Sierra EM7455 takes 3+ minutes to connect after suspend/resume

[Aleksander Morgado]

>
> Having a similar, but different issue with another Sierra EM7455 in
> combination with Fedora 27 with ModemManager 1.6.10 and a thinkpad x270.
>
> Running ModemManager in console producer the following attached output.
> Laptop is put into sleep mode at 1510810951.  After resuming it takes about
> 55 seconds on this try to appear in network manager and ready to connect.
>
> From an initial glance at this it seems that it spends a lot of time probing
> around and I see various 'serial command timed out'. Is this something that
> I can improve with various udev configurations?  Possibly there is a way to
> have MM prefer the last known working configuration so it doesnt have to try
> all the various plugins again?
>

It probably spends time reprobing the TTYs, yes. If you know which
ones are not responding (e.g. maybe GPS data port) you could blacklist
them with ID_MM_PORT_IGNORE rules.

-- 
Aleksander
https://aleksander.es