Sierra Wireless EM7355

Bjørn Mork bjorn at
Thu Jun 19 10:55:10 PDT 2014

Erinn Looney-Triggs <erinn.looneytriggs at> writes:

> This modem is acting pretty erratically to be honest, sometimes it
> appears modemmanager detects it on boot, sometimes not. No particular
> rhyme or reason that I can divine at this point.
> I don't believe anything else is using the device, best way I know to
> check for this is lsof of /dev/cdc-wdm0, and nothing is showing.
> So on this boot the modem doesn't appear to be detected by
> modemmanager, though dmesg shows a listing for it being detected:
> dmesg | grep cdc
> [    3.661711] usbcore: registered new interface driver cdc_ncm
> [    3.663117] usbcore: registered new interface driver cdc_wdm
> [    3.668520] cdc_mbim 3-10:2.12: cdc-wdm0: USB WDM device
> [    3.668686] cdc_mbim 3-10:2.12 wwan0: register 'cdc_mbim' at
> usb-0000:00:14.0-10, CDC MBIM, d6:97:d6:76:77:18
> [    3.668704] usbcore: registered new interface driver cdc_mbim
> sudo mmcli -L
> No modems were found

Is the modem completely dead at this point, or can you actually talk to
it using mbimcli (after stopping ModemManager)?  If you can, does MM
detect the modem if MM is restarted?

I see from the log you sent previously that MM gives up really fast, and
that the version in F20 seems to be a git snapshot from 20130913.  Is
this correct, and will this cause problems, Dan/Alexander?

> I'll read up on usbmon, and any other suggestions are appreciated.

I'd really like to have these problems sorted out, so I appreciate it if
you continue to debug the MBIM problems. But if you depend on the modem
and want a quick-fix, then I assume switching it to QMI mode will help.
I don't know F20 so I don't know if this is applicable, but an udev rule
similar to this used do the job in the good old days:

  ATTR{idVendor}=="1199",ATTR{idProduct}=="901f",ATTR{bConfigurationValue}=="2" ATTR{bConfigurationValue}="1"

This will force the modem to USB configuration #1.  You'll then need the
patch Dan referred to, but IIUC you already had a new enough kernel.


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