Modem SIMCom SIM7600 failed

[Aleksander Morgado]

Hey!

> On 17/01/2020 09:56, Aleksander Morgado wrote:
> > Hey,
> >
> >> Using ModemManager (version 1.10.8) with modem SIMCom SIM7600G, it
> >> failed to probe it at boot time.
> >> If I stop ModemManager and wait a while and then restart it probes it
> >> better.
> >> With newest modem firmware it is ok. But I wonder why ModemManager do
> >> not re-probe it and it failed ?
> >>
> > Looks like the device was not able to reply to any QMI message during
> > the first initial 20s after bootup:
> > Jan 16 11:19:15 ws-box-v1.1 ModemManager[176]: <debug>
> > (usbmisc/cdc-wdm0) error checking QMI support: 'Transaction timed out'
> >
> > I guess we could still update this value even more so that the probing
> > attempts end up taking longer.
> >
> > Is this issue happening consistently? Or did it happen randomly?
> This is consistently and mainly related to firmware version of the modem.
> We are in contact in parallel with SIMCom to get proper explanation.
> >
> > Would you be able to update the timeout to a value greater than 20s,
> > e.g. 30s, and see if that solves the problem? The change would be
> > equivalent to this one:
> > https://gitlab.freedesktop.org/mobile-broadband/ModemManager/commit/a73b13b67cd1987431f92ea6a4ccc2cb85c51cc7
> Thanks for pointing this patch. I could change the retries value and get
> the modem working.
>

How much bigger did you need to put the timeout to get the probing
work reliably? Was 30s enough? If you can talk to SIMCom, please ask
them how long the device needs between the ports are exposed in USB
until they can be properly used with QMI commands.

>
> Still a question, where could I redo the probing at the end of the probe
> loop if not device was found ?
>

You could probably try running "mmcli --scan-modems" to trigger a
rescan, although that command was totally not done for the purpose
you're looking for :D The correct fix for your problem would be to
wait long enough until the port probing succeeds, but we cannot
blindly put an extremely long timeout there because it could affect
the probing time in other devices (e.g. if we end up seeing a cdc-wdm
port that fails constantly to every probing attempt, as we saw with
the MC7354 interface #11 IIRC before it was ignored explicitly in the
kernel)

-- 
Aleksander
https://aleksander.es