Quectel UC20: Correct way to get it up and running on embedded?

[Dan Williams]

On Tue, 2017-03-28 at 18:33 +0200, Bjørn Mork wrote:
> Einar Jón <tolvupostur at gmail.com> writes:
> > On 23 March 2017 at 02:42, Dan Williams <dcbw at redhat.com> wrote:
> > > 
> > > RE PolicyMismatch: we're not quite sure what that error
> > > represents;
> > > we've determined that in some cases it means IPv4 vs. IPv6
> > > mismatch and
> > > profiles in the modem, but that doesn't seem to always be the
> > > case.
> > 
> > I'm not sure what is causing it, but it's quite easy to reproduce
> > by
> > messing with the kernel module (e.g. reloading it):
> > $ sudo rmmod qmi_wwan
> > $ sudo modprobe qmi_wwan
> 
> My best guess is that you experience some mismatch between an
> auto-connected bearer and the bearer you try to connect.  But it's a
> wild guess.  Try messing with the preconfigured profiles, changing
> between IP, IPV6 and IPV4V6 contexts and see if you can prevent the
> issue that way.

Are the QMI "autoconnect" settings actually the EPS Default Bearer, or
are they different?  Maybe

qmicli --wds-set-autoconnect-settings=disabled

would do the trick, but I don't know for sure.

Dan

> 
> > I have a couple of other ways to reset the modem, but no easy ones:
> > 1)  The Quectel manual says that the command
> > AT+QRST=1,0
> > will reset the modem immediately, but I don't know how to send AT
> > commands to the modem.
> > There's no /dev/ttyUSB*, although the device is connected via USB:
> > $ mmcli -m 0 | grep devices
> >   System   |         device:
> > '/sys/devices/pci0000:00/0000:00:17.0/0000:01:00.0/0000:02:08.3/usb
> > 2/2-3'
> > 
> > 2) There's also a Control Signal Pin PERST# on the UC20 Mini PCIe
> > board:
> > - You can reset the module by driving the PERST# to a low level
> > voltage of more than 150ms and then release it.
> > Messing with the pins seems a bit drastic...
> > 
> > 3) Rebooting the linux machine also seems to work, but this kills
> > our uptime.
> 
> 
> You could try a USB reset.  There is a utility for that in the latest
> (yet unreleased) usbutils:
> https://github.com/gregkh/usbutils/blob/master/usbreset.c
> 
> This will reset the USB device controller, but not necessarily reboot
> the modem. So I am not sure it makes any difference in your
> case.  But
> worth trying if you haven't already.
> 
> 
> 
> Bjørn