Detecting Dual SIM on EM7455

Jack Broderick jbroderick at
Tue Apr 6 21:32:47 UTC 2021


I have recently upgraded to 1.16.2 on OpenWRT in order to utilize the
extended SIM features. We integrate both the EM7511 and EM/MC7455. We have
identified that on boot, the EM7511 will detect both SIM's installed, with
the EM7455, however, it requires switching between the slots to detect. We
previously identified this issue when using just qmicli in order to read
the SIM slots.

We resolved this issue by "toggling" the SIM slot on boot so qmicli would
pick up both slots. It is a bit of a hack, but it works. This becomes an
issue, when using AT!IMPREF="AUTO-SIM", and using two SIM's that use
different profiles. For example, if SIM1=AT&T and SIM2=GENERIC, when
switching SIM's the modem appears to reboot. It is not just a reprobe by
ModemManager, the usb device detaches and re-attaches.

The interesting thing is, with the EM7511, both SIM's are reported by both
mmcli and qmicli without needing to "toggle". I am curious if this issue
has been seen in any other testing.

EM7455 After Boot, with modem on SIM1 before reboot:
  SIM      |        primary sim path: /org/freedesktop/ModemManager1/SIM/0
           |          sim slot paths: slot 1:
/org/freedesktop/ModemManager1/SIM/0 (active)
           |                          slot 2: none

After running mmcli -m 0 --set-primary-sim-slot=2

  SIM      |        primary sim path: /org/freedesktop/ModemManager1/SIM/2
           |          sim slot paths: slot 1:
           |                          slot 2:
/org/freedesktop/ModemManager1/SIM/2 (active)

The modem did not reset because AT!IMPREF="GENERIC" was set, the modem did
re-enumerate in modemanager, however.

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