Kernel message spew on reboot - Quectel EG25-G

[Bruce Johnson]

I never saw a response on this question, but I finally figured out -- 
with some assistance from a Quectel engineer -- that the error is a 
kernel error related to USB communication with the modem as everything 
is being shut down for the reboot, and that ModemManager has no direct 
link to the issue. I've made a tiny kernel patch that seems to resolve 
the problem and have sent it to Quectel for consideration.

Bruce Johnson
Chantilly, Virginia
USA

On 26/08/2024 11:52, Bruce Johnson wrote:
> I am getting a kernel message spew on the console whenever I reboot 
> one of my boxes that's equipped with a Quectel EG25-G modem:
>
>> option1 ttyUSB0: usb_wwan_write: submit urb 0 failed: -19
>
> When this happens, the reboot either does not complete or takes so 
> long that it is unacceptable. It happens after the system has closed 
> systemd-journald, so I haven't yet been able to find any additional 
> information that might help.
>
> If I stop ModemManager for a little while before issuing the reboot, 
> this doesn't happen. I've tried juggling the shutdown order and timing 
> of the relevant systemd services but haven't yet found a way to put in 
> sufficient delay for a reboot to occur reliably.
>
> My team is currently upgrading our project from Yocto's Dunfell branch 
> to their Scarthgap branch. This takes us from Linux kernel 5.4.34 to 
> 6.6.23, and from ModemManager 1.18.4 to 1.22. Everything worked great 
> in the old setup.
>
> I'm not well acquainted with either body of source code (ModemManager 
> or Linux kernel). Can anyone advise me on how I might be able to 
> figure this out?
>