Sierra MC7354: Drowning in "bearer verbose call end reason (6,36): [3gpp] regular-deactivation"

[Einar Jón]

Hello

I am using the Sierra MC7354 modem, and we are getting unusual
disconnects on AT&T in the US. Vodafone is fine on the same modems,
and this only seems to happen on 4G. AT&T 3G  seems to work.

We start out connected, but  after a bit of time we hit
"gsm-wcdma-regular-deactivation/[3gpp] regular-deactivation", and then
we're spamming the log file with those messages (up to 240 lines/sec).
Logs below.
Similar to this post, but seems mostly unrelated.
https://lists.freedesktop.org/archives/modemmanager-devel/2017-February/003988.html
We opening/closing PDP connections during this period, but there is no
connectivity.

Questions:
1) Any ideas what is happening?
2) should I be calling ifdown when I hit 'state changed (connected ->
registered)' ?

We have been in touch with both Sierra and AT&T, but they say that
libQMI is unsupported. so there is not much help there.

Setup
Sierra MC7354 modem
ModemManager 1.6.2
libQmi 1.16.0
Arm linux - kernel 3.14

I'm using buildroot, so upgrading libQmi  (to 1.18.0 or 1.20.0) and
ModemManager (to 1.6.8 or 1.8.0) would be doable. Are there any
additional benefits in the newer versions regarding this issue?
------------------------------
<Normal connect procedure>
Aug  6 07:14:44 armxl ModemManager[932]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (connecting ->
connected)
<snip - Connected and reachable>
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer verbose call
end reason (6,36): [3gpp] regular-deactivation
Aug  6 08:07:37 armxl ModemManager[932]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (connected ->
registered)
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer verbose call
end reason (6,36): [3gpp] regular-deactivation
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer verbose call
end reason (6,36): [3gpp] regular-deactivation
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer verbose call
end reason (6,36): [3gpp] regular-deactivation
Aug  6 08:07:37 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
<snip - 8 sec:approx 1850 log lines of "regular-deactivation">
Aug  6 08:07:45 armxl ModemManager[932]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (registered ->
connecting)
Aug  6 08:07:45 armxl ModemManager[932]: <info>  QMI IPv4 Settings:
Aug  6 08:07:45 armxl ModemManager[932]: <info>      Address: X.X.X.X/29
Aug  6 08:07:45 armxl ModemManager[932]: <info>      Gateway: X.X.X.X
Aug  6 08:07:45 armxl ModemManager[932]: <info>      DNS #1: X.X.X.X
Aug  6 08:07:45 armxl ModemManager[932]: <info>      DNS #2: X.X.X.X
Aug  6 08:07:45 armxl ModemManager[932]: <info>         MTU: 1430
Aug  6 08:07:45 armxl ModemManager[932]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (connecting ->
connected)
Aug  6 08:08:14 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
Aug  6 08:08:14 armxl ModemManager[932]: <info>  bearer verbose call
end reason (6,36): [3gpp] regular-deactivation
Aug  6 08:08:14 armxl ModemManager[932]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (connected ->
registered)
Aug  6 08:08:14 armxl ModemManager[932]: <info>  bearer call end
reason (1008): 'gsm-wcdma-regular-deactivation'
Aug  6 08:08:14 armxl ModemManager[932]: <info>  bearer verbose call
end reason (6,36): [3gpp] regular-deactivation
<snip - 8 sec:approx 1850 log lines of "regular-deactivation">
Aug  6 08:08:22 armxl ModemManager[932]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (registered ->
connecting)

--
Regards
Einar Jón