MC7455 sporadically wrong primary port

[Karoly Pados]

Hi,

These ports all belong to the modem, it is a Sierra Wireless MC7455. "mmcli -m 0" says:

# mmcli -m 0

/org/freedesktop/ModemManager1/Modem/0 (device id 'be462cac113ea58f1817a2434babb491f9fe33f5')
  -------------------------
  Hardware |   manufacturer: 'Sierra Wireless, Incorporated'
           |          model: 'MC7455'
           |       revision: 'SWI9X30C_02.08.02.00 r5428 CARMD-EV-FRMWR2 2016/01/06 20:38:53'
           |      supported: 'gsm-umts
           |                  lte
           |                  gsm-umts, lte'
           |        current: 'gsm-umts, lte'
           |   equipment id: '359072060797244'
  -------------------------
  System   |         device: '/sys/devices/platform/soc at 01c00000/1c14000.usb/usb1/1-1/1-1.3'
           |        drivers: 'qmi_wwan, qcserial'
           |         plugin: 'Sierra'
           |   primary port: 'cdc-wdm0'
           |          ports: 'ttyUSB0 (qcdm), ttyUSB2 (at), cdc-wdm0 (qmi), wwan0 (net), wwan1 (net), cdc-wdm1 (qmi)'
  -------------------------
 (cut)

Running with kernel 4.9.35 and ModemManager 1.6.2.

As you can see the modem has multiple ports. The modem is the only USB device in the whole system (except for the on-board USB wifi adapter, which is non-removable). The phenomenon I'm seeing is that the "primary port" above is often something else than cdc-wdm0, sometimes even a ttyUSBX, and in these cases the modem is unusable for data. The only workaround I have is to keep resetting the modem until the correct primary port is picked.


Karoly

___________________________________________________________________

July 4, 2017 4:55 PM, "Carlo Lobrano" <c.lobrano at gmail.com> wrote:

> Hi Karoly,
> 
> which modem are you using?
> 
> cdc-wdmX and tty ports are used for totally different communication protocols. Like, if you're
> modem supports QMI or MBIM, it's ok to use cdc-wdmX, otherwise is ok to use tty. Also consider that
> is up to the kernel to assign the number at the end of cdc-wdmX and that number depends on which
> other hardware is connected to USBs.
> i.e. when I have my usb earphones connected, the kernel assigns cdc-wdm1 to the modem instead of
> cdc-wdm0.
> 
> Carlo
> On 4 July 2017 at 15:36, Karoly Pados <kp at tec4data.at> wrote:
> 
>> Hello,
>> 
>> Sometimes MM picks the wrong primary port. What I observed is that everything works if it picks
>> cdc-wdm0. But pretty often it picks cdc-wdm1, in which case NetworkManager is unable to establish a
>> data connection. Sometimes, much more rarely, it even picks ttyUSB0, and NM is then also unable to
>> do anything useful with the modem.
>> 
>> Now I'm not 100% sure that this is the cause for our problems, so my first question: Is it
>> plausible at all that anything other than cdc-wdm0 as a primary port is a problem?
>> 
>> If so:
>> - What can I provide to help solve this in code?
>> - Is there a way around it? (for example, a way to force MM to pick a specific port as primary?)
>> 
>> Thank you,
>> Karoly
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>> ModemManager-devel at lists.freedesktop.org
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