Quectel: Allowed modes

[Aleksander Morgado]

Hey!

> > We’re facing a problem where ModemManager (v1.10.0) doesn’t respect the allowed modes when the modem (Quectel BG96) fails to connect the first try.
> >
> > First, we set the allowed modes to 4G (--set-allowed-modes=4g) which works. We verified this by running AT+QCFG=“nwscanmode” which is correctly set to “3” after running the command. When NetworkManager then issues a simple connect, ModemManager launches an automatic network registration which appears to reset the allowed modes. Querying nwscanmode afterwards yields “0” which corresponds to all modes (2g+4g).
> >
> > How can we make the allowed modes setting stick (preferably across module restarts/resets as well)?
>
> So it seems it's this next "NAS Initiate Network Register" the one
> that ends up resetting the nwscanmode setting.
>

It looks like we shouldn't even be using NAS Initiate Network Register
if Set System Selection Preference is supported, because the
functionality of the former is already available in the latter. My
assumption therefore is that if we switch to use SSSP, the mode
preference settings may be preserved.

Anyway, if you could please do the Get System Selection Preference
check before and after the Initiate Network Register, that would be
awesome to confirm this.

-- 
Aleksander
https://aleksander.es