Sierra Wireless EM7455

Bjørn Mork bjorn at
Wed Jun 1 07:25:56 UTC 2016

Ralph Plawetzki <ralph at> writes:

>> Stefan Armbruster <ml001 at> writes:
>>    qmicli -p -d /dev/cdc-wdm0 --device-open-mbim --dms-set-fcc-authentication
> Hi list,
> I still have problems to get the modem connect to the net.
> libqmi and libmbim are compiled from the qmi-over-mbim branches.
> sudo qmicli -v -p -d /dev/cdc-wdm0 --device-open-mbim
> --dms-set-fcc-authentication works and gives me

So that looks good.  It returns NoEffect, but I assume that is because
you've already sent the command.

> Nevertheless when I try to connect with network manager, it gets a local IP:
> [rallo at six ~]$ ifconfig wwp0s20f0u2i12
> wwp0s20f0u2i12: flags=4291<UP,BROADCAST,RUNNING,NOARP,MULTICAST>  mtu 1500
>         inet  netmask  broadcast
>         ether aa:52:d6:06:f1:06  txqueuelen 1000  (Ethernet)
>         RX packets 0  bytes 0 (0.0 B)
>         RX errors 0  dropped 0  overruns 0  frame 0
>         TX packets 17  bytes 2285 (2.2 KiB)
>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
> [rallo at six ~]$
> What is going on here? Is there anything that I can do to analyze this
> further?

I don't know why this doesn't work.  It should...

So I'm afraid we are over in the black magic "let's try anything"
department, unless someone else sees anything missing.  The first I can
think of is that I've sometimes seen weird "dead endpoint" behaviour on
my MC7455 being resolved by a USB reset.  This has been affecting the
serial functions for me, but maybe the problem applies to MBIM too?

Alan Stern wrote a very useful "usbreset" debug tool a long time ago.  I
believe it's included in recent usbutils.  But if you don't have it,
then the OpenWrt version is even nicer since they've improved it with
device ID matching.  They just forgot(?) to include stdlib.h.  Get and
run it like this, replacing the device ID with yours (1199:9078?):

bjorn at nemi:/tmp$ wget ';a=blob_plain;f=package/utils/usbreset/src/usbreset.c;hb=HEAD' --content-disposition
--2016-06-01 09:18:02--;a=blob_plain;f=package/utils/usbreset/src/usbreset.c;hb=HEAD
Resolving (
Connecting to (||:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 4908 (4.8K) [text/x-csrc]
Saving to: ‘usbreset.c’

usbreset.c                             100%[==========================================================================>]   4.79K  --.-KB/s    in 0s      

2016-06-01 09:18:02 (57.5 MB/s) - ‘usbreset.c’ saved [4908/4908]

bjorn at nemi:/tmp$ sed -i -e '/stdbool/a #include <stdlib.h>' usbreset.c
bjorn at nemi:/tmp$ gcc -o usbreset usbreset.c 
bjorn at nemi:/tmp$ ./usbreset 1199:9071
Resetting MC7455 ... ok

Note: you will have to run it as root unless you have permissions for
/dev/bus/usb set up like me..

This should cause a USB reset, which will *not* reset the EM7455.  But
it will be rediscovered by Linux and ModemManager as a new device, so
you will have to reconnect.  Does it make any difference?

It's a long shot...


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