MC7455 can't transmit TCP data

[Dan Williams]

On Wed, 2016-10-26 at 16:51 +0800, dailijin wrote:
> 
> Hi All,
> 
> 
> I am testing MC7455 on Linux based on kernel 3.8, I have patched
> usbnet and qmi_wwan driver, the MC7455 modem can get  connected.
> But can't transmit TCP data. The modem information as below.
> ATI
> Manufacturer: Sierra Wireless, Incorporated
> Model: MC7455
> Revision: SWI9X30C_02.05.07.00 r5154 CARMD-EV-FRMWR2 2015/12/04
> 22:23:15
> MEID: A00000670DEA2A
> ESN: 12807659625, 8074E069
> IMEI: 359072060229115
> IMEI SV:  3
> FSN: LQ631307870110
> +GCAP: +CGSM
> OK
> 
> 
> Is there anyone encounter this issue?

This is likely a raw-ip versus 802-3 issue, the patches for which
landed way, way after 3.8.  Have you patched the qmi_wwan driver in
your kernel with recent improvements, or is it a vanilla 3.8 qmi_wwan?

In short: many new QMI devices no longer support "ethernet" mode, but
use raw-ip that skips the pointless ethernet framing.  There are kernel
enhancements required to make that work, and they landed long after
3.8.

Dan

> 
> Thanks
> 
> 
> 
> 
> --
> 
> Best Regards,
> Dai,Lijin
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