Locking MM to 4g only

[Dan Williams]

On Thu, 2017-02-16 at 17:36 +0100, Aleksander Morgado wrote:
> On Thu, Feb 16, 2017 at 4:29 PM, Russ Westrem
> <lspwaterproofing at gmail.com> wrote:
> > Im am trying to lock to 4g only.
> > 
> >   Modes    |      supported: 'allowed: 2g, 3g, 4g; preferred: none'
> >            |        current: 'allowed: 2g, 3g, 4g; preferred: none'
> > 
> > 
> > 
> > root at LEDE:~# mmcli -m 0 --set-allowed-modes=4g
> > error: couldn't set current modes:
> > 'GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Unsupported:
> > Cannot
> > change modes: only one combination supported'
> 
> Is this in MBIM mode? There isn't any support for mode/capabilities
> changing in plain MBIM mode. If this is in QMI mode, try
> --set-current-capabilities=lte instead. ModemManager only exposes the
> list of mode combinations that are allowed by the modem in the
> current
> capability. See
> https://sigquit.wordpress.com/2013/06/03/changing-modes-and-capabilit
> ies-in-modemmanager/
> 
> > root at LEDE:~# mmcli -m 0 --set-preferred-mode=4g
> > error: setting preferred mode requires list of allowed modes
> 
> --preferred-mode must be given with --allowed-modes. E.g. there may
> be
> a combination saying "allowed 2G, 3G and 4G" but preferred "4G".

It's probably Russ's 7455 in QMI mode?

For QMI MM doesn't allow specific mode selection/enablement either, see
the QMI implementation of modem_load_supported_modes().  If the modem
supports NAS >= 1.21 (or slightly earlier) then with
NASSystemSelectionPreference we could use the ordered radio interface
list to pass to TLV 0x1E (AcquisitionOrder).

libqmi doesn't support that, but I just did a patch for it.  However, I
can't quite figure out the relationship between "Mode Preference" and
the radio interface order array for the TLV I added.  Maybe somebody
else can test and find out?

Dan