From: "Shawn J. Goff" <shawn.goff@accelecon.com>
To: netdev <netdev@vger.kernel.org>
Subject: qmi-wwan bug
Date: Wed, 24 Oct 2012 14:50:04 -0400 [thread overview]
Message-ID: <5088385C.1090304@accelecon.com> (raw)
I've backported qmi-wwan to 2.6.39 (it's here:
https://bitbucket.org/accelecon/linux-at91/changesets), and it mostly
works, but I've come across a problem. The modem will sometimes stop
responding to any qmi data (but the AT commands on the TTY ports keep
working). This only happens when there is significant traffic flowing
through the device (downloading a large file) while at the same time, AT
commands are sent to one of the TTY ports (I first noticed with my own
modem query program, but I can reproduce it using microcom to send
"ATI\r" in a loop). I see this problem with different devices from
different manufacturers. I've only made it happen on my kernel - I tried
on 3.6.2, but it seems to not happen there. I've also tried using a
similar modem that uses a different driver (sierra-net) and that doesn't
have the same problem.
When it is in failure, if I try to ping an address, the system sends out
several an ARP requests but gets no response. To get the device to
respond again, I have to administratively set the wwan interface down,
then up, use libqmi to get the connection going again, then dhcp to get
an address.
I also have some USB traces of the failure and recovery process. I'm not
familiar with CDC or QMI, so it's not yet clear to me exactly what's
happening, but it looks like the modem just stops sending anything on
its QMI endpoint for no reason.
How might I dive further into the issue? So far, my next step is to look
into CDC and QMI and try to decypher the USB traces. If anyone is
interested, I can share a tcpdump or a USB trace.
--
Shawn J. Goff | Accelerated Concepts | Embedded Systems Engineer | 1-813-983-7501
next reply other threads:[~2012-10-24 18:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-24 18:50 Shawn J. Goff [this message]
2012-10-24 21:19 ` qmi-wwan bug Bjørn Mork
2012-10-24 22:28 ` Shawn J. Goff
2012-10-25 7:40 ` Bjørn Mork
2012-10-25 10:19 ` Shawn J. Goff
2012-10-25 10:36 ` Aleksander Morgado
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