Quectel EG25 modem USB resets during the suspend/resume

When this happens you will see following in dmesg, which results in,

dmesg log

[  259.310589] usb 2-1: USB disconnect, device number 2                                                                                                                                                                                                                                                                      
[  259.311459] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0                                                                                                                                                                                                                                   
[  259.311601] option 2-1:1.0: device disconnected                                                                                                                                                                                                                                                                           
[  259.312742] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1                                                                    
[  259.312921] option 2-1:1.1: device disconnected                       
[  259.330856] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2                                                                    
[  259.331038] option 2-1:1.2: device disconnected                       
[  259.332192] option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3                                                                    
[  259.332339] option 2-1:1.3: device disconnected
[  259.332737] qmi_wwan 2-1:1.4 wwan0: unregister 'qmi_wwan' usb-1c1b000.usb-1, WWAN/QMI device                                                               
[  259.650482] usb 2-1: new high-speed USB device number 3 using ehci-platform
[  259.827872] option 2-1:1.0: GSM modem (1-port) converter detected   
[  259.828702] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB0
[  259.829439] option 2-1:1.1: GSM modem (1-port) converter detected  
[  259.831390] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB1
[  259.832184] option 2-1:1.2: GSM modem (1-port) converter detected
[  259.834117] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB2
[  259.836198] option 2-1:1.3: GSM modem (1-port) converter detected          
[  259.836901] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB3
[  259.840082] qmi_wwan 2-1:1.4: cdc-wdm0: USB WDM device                                                                                                     
[  259.841732] qmi_wwan 2-1:1.4 wwan0: register 'qmi_wwan' at usb-1c1b000.usb-1, WWAN/QMI device, a2:a6:1b:55:6c:b6

This causes ofono to "forget" state of the modem and reinitialize whole thing.

How to provide a verbose logs

• If you are on Manjaro Plasma Mobile image, install the custom kernel with dynamic_debug enabled from here
• Enable the dynamic debug for usb subsystem using following commands as root,

cd /sys/kernel/debug/dynamic_debug
echo 'file drivers/usb/* +p' > control
echo 'file drivers/usb/serial/usb_wwan.c -p' > control
echo 'file drivers/usb/serial/usb-serial.c -p' > control

• Try to reproduce this, and once you have reproduced it, pipe dmesg to some file and attach it here

• Since this prints lot of output in dmesg, if after some period you notice that bug is not happening, you can keep clearing dmesg buffer using sudo dmesg --clear periodically to reduce the amount of log messages.

• If you are not using Manjaro, you can enable CONFIG_DYNAMIC_DEBUG and CONFIG_DYNAMIC_DEBUG_CORE options in kernel