Quectel: Allowed modes

[Fredrik Flornes Ellertsen]

>
>
> 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.
>

Hi Aleksander! Thanks for your quick reply. I'm working with Sven on this
one.

Yes, it seems the settings in Get System Selection Preference are also
reset
when the network scan times out. Here is the qmicli output just after
setting
the allowed mode to 4G:

$ mmcli -m 0 --set-allowed-modes 4g
successfully set current modes in the modem
$ qmicli -d /dev/cdc-wdm0 -p --nas-get-system-selection-preference
[/dev/cdc-wdm0] Successfully got system selection preference
Emergency mode: 'no'
Mode preference: 'lte'
Band preference: 'gsm-dcs-1800, gsm-900-extended, gsm-900-primary, gsm-850,
gsm-pcs-1900'
LTE band preference: '1, 2, 3, 4, 5, 8, 12, 13, 17, 18, 19, 20, 26, 28, 39'
Network selection preference: 'automatic'
Service domain preference: 'cs-ps'
GSM/WCDMA acquisition order preference: 'gsm'
Acquisition order preference: lte, none, none, gsm

After timeout and the new Initiate Network Register:

$ qmicli -d /dev/cdc-wdm0 -p --nas-get-system-selection-preference
[/dev/cdc-wdm0] Successfully got system selection preference
Emergency mode: 'no'
Mode preference: 'gsm, lte'
Band preference: 'gsm-dcs-1800, gsm-900-extended, gsm-900-primary, gsm-850,
gsm-pcs-1900'
LTE band preference: '1, 2, 3, 4, 5, 8, 12, 13, 17, 18, 19, 20, 26, 28, 39'
Network selection preference: 'automatic'
Service domain preference: 'cs-ps'
GSM/WCDMA acquisition order preference: 'gsm'
Acquisition order preference: lte, none, none, gsm

I just noticed that after completing the procedure above, I am unable to
use mmcli
to set the preferred mode at all. Polling nwscanmode returns '0'. This is
fixed by
restarting ModemManager.

$ mmcli -m 0 --set-allowed-modes 4g
successfully set current modes in the modem
$ qmicli -d /dev/cdc-wdm0 -p --nas-get-system-selection-preference
[/dev/cdc-wdm0] Successfully got system selection preference
Emergency mode: 'no'
Mode preference: 'gsm, lte'
Band preference: 'gsm-dcs-1800, gsm-900-extended, gsm-900-primary, gsm-850,
gsm-pcs-1900'
LTE band preference: '1, 2, 3, 4, 5, 8, 12, 13, 17, 18, 19, 20, 26, 28, 39'
Network selection preference: 'automatic'
Service domain preference: 'cs-ps'
GSM/WCDMA acquisition order preference: 'gsm'
Acquisition order preference: lte, none, none, gsm

Thanks,
Fredrik
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/modemmanager-devel/attachments/20200702/f6141bcf/attachment.htm>