After modem reset is USB connections not re-added

[Aleksander Morgado]

Hey Karsten!
>
> openWrt version is
>        OpenWrt 19.07.2, r10947-65030d81f3
>
> After power on is sysfspath OK and I can access modem via mmcli.
> I reset modem by use the command mmcli -m <sysfspath>   --reset
> According to logread -e hotplug is USB connections removed which is OK.
> I expect the USB connections to be re-established after a while.
> But nothing is re-established according to the following commands:
>      1.       logread -e hotplug
>      2.       dmesg | grep -i usb
>      3.       ls -l  /dev
>      4.       ls -l <sysfspath
>
> As I read the log ModemManager  remove the USB connection at reset but do not add USB connections again
>

That's weird.

> Is  ModemManager responsible for re-establish  USB connection  ?

No, not at all. After a --reset, MM asks the modem to reset itself.
The modem should re-appear in the USB bus by itself.

> Do anyone have a method to trig   re-establish of USB connection ?

Could it be that the RM500 requires a new power-up sequence via GPIO
for some reason? It would be a bit weird to require that after a
--reset operation, but who knows. This is a question to ask to Quectel
I guess.

> If Habanero  evaluation board is power up WITHOUT connection to Quectell RMU500  modem  evaluation  board there is of cause no USB connections.
> But I expect the connection to pop up at plug in the USB cable which connect the two boards.  But the situation is exactly the same as after reset of modem.
> Who is responsible for continuously try to establish  USB connection in case the connections are down. ?

If I'm not mistaken, the USB device should present itself in the bus
and then the USB host would take care of managing all the
communication to enumerate and bring up the device. If you're using an
external eval board for the module, it may very well be that the
module requires some kind of initialization to be done in the board
itself (e.g. manually pressing the reset button or something like
that). I would definitely talk to Quectel about this and ask them what
they think. Also, the eval board documentation should help w.r.t.
module bootup sequence.

Cheers!

-- 
Aleksander