[OpenWrt-Devel] ramips/mt7621 after 5.4 switch

Bjørn Mork bjorn at mork.no
Tue Apr 7 10:33:56 EDT 2020

Andre Valentin <avalentin at marcant.net> writes:

> 3) Problems with QMI Interfaces
> QMI is used for mobile phones and interact with the qmi_wwan driver in the kernel. I had transmit issues,
> switched the driver back to the 4.14 while still on 5.4. But the same problem happens again.
> Under 4.14 this was not a problem. So it seems 5.4 or the SOC patches somehow are the root cause.
> Here's the kernel message:
> [ 4199.444191] ------------[ cut here ]------------
> [ 4199.453534] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:447 dev_watchdog+0x2f8/0x300
> [ 4199.470074] NETDEV WATCHDOG: wwan0 (qmi_wwan): transmit queue 0 timed out

And this is not just an occasional timeout?  The driver hangs completely

I don't think there were many qmi_wwan changes between v4.14 and v5.4,
except for device additions and some fixes which mostly have been
backported to v4.14-stable. But maybe this is related to your specific
modem?  Do you have a device ID for that?

Do we know that USB is working on v5.4 BTW?  The MT7621 device I am
using doesn't have any USB ports, so I can't check that myself.

Is your modem connected by USB3 or USB2?  Any of

 lsusb -v
 cat /sys/kernel/debug/usb/devices
 grep . /sys/bus/usb/devices/*/version

will tell.  You'll have to match up the latter with the device if you
have more than one USB device connected.


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