Software/ModemManager/Debugging/

FWIW, I am using the modem to send this and I removed Windows as soon as
I got the X1.  Too nice hardware to waste :)