Upgrade from 1.18 to 1.21.1 causes change in behavior

VT102 VT102 at protonmail.com
Thu Nov 24 14:26:47 UTC 2022

Hello all,

I am working with an mPCI Telit LE910C4 modem connected to a Linux System on a Chip running Ubunut 20.04.

With 1.18 ModemManager installed I noticed that serial ports were being listed as ignored except for a GPS port was available through a tty, this meant I couldnt issue AT commands. I also needed bit error rate from the mmlib-glib API so I decided to build ModemManager 1,21.

Upon upgrading the modem no longer recognizes as a qmi device, but the AT command tty terminals are available. I was hoping for some advice on how to investigate this behavior. I did not build libqmi from source because whenever I try to compile on the device compilation freezes (overnight) on compiling certain *.o files. However, I am able to get the modem connected.

Any advice on how to debug why the modem is no longer being recognized as a qmi device?
I am wondering if I need to change the USB configuration of the modem,but this seems likee it would be strange, as it was interacting with the modem via qmi previously via cdc_wdm0.

Below I will post output from mmcli from version 1.21 with QMI not working.


General | path: /org/freedesktop/ModemManager1/Modem/0
| device id:
Hardware | manufacturer: Telit
| model: LE910C4-NF
| firmware revision: 25.21.660-P0F.661806
| supported: gsm-umts, lte
| current: gsm-umts, lte
| equipment id:
System | device: /sys/devices/platform/soc at 0/32c00000.bus/32e50000.usb/ci_hdrc.1/usb1/1-1/1-1.2
| drivers: option, qmi_wwan
| plugin: telit
| primary port: ttyUSB2
| ports: ttyUSB0 (ignored), ttyUSB1 (gps), ttyUSB2 (at),
| ttyUSB3 (at), ttyUSB4 (ignored), wwan0 (ignored)
Status | unlock retries: sim-pin (3), sim-puk (10), sim-pin2 (10), sim-puk2 (10)
| state: connected
| power state: on
| access tech: lte
| signal quality: 85% (recent)
Modes | supported: allowed: 2g; preferred: none
| allowed: 3g; preferred: none
| allowed: 2g, 3g; preferred: none
| allowed: 4g; preferred: none
| allowed: 2g, 4g; preferred: none
| allowed: 3g, 4g; preferred: none
| allowed: 2g, 3g, 4g; preferred: none
| current: allowed: 3g, 4g; preferred: none
IP | supported: ipv4, ipv6, ipv4v6
3GPP | imei:
| operator id: 310410
| operator name: AT&T
| registration: roaming
| packet service state: attached
3GPP EPS | ue mode of operation: csps-2
SIM | primary sim path: /org/freedesktop/ModemManager1/SIM/0
-------------------------------- Bearer | paths: /org/freedesktop/ModemManager1/Bearer/0

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