How to make --nas-set-system-selection-preference='umts|lte' persistent ?

[Aleksander Morgado]

Hey,

On Tue, Nov 4, 2014 at 6:55 AM, Gopakumar Choorakkot Edakkunni
<gopakumar.c.e at gmail.com> wrote:
> So I wanted to disable my modem from trying to connect to 2G because I saw
> some threads that says that Sierra modem firmware conks at times when they
> try to connect to 2G. I have a Sierra AC314U modem.
>
> So I said qmicli -d /dev/cdc-wdm0
> --nas-set-system-selection-preference='umts|lte' - basically saying that use
> only 3G and LTE. After that point the modem goes back to "Ready to connect"
> state.
>
> Now I try using - qmicli -d /dev/cdc-wdm0 --wds-start-network=broadband
> --client-no-release-cid to initiate the connection (which is what I usually
> use to connect and it works). But after that point the modem refuses to
> connect even though the --nas-get-system-info option shows available 3G/LTE
> networks.
>
>
> So I suspected that its because the nas-set-system-selection-preference says
> that a modem reset is needed, and I did not reset the modem. So I forced a
> reset using the below pair of commands, but after the  reset the umts|lte
> selection I made is thrown out and its back to gsm|umts
> lte. So thats a chicken and egg problem.
>
>
> qmicli -d /dev/cdc-wdm0 --dms-set-operating-mode=offline
> qmicli -d /dev/cdc-wdm0 --dms-set-operating-mode=reset
>
> So my question is: If the "--nas-set-system-selection-preference='umts|lte'"
> needs a reset and the setting is wiped out after a reset, how exactly do I
> do that ? Any guidance will be appreciated!

qmicli --nas-set-system-selection-preference uses
QMI_NAS_CHANGE_DURATION_PERMANENT when setting the new selection
preference; which means that the modem is instructed to store it so
that the setting is kept after all reboots.

The offline->reset sequence, for what we know, is only required when
you're e.g. switching from CDMA/EVDO-mode to GSM/UMTS/LTE-mode (in
modems supporting all). That's what we do in ModemManager at least.

For 2G/3G connections there's also the "WCDMA acquisition order
preference" configuration which is also used in the Set System
Selection preference command, *but* qmicli doesn't use it. That
preference allows to say e.g. "3G preferred over 2G", but keep both in
the allowed list. ModemManager and mmcli allows to play with that one,
though.


-- 
Aleksander
https://aleksander.es