Re: Dell wwan 5560 not working in Fedora 18

[Dan Irwin <rummymobile gmail com>]

Hello Bjørn,

Very informative email. You are spot on, it was the NCM/MBIM problem.

After following your suggestions, the wwan card now works perfectly.

For some reason, NetworkManager (or maybe nm-applet) did not pick up the interface after loading cdc_nbm. A reboot seems to have solved that.

Thank you very much!

Dan

On Mon, Apr 15, 2013 at 5:19 PM, Bjørn Mork <bjorn mork no> wrote:

Dan Irwin <rummymobile gmail com> writes:

> Hello,
>
> I have a dell 3g "wwan" 5560 card in my laptop, which is detected, but does
> not connect to the Internet. The card appears as wwan0 to my system.
>
> ModemManager seems to open ttyACM1 and ttyACM2 (but not ttyACM0), and
> dhclient is started on wwan0.
>
> After sending DHCPDISCOVER 4 times, NetworkManager seems to give up.
>
> I'm not sure what is meant to happen here. I assume the card negotiates
> with the network, and present's an ethernet interface (and presumably a
> dhcp server) to the OS. However, something somewhere is broken.
>
> This configuration appears to work in Windows 7, and I think it also worked
> in Fedora 17, but I'm not 100% sure.
>
> Short of re-installing F17, is there anything obvious I should look for?

I believe the Dell 5560 is a re-branded Ericsson F5321?  If this is a
new laptop, or you have recently upgraded the wwan firmware, then you
may have hit the "NCM/MBIM problem".

Do you have this parameter, and is it set to yes?:

 bjorn nemi:~$  grep . /sys/module/cdc_ncm/parameters/prefer_mbim
 Y

If so, then the problem may be solved by

 echo N >/sys/module/cdc_ncm/parameters/prefer_mbim

followed by unbinding the modem from cdc_mbim and rebinding it to
cdc_ncm.  Which should happen automatically if you "unplug" and replug
it (I know it's an internal module, but this might still be possible
using rfkill).

Or just unload the drivers and reload them to test:

 modprobe -r cdc_mbim
 modprobe cdc_ncm prefer_mbim=N


If this works, then you may want to add a config workaround until MM
support for MBIM is ready. Put something like this into a new
/etc/modprobe.d/avoid-mbim.conf file:

 options cdc_ncm prefer_mbim=N


(Note that you probably do want to remove this again when the MBIM
support is available, because that will enable MM to better manage your
modem).

> I can provide logs, if needed.

That would be good to confirm my wild guesses.  Preferably including
enough kernel logs to see which drivers are binding to the device.


Bjørn