[ltp] Re: Sierra Wireless EM7345 4G LTE

Bjørn Mork linux-thinkpad@linux-thinkpad.org
Wed, 18 Jun 2014 10:30:08 +0200

Vincent Bernat <bernat@luffy.cx> writes:
>  ❦ 18 juin 2014 01:31 +0200, Vincent Bernat <bernat@luffy.cx>=
>> I am trying to make the LTE modem shipped with the second gen carbon X1
>> works. I have found the following thread saying that it should work:
>>  http://linux-thinkpad.10952.n7.nabble.com/2nd-gen-X1-carbon-3g-lte-Sier=
>> However, I am unable to get any /dev/cdc* device.
>> [ 9358.677017] cdc_ncm 1-4:1.0: MAC-Address: ff:ff:ff:ff:ff:ff
>> [ 9358.677860] cdc_ncm 1-4:1.0 usb0: register 'cdc_ncm' at usb-0000:00:1=
4 .0-4, CDC NCM, ff:ff:ff:ff:ff:ff
>> [ 9358.678148] usbcore: registered new interface driver cdc_ncm
>> [ 9358.679842] usbcore: registered new interface driver cdc_wdm
>> [ 9358.680771] usbcore: registered new interface driver cdc_mbim
>> Linux zoro 3.15-rc8-amd64 #1 SMP Debian 3.15~rc8-1~exp1 (2014-06-03) x86=
_64 GNU/Linux
>> So, I suppose the problem is that cdc_ncm kicks first. How can I switch
>> to another mode? I have the usb0 interface:
>> 8: usb0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAU=
LT group default qlen 1000
>>     link/ether ff:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
> After some digging, I have discovered that I can load cdc_ncm with
> "prefer_mbim=Y". I get a /dev/cdc-wdm1 device and Modem Manager is able
> to setup the connection without a problem!

Yes, I haven't found any way to use this modem in NCM mode, and my
current theory is that this mode is not supported despite being
"announced" by the firmware.  This theory is supported by the fact that
Lenovo provide an MBIM driver for older Windows versions where MBIM
isn't natively supported.

So "prefer_mbim=Y" is definitely the answer for this particular modem.

I must admit that I did not anticipate a situation like this when adding
that module option. So that's why it is a global module option instead
of something you can configure per device.  But I'm hoping that won't
cause problems for anyone.