Sierra Wireless em7345 disconnects from USB Bus

[Aleksander Morgado]

Hey,

>
> recently we got reports from customers in the Netherlands and some parts
> of Germany that their Sierra Wireless EM7345 modems (all build into
> various Lenovo laptops) stopped working.
>
> In Germany this has so far only be the case for Deutsche Telekom SIM
> cards. I strongly suspect this has something to do with the network
> operators infrastructure, as there are reports, that even within the
> same city some locations reproducibly work and some don't.
>
> Following hints at the Lenovo forums (for example
> https://forums.lenovo.com/t5/ThinkPad-X-Series-Laptops/Sierra-Wireless-EM7345/td-p/2046489)
> we upgraded the firmware which fixed these problems.
>
> The systems in question had been working fine previously (since around
> fall/winter 2015) using the same network operator, all running
> ModemManager on Linux.
>
> The symptoms in short are:
>   * Modem successfully connects to APN
>   * Modem disappears from USB Bus
>   * Modem reappears displaying a usb product string of "1 CDC" and a
> changed vendor ID.
>   * After a reboot the modem is recognized by ModemManager again.
>
> Attached are ModemManager and kernel logs for reference. They are quite
> big, so I had to gzip them.
>

These look like usual modem firmware crashes to me, with the module
rebooting to the Intel vid. There's not much we can do ourselves
unless poking vendors to debug and analyze the issues further :/. I
guess we can only suggest users to upgrade to he 1.2 FW which as you
said fixes the problems. Given that these issues are specific to the
network, they're probably happening due to specific network
configurations that make the firmware crash (CA related maybe?).


-- 
Aleksander
https://aleksander.es