Re: Sierra USB 306 - GetSignalQuality() fails when connected: "Could not parse the +CIND response"

[Dan Williams <dcbw redhat com>]

On Mon, 2012-11-26 at 18:59 -0800, Kelsey Sigurdur wrote:
> On Mon, Nov 26, 2012 at 10:26 AM, Dan Williams <dcbw redhat com> wrote:
> > On Fri, 2012-11-23 at 17:33 -0800, Kelsey Sigurdur wrote:
> >> Hi folks,
> >>
> >> Newb here. As the subject says,  GetSignalQuality() is failing with
> >> the error "Could not parse the +CIND response" when connected to the
> >> network. When disconnected but enabled GetSignalQuality() properly
> >> returns a value.
> >>
> >> I'm just looking to find out if this is a issue with the hardware or
> >> perhaps a bug in ModemManager.
> >>
> >> I've scoured the archives as far back as January 2011 and the closest
> >> problem to mine that I've found so far is the following thread, which
> >> wasn't followed up on:
> >>
> >> "Re: how to get signal strength of EVDO modem"
> >> https://mail.gnome.org/archives/networkmanager-list/2011-January/msg00073.html
> >
> > So here's what's going on.
> >
> > 1) you don't appear to have the sierra_net driver on your system, or if
> > you do, it's not bound to the USB 306.  The USB 306 should expose a
> > network port as well as a few serial TTYs, and ModemManager should pick
> > that network port up.  The logs you posted indicate that the kernel
> > isn't binding sierra_net to the USB 306, so this appears to be a kernel
> > or modeswitch issue.
> >
> > 2) Because there's no network port, you only get one full-featured AT
> > command port, which is used for PPP while connected.  The other
> > AT-capable ports have limited AT command parsers which do not allow the
> > AT+CIND command, which is why you get that error.  However, there's a
> > bug in ModemManager where it should just report the signal quality
> > obtained by +CSQ instead of returning an error.
> >
> > So, I'd suggest finding out why sierra_net isn't getting used, but I'll
> > also fix the MM bug too.
> >
> > Dan
> >
> 
> Thanks Dan.
> 
> I do have the sierra_net driver on my system but you are correct that
> it's not getting bound to the device.
> 
> For now I'm guessing it's a kernel issue. Google, and my rudimentary
> understanding of C, suggests that the USB 306 is blacklisted in
> sierra.c but would work with a firmware version >= M3.0.
> Unfortunately,  the Sierra Wireless site offers only M2_0_11_10AP as
> the latest firmware for this device.

Ah, you're right.  My USB306 has firmware version 3, and I have no idea
where I got that firmware version, or even what firmware version it had
when I got it from Sierra.  I did a bunch of searching around to find
out if there was a firmware upgrade for the 306, but couldn't find one
beyond the version you have.

> See http://lwn.net/Articles/385096/ if you're interested in where I
> came across the blacklist info.
> 
> I'm off to investigate modeswitching. Thanks for the tips, I appreciate it.

So in light of this, I'll assume that the USB306 allows PPP on the
secondary APP ports.  This makes the APP1 port with the limited AT
parser the PPP/data port, so that we can continue to issue normal
commands on the main port, instead of the main port being used for PPP
and APP port rejecting most of what we want to do.

To test that out, do this:

mv /usr/sbin/modem-manager /
killall -TERM modem-manager
MM_SIERRA_APP1_PPP_OK=1 /modem-manager --debug

and then reconnect and see if the signal strength turns out OK.  I can't
recall if I tested PPP on the APP1 port with the USB306, but the above
commands will force that to occur.  If it works, I'll add a quirk for
the 306.

Dan