MC7455 sporadically wrong primary port

[Aleksander Morgado]

On Tue, Jul 4, 2017 at 5:37 PM, Karoly Pados <kp at tec4data.at> wrote:
> 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.

ModemManager will try each time to find which is the "best" port to
control the modem. If the port probing of the cdc-wdm QMI ports goes
ok, it will usually just pick the QMI port for control. Whether it's
cdc-wdm0 or cdc-wdm1 it *shouldn't* matter, but there are usually
differences; one of those may be associated to a wwan that is
configured in "raw-ip" and the other one to a wwan configured in
"802.3".  The way ModemManager asks to get those interfaces configured
by NetworkManager will be different (if in raw-ip mode it will request
static IP config, if in 802.3 it will request DHCP). But we don't know
this until you get some debug logs, or at least the output of "mmcli
-b 0" (show bearer #0 info) when the modem gets connected in both
success and failing cases. We know the MC7455 didn't support switching
from raw-ip to 802.3; but maybe it does initially configure the
secondary wwan in 802.3 mode and we need to force it to raw-ip to work
correctly, or something.

Regarding the tty as primary port; that will only happen when the
"probing" of the QMI ports fail. We really would need debug logs to
analyze that. But first, I see you're using an MM 1.6.2; I would
suggest you try with the latest stable ModemManager 1.6.8 or even
better with ModemManager git master, just to rule out issues  that may
already have been solved.

-- 
Aleksander
https://aleksander.es