cdc-wdmX interface no longer created after reset

[Paul Gildea]

This may be outside the scope of here. I have been testing sending commands
rapidly with qmicli and as part of that I am resetting the modem (MC7455).
On one occasion (and ever since) the modem did not come back up in the
correct way. No cdc-wdm interface was created. I also noticed in dmesg that
the product was now a different string and that the serial number was no
longer displayed.

For instance here is a working MC7455 being detected on my system:

[   34.921127] usb 2-1: New USB device found, idVendor=1199, idProduct=9071

[   34.921129] usb 2-1: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[   34.921132] usb 2-1: Product: Sierra Wireless MC7455
Qualcomm\xffffffc2\xffff
[   34.921134] usb 2-1: Manufacturer: Sierra Wireless, Incorporated

[   34.921135] usb 2-1: SerialNumber:  LQ64644441021010
[   34.923104] qcserial 2-1:1.0: Qualcomm USB modem converter detected

[   34.923201] usb 2-1: Qualcomm USB modem converter now attached to
ttyUSB3
[   34.924140] qcserial 2-1:1.2: Qualcomm USB modem converter detected

[   34.924237] usb 2-1: Qualcomm USB modem converter now attached to
ttyUSB4
[   34.925127] qcserial 2-1:1.3: Qualcomm USB modem converter detected

[   34.925217] usb 2-1: Qualcomm USB modem converter now attached to
ttyUSB5
[   34.925844] qmi_wwan 2-1:1.8: cdc-wdm0: USB WDM device

[   34.926069] qmi_wwan 2-1:1.8 wwan0: register 'qmi_wwan' at
usb-0000:00:14.0-1
[   34.927048] qmi_wwan 2-1:1.10: cdc-wdm1: USB WDM device

[   34.927238] qmi_wwan 2-1:1.10 wwan1: register 'qmi_wwan' at
usb-0000:00:14.0-


Here is the new output where the cdc-wdm interface is not created:


[   34.784426] usb 2-3: New USB device found, idVendor=1199, idProduct=9071

[   34.784428] usb 2-3: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[   34.784430] usb 2-3: Product: MC7455

[   34.784432] usb 2-3: Manufacturer: Sierra Wireless, Incorporated

[   34.786401] qcserial 2-3:1.0: Qualcomm USB modem converter detected
[   34.786504] usb 2-3: Qualcomm USB modem converter now attached to ttyUSB0
[   34.787384] qcserial 2-3:1.2: Qualcomm USB modem converter detected
[   34.787475] usb 2-3: Qualcomm USB modem converter now attached to ttyUSB1
[   34.788347] qcserial 2-3:1.3: Qualcomm USB modem converter detected
[   34.788439] usb 2-3: Qualcomm USB modem converter now attached to
ttyUSB2

The only differences I can see are that the "Product:" has changed and the
"SerialNumber:" is missing. When I check the device path the Serial file is
not there. I can connect to the device and send AT commands no problem as
the USB interfaces are enumerated. Any idea what may have caused this?
Modem is no longer usable with qmicli, for some reason qmi_wwan is not
creating the interface?

Regards,

--
Paul
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