X1 Carbon WWAN snafu

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X1 Carbon WWAN snafu

Hans-Christian Hartmann
Hi,

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

Thanx!
        Chris
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Re: X1 Carbon WWAN snafu

Bjørn Mork
Hans-Christian Hartmann <[hidden email]> 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 :)


Bjørn
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Re: X1 Carbon WWAN snafu

Henrique de Moraes Holschuh-2
In reply to this post by Hans-Christian Hartmann
On Sat, 18 Feb 2017, Hans-Christian Hartmann wrote:
> 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?

First, you should check the rfkill status of the WWAN device.  If it is
"rfkilled", it won't work and might not even show up in the bus.

The way to do this is distro-dependant, Debian and Ubuntu have an
"rfkill" package with an rfkill tool, and also an urfkill package with a
daemon that presumably listen to some input events related to
rfkill-style keys and switches.

NetworkManager likely has a way to interact with the rfkill subsystem
as well.

Also, try pressing the relevant Fn+Fx hotkey a few times...

--
  Henrique Holschuh
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