Restrict modem (EC21) one of 3G or 4G - ModemManager 1.10.0 (Debian Buster)

[Brendan Simon (eTRIX)]

On 19/08/2020 2:13 am, Aleksander Morgado wrote:
>> This may be a known issue with QMI modems where the internal network
>> registration attempt is done with "QMI NAS Register In Network"; this
>> command not only registers in network, it also makes the access tech
>> preference fallback to "any", and MM doesn't consider that in its API.
>>
>> There is a recent patch to avoid this, by avoiding the use of "NAS
>> Register in Network" and use "NAS Set System Selection Preference"
>> instead: https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/commit/c70b3557184fdf1472ff0cb36e9fd937cc7f9024
>>
>> That patch is not yet in any release, though, not even in 1.14.0. I'll
>> backport it to the 1.14.x branch so that it gets into 1.14.2.
>>
>>
>> So the 64 million dollar question is when is 1.14.2 likely to be released ?
>>
> Sometime in the next few weeks I'd say.

So it's been a while, but I now have MM 1.14.2 installed on my embedded 
system via Debian Buster Backports repo.

I can successfully set the allowed mode to "3G" and get a UMTS connection.

*    mmcli -m 0 --set-allowed-modes="3G"*

However, if I try to lock to 4G the connection never succeeds.
**
     mmcli -m 0 --set-allowed-modes="4G"**

The only way I can get an LTE connection is with the following.
**
     mmcli -m 0 --set-allowed-modes="3G|4G" --set-preferred-mode=4G**

*I presume this is a bug?  But maybe there is something else going on**?**
**Any ideas or suggestions to get an LTE connection with setting 4G as 
the only allowed mode?*

Also, I've just noticed that 1.14.6 has just hit the Buster Backport 
repo.  I'm not sure if that will help or not, but I don't see anything 
in the NEWS file that would suggest a change in this area.

https://github.com/freedesktop/ModemManager/blob/mm-1-14/NEWS

Thanks, Brendan.

****

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