Random input/output errors with /dev/cdc-wdm* in kernel 4.9.7
bjorn at mork.no
Thu Feb 2 12:57:23 UTC 2017
Kasper Holtze <kasper at holtze.dk> writes:
> After upgrading Linux from 4.4.8 to 4.9.7, I'm seeing some strange
> issues connecting to my modems. The modem is Sierra MC7304, in QMI
> As it happened after upgrading the kernel, I'm not sure if it is
> directly related to libqmi.. Could be the qmi_wwan driver?
> I see the issues with both qmicli and my custom software.
> libqmi is version 1.16.2.
> Usually it works fine when the system is first booted, or the modems
> are reset. After a while, I'm getting i/o errors reading from
> Sometimes it just hangs, most of the times I get this message:
> Qmi-WARNING **: Error reading from istream: Error reading from file
> descriptor: Input/output error
> I have enabled debugging in debugfs, and get this in the syslog:
> [ 5664.134111] wdm_open: qmi_wwan 1-1.3:1.8: draining queued data
> [ 5664.134778] wdm_in_callback: qmi_wwan 1-1.3:1.8: nonzero urb status
> received: -EPIPE
> [ 5664.136365] wdm_int_callback: qmi_wwan 1-1.3:1.8:
> NOTIFY_RESPONSE_AVAILABLE received: index 8 len 0
> [ 5664.136390] wdm_int_callback: qmi_wwan 1-1.3:1.8: submit response URB 0
> [ 5664.136903] wdm_in_callback: qmi_wwan 1-1.3:1.8: nonzero urb status
> received: -EPIPE
> [ 5664.137551] wdm_release: qmi_wwan 1-1.3:1.8: wdm_release: cleanup
Not good. This is a mess, and I can only admit that I have completely
lost track of how it is supposed to work....
I wonder if you are able to test a cdc-wdm/qmi-wwan driver with these
two commits reverted one-by-one? :
c1da59dad0eb ("cdc-wdm: Clear read pipeline in case of error")
833415a3e781 ("cdc-wdm: fix "out-of-sync" due to missing notifications")
That's sort of a quick "bisect". A full bisect would achieve the same,
but I don't think it will provide more info. I am pretty sure the
problem is caused by one (or both) of those two commits which both went
Let me know if you need more details on how to do this.
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