EM7565 failing if host reboots whithout power cycling the modem

[John Marrett]

Bjørn,

But what can be done about that?  From my point of view, fixing the
> issue in the modem firmware is out of the question. The modem is running
> SWI9X50C_01.14.13.00, which the latest available.
>

You should either open a case with the modem manufacturer if you have some
kind of support agreement. If you don't then you could ask about it on the
sierra wireless forums ( https://forum.sierrawireless.com/ ). This problem
is likely to affect other people and you have very detailed and clean
information about the problem. Sierra can raise it to the modem
manufacturer.

Have you tried unloading xhci_pci before rebooting the system? This might
help?


> We need a woraround for the host system.  But what?  Since I have adb
> access, I can obviously just reboot the modem.  Which works.  But what
> about the "normal" modem configuration?  Figure out a way to cut USB
> port power?  I guess this is possible on that platform, although I don't
> think it's implemented.  It's not a very generic solution, though.  But
> maybe this isn't a very generic problem?


Unfortunately this is a very normal problem :) I manage a lot of modems of
different types and models and also do some consulting in this space. On
every platform and with a variety of modems it's always been necessary to
implement watchdog scripts that reboot the modem when it fails to stop
responsing. I've always found a GPIO to cut power to the modem in a worst
case. I don't see a named usb gpio in your router's OpenWrt configuration
but I expect that there must be something, even if it isn't named. I'm
happy to help you explore /sys/class/gpio if you need a hand.


> Maybe it's just this exact
> combo of host controller, device and continous power to the port during
> reboot (which I'm very much in favour of in general)?
>
> Have anyone else noticed similar problems with the EM7565?  Or any other
> Qualcomm MDM9x50 device?  I assume this bug isn't really Sierra Wireless
> specific, but rather something they got from Qualcomm.
>

Yes, but Sierra will raise it to Qualcomm.


> You'll obviously not see this problem if your host system cuts power to
> the USB port on reboots.  Which unfortunately often is the case.
>

I haven't seen this kind of behaviour before. USB devices have always been
rebooted with the host on other embedded routers.

-JohnF
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