Modem not resetting.

[Dan Williams]

On Wed, 2020-04-29 at 07:22 +0200, Aleksander Morgado wrote:
> Hey,
> 
> > Hi, I see an issue when resetting modems, both with Telit and
> > Sierra. It happens quite rarely but renders the modem unusable. I
> > tell the modem to go offline and then to reset, most of the time
> > this works, it's a standard thing. Occasionally it will say that it
> > is a success but never actually reload, no matter how many times
> > you issue the commands after this the modem won't reset, and it
> > also can not come back online (invalid transition I assume). Here
> > is the verbose output if that helps in any way, any test you thinkI
> > can run while I have a modem in this state? (Telit LNM960A18)
> > 
> > 
> > I’ve run into this before with MDM 9207 modems from Telit and
> > Quectel, but only when the AT&T MBN (carrier profile) is activated.
> > Other carriers profiles did not exhibit this behavior.
> > 
> > I worked around the problem by skipping the “offline" mode step and
> > just sending a dms_set_operating_mode message with
> > QMI_DMS_OPERATING_MODE_RESET. See an implementation here:
> > 
> > https://github.com/temperednetworks/ModemManager/blob/752027d19f77e65b1d4568de49cf2599c49d4e9e/plugins/quectel/mm-broadband-modem-qmi-quectel.c#L198
> > 
> > I’m hesitant to upstream this because I know that some older
> > qualcomm chipsets return InvalidTransition when setting the
> > operating mode to QMI_DMS_OPERATING_MODE_RESET without first
> > setting it to QMI_DMS_OPERATING_MODE_OFFLINE.
> > 
> 
> If that is the case, we could always try RESET first, and if we get
> InvalidTransition, fallback to OFFLINE+RESET. That wouldn't harm I
> think.

That's what I was thinking too.

Dan