Connect Cinterion modem with SWWAN fails with unknown error

[Dan Williams]

On Fri, 2019-03-15 at 16:34 +0100, Sven Schwermer wrote:
> Hi all,
> 
> > On 15 Mar 2019, at 16:03, matthew stanger <stangerm2 at gmail.com>
> > wrote:
> > 
> > Anyway, the only thing I can think of is a timing issue with the
> > modem
> > firwmare and network registration or initial bearer setup or
> > something
> > like that. Perhaps MM isn't querying some ready state well enough,
> > or
> > the modem isn't fully set up when we're querying because MM isn't
> > asking the right question. NOt sure what else it could be.  
> > Wonderful observation there. Just realized this modem's boot ready
> > URC is '+PBREADY'. There's nothing in MM to support(minus ublox
> > plugin) this cmd, which would imply that MM would be sending cmd's
> > before the module is ready.
> > 
> >  I made sure that the modem was freshly booted in both cases.  
> > That'd be the main difference, you waited.
> > 
> > To test this theory out all you need to do is stop MM, plugin/start
> > your modem give it ~20 sec's to be sure. Then start MM and see if
> > the connection now works. Let me know if that work and then we can
> > go from there.
> 
> I actually tried exactly this: I restarted the modem without
> ModemManager running, sent AT to the modem until I got +PBREADY as
> part of the reply and then started ModemManager. Unfortunately, this
> leads to the same behaviour. Same old +CEER: "SM
> deactivation",187,"Last PDN disconnection not allowed”

Might this imply that we're talking about the initial bearer and that
when MM tries to connect, because it will attempt to close any existing
connection, the modem is telling MM "no"?

We already know we need to be better about auto-detecting that the
initial bearer is active and should probably create a Bearer object to
represent it when we can figure it out. Then perhaps a connection
request for the same APN would just be NOP and return that already
created bearer? (perhaps Aleksander already implemented that, I recall
some discussion about it late last year)

Dan

> Sven
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