HP lt4120 failing to make single-stack connections on LTE using MM

Bjørn Mork bjorn at mork.no
Thu Sep 6 08:46:12 UTC 2018

Aleksander Morgado <aleksander at aleksander.es> writes:

> Oh wait, this is a Intel based MBIM modem, right? If so, we need
> AT-based reset operations. I believe I still have the HPlt4120 around
> here, will try to implement that. Tracking it here:
> https://gitlab.freedesktop.org/mobile-broadband/ModemManager/issues/86

Don't know if we've discussed this before, but based on testing with the
EM7345 and looking at the Windows stuff, I believe it supports a vendor
MBIM service usable for reset:

UUID_FWUSVC =>  UNKNOWN (0ed374cb-f835-4474-bc11-3b3fd76f5641)
    DssPayload: 0x00000000
    MaxDssInstances:    0
    CidCount:   1
    CidList:    1
   CID_MODEM_REBOOT   <unknown> (1)

My notes are a bit sketchy as always, and the modem is stowed away, but
I believe that was the only CID of that service and that it only
supported SET requests.  With immediate modem reset as a result.


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