Issue connecting with Quectel EM20-G modem on openwrt

[Alex Ballmer]

Hi there,

I have been trying to add support for the Quectel EM20-G LTE modem on
openwrt, using a similar method to how the support for the RM500Q modem
was implemented. I made changes to the qmi_wwan driver using the
attached patch (which also has backported changes for the RM500Q). 

I am currently using modemmanager master commit
1eeec40ee85552cee957f35db9cc85aae6116e48 on linux 4.14. I am running on
openwrt 18.06.2.

The modem is detected successfully by the kernel and libqmi.
Modemmanager seems to detect the modem and sim fine, but the modem is
always listed as "enabled", not "connected" and does not have a bearer.

I attached the output from modemmanager using the --debug and
--log-level=DEBUG flags, plus the patch I used to get qmi_wwan working.

This might also be because of poor signal. I do not have physical
access to the machine with the modem, and it may be having difficulty
reaching the towers.


Output from mmcli:

root at localhost:~# mmcli -m 1
  -----------------------------------
  General  |               dbus path:
/org/freedesktop/ModemManager1/Modem/1 |               device id:
f1d0a27d62687a3e3b17a5ec349a5e77f4d62f45
----------------------------------- Hardware |            manufacturer:
QUALCOMM INCORPORATED |                   model: EM20-G
           |       firmware revision: EM20GRUR01A08M4G
           |          carrier config: VoLTE-ATT
           | carrier config revision: 08010335
           |            h/w revision: 20000
           |               supported: gsm-umts, lte
           |                 current: gsm-umts, lte
           |            equipment id: 864505040018676
  -----------------------------------
  System   |                  device:
/sys/devices/platform/soc/soc:usb30 at 1/10000000.dwc3/xhci-hcd.1.auto/usb4/4-1
|                 drivers: qmi_wwan |                  plugin: Quectel
           |            primary port: cdc-wdm0
           |                   ports: cdc-wdm0 (qmi), wwan0 (net)
  -----------------------------------
  Numbers  |                     own: 13236874124
  -----------------------------------
  Status   |                    lock: sim-pin2
           |          unlock retries: sim-pin (3), sim-pin2 (3),
sim-puk (10), sim-puk2 (10) |                   state: enabled
           |             power state: on
           |          signal quality: 0% (cached)
  -----------------------------------
  Modes    |               supported: allowed: 3g; preferred: none
           |                          allowed: 4g; preferred: none
           |                          allowed: 3g, 4g; preferred: 3g
           |                          allowed: 3g, 4g; preferred: 4g
           |                 current: allowed: 3g, 4g; preferred: 4g
  -----------------------------------
  Bands    |               supported: utran-1, utran-3, utran-6,
utran-5, utran-8, utran-2, |                          eutran-1,
eutran-2, eutran-3, eutran-4, eutran-5, eutran-7, eutran-8, |
               eutran-12, eutran-13, eutran-14, eutran-17, eutran-18,
eutran-19, |                          eutran-20, eutran-25, eutran-26,
eutran-28, eutran-29, eutran-30, |                          eutran-32,
eutran-38, eutran-39, eutran-40, eutran-41, eutran-42, |
          eutran-43, eutran-46, eutran-48, eutran-66 |
current: utran-1, utran-3, utran-5, utran-8, utran-2, eutran-1, |
                   eutran-2, eutran-3, eutran-4, eutran-5, eutran-7,
eutran-8, |                          eutran-12, eutran-13, eutran-14,
eutran-17, eutran-18, eutran-19, |                          eutran-20,
eutran-25, eutran-26, eutran-28, eutran-29, eutran-30, |
          eutran-38, eutran-39, eutran-40, eutran-41, eutran-42,
eutran-43, |                          eutran-46, eutran-48, eutran-66
----------------------------------- IP       |               supported:
ipv4, ipv6, ipv4v6 ----------------------------------- 3GPP     |
             imei: 864505040018676 |            registration: idle
----------------------------------- SIM      |               dbus path:
/org/freedesktop/ModemManager1/SIM/0
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