cdc-wdmX interface no longer created after reset

[Paul Gildea]

Hi Bjørn et al.,

The issue was indeed that somehow NVRAM settings did change, I was able to
set some of these back to normal and the modem came up as expected.
I've noticed that other settings have changed so the modem is unreliable to
use as of yet.

For instance:

Working MC7455 at default settings:

AT!CUSTOM?
!CUSTOM:
             GPSENABLE		0x01
             GPSLPM		0x01
             SIMLPM		0x01
             USBSERIALENABLE=	0x01
             SINGLEAPNSWITCH	0x01

Broken MC7455:

AT!CUSTOM?
!CUSTOM:
             GPSENABLE		0x01
             UIM2ENABLE		0x01
             SIMLPM		0x01


Thanks for the help!

--
Paul




On 11 October 2017 at 12:36, Bjørn Mork <bjorn at mork.no> wrote:

> Paul Gildea <gildeap at tcd.ie> writes:
>
> > 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?
>
> The only possible reason I see is that there are no RMNET/QMI functions
> and no serial number string descriptor.  Please veriy by doing e.g
>
>  lsusb -vd 1199:9071
>
> Both the RMNET functions and the serial number export are controlled by
> firmware config.  I cannot explain why the configuration changed, but it
> should be easy to fix since you still have AT command access.  Assuming
> that there isn't anything more serious wrong here - unexplained NVRAM
> changes are not good...  You may want to let Sierra Wireless take a look
> at the modem if you have that option.
>
> Please see the documentation of the AT!USBCOMP and AT!CUSTOM commands in
> the "AirPrime EM74xx/MC74xx AT Command Reference" for info on how to
> change the settings back to normal.  I believe the serial number custom
> setting is “USBSERIALENABLE”.
>
>
>
> Bjørn
>
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