Quectel EC21 QMI transaction problem

[Aleksander Morgado]

Hey,

> we got a Quectel EC21 in a location with bad reception (4G (mostly) not available, using 2G as fallback, connection still unstable). The system works nicely for a while until we encounter the situation below from which it never recovers.
>
> Jan 18 15:50:43 CloudGateway01 ModemManager[188]: transaction 0x71e aborted, but message is not abortable
> Jan 18 15:50:43 CloudGateway01 ModemManager[188]: transaction 0xf aborted, but message is not abortable
> Jan 18 15:50:43 CloudGateway01 ModemManager[188]: <warn>  [modem0/bearer0] checking if connected failed: Transaction timed out
> Jan 18 15:50:43 CloudGateway01 ModemManager[188]: <warn>  [modem0] could not load SIM identifier: QMI operation failed: Transaction timed out
> Jan 18 15:50:43 CloudGateway01 ModemManager[188]: <warn>  [modem0] (quectel) couldn't check SIM swap: QMI operation failed: Transaction timed out
> Jan 18 15:50:48 CloudGateway01 ModemManager[188]: transaction 0x71f aborted, but message is not abortable
> Jan 18 15:50:48 CloudGateway01 ModemManager[188]: <warn>  [modem0/bearer0] checking if connected failed: Transaction timed out
> Jan 18 15:50:53 CloudGateway01 ModemManager[188]: transaction 0x720 aborted, but message is not abortable
>
> Our current workaround is a reboot after which the system works again for some time.
> Has anyone seen this before or could offer some advice (i'd like to find a more gracious method of recovery than a reboot)?
>

That totally looks like the control port going silent. There may be
multiple reasons for this, but in my experience, the most common case
is a crash in the modem firmware of some sort :/

Do you have a way to just reboot the modem instead of the full system?
Just to rule out this is not some MM side effect, have you tried to
just reboot the MM daemon to see if it recovers?
Also, make sure you use the latest firmware from the vendor.

If this issue is easily reproducible, talk to your Quectel support,
because using Quectel QLog you could gather modem logs for them to
analyze, if this is really a crash.

-- 
Aleksander
https://aleksander.es