[ltp] Re: Verifying Linux compatibiliy for the LTE modems in the 2nd gen X1 Carbon

[Bjørn Mork]

Peter FP Zhang <zhangfp1@lenovo.com> writes:

> Hello Bjørn, 
>
> Do you have any good ideas about the following issue? :)
>
> Bug 729860 
> Huawei ME906C(12d1:15c0) 4G LTE not working.
> https://bugzilla.gnome.org/show_bug.cgi?id=729860


There isn't anything looking like a bug in that report.  The
ModemManager log shows a normal modem discovery, and the result is
summarized in this part of the mmcli output:
		
  -------------------------
  System   |         device: '/sys/devices/pci0000:00/0000:00:14.0/usb2/2-4'
           |        drivers: 'cdc_ether, option1'
           |         plugin: 'Huawei'
           |   primary port: 'ttyUSB0'
           |          ports: 'ttyUSB0 (at), ttyUSB1 (qcdm), ttyUSB2 (at), ttyUSB3 (at), usb0 (net)'
  -------------------------


mbimcli doesn't work here because there are no MBIM ports.  The current
device configuration shows 4 serial ports (where 3 are AT command ports
and the last is a Qualcomm Device Management port) and one CDC ECM port.

I assume the ECM port can be managed using the normal Huawei vendor
specific AT commands (AT^NDISDUP etc) on one of the serial ports. The MM
Huawei plugin managing this modem will know how to do that, and as you
can see it will use 'ttyUSB0' for this.

So this should just work. Reading between the lines I guess there is
something later in the chain that is failing (nm-applnm-appletet) but I don't see
any information related to this.

It also looks like the user expects this modem to support MBIM.  And I
guess it does?  But like most modern Huawei devices it probably has a
number of different identities. The one we see here looks like a
"legacy" one, intended to support older systems like Windows7 etc.
Being a Qualcomm based device, I wouldn't be suprised if one of the
identities supported QMI too.

We'd have to see the dmesg output and usb_modeswitch log to understand
how it ended up with this identity.  MM is not involved in that part of
the device setup.  It can only probe the end result, and it has done so
successfully AFAICS.



Bjørn






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