HP lt4120 failing to make single-stack connections on LTE using MM

[Aleksander Morgado]

>
>>     $ sudo mmcli -m 0 --reset
>
> Thanks - I had overlooked that one, but it doesn't quite work:
>
> error: couldn't reset the modem: 'GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Unsupported: Cannot reset the modem: operation not supported'
>

Oh wow, which MM are you using? This has been implemented for QMI
modems since a very long time ago.

> (Similar result with --factory-reset=123456.)
>
> That said, now that I thought to search for «factory» I realised there's
> «qmicli --dms-restore-factory-defaults». That's probably even better than
> just a powercycle, considering my goal is to have a way to bring it back
> to a clean slate. Luckily the required code was easy to guess: 000000.
>
> However it says «Device needs to get power-cycled for reset to take effect».
>
> «qmicli --dms-set-operating-mode=low-power» followed by
> «qmicli --dms-set-operating-mode=online» does not do the trick, and if I
> use «offline» instead of «low-power» I can't bring it back to «online»
> again as it fails with «QMI protocol error (60): 'InvalidTransition'».
>
> Are there any other ways to powercycle a modem?
>

The correct sequence is: --dms-set-operating-mode=offline and
--dms-set-operating-mode=reset :) That is what MM does when you run
"mmcli -m 0 --reset"

-- 
Aleksander
https://aleksander.es