How to resume the USB device after selective suspend configuration in Ubuntu host

Question

I have Linux based development board on which DWC3 USB controller driver is present. I have implemented Link Power Management(L2 state) in the usb driver. Ubuntu is the host which on which my development board is connected via USB.

I need to perform regression testing of USB suspend-resume by using shell script. I have managed to write some portion of it,

**usb suspend-resume.sh**

path=1-10
echo auto > /sys/bus/usb/drivers/usb/$path/power/control 
echo 10 > /sys/bus/usb/drivers/usb/$path/power/autosuspend

sleep 10

iteration="10"
count="0"

while [ $count -lt $iteration ]
do
    rs=$(cat /sys/bus/usb/drivers/usb/$path/power/runtime_status)

    if [ "$rs" = "suspended" ]  
    then    
        echo usb is suspended
        sleep 5     
        count=$((count+1))
    fi
done

Devices on Ubuntu 14.04: /dev/ttyACM0 /dev/ttyACM1 /dev/ttyACM2 /dev/ttyACM3

The above script could perform only suspend(every 10s) but i'm not able to proceed how to resume the device.

Answer 1

To resume the suspended device

echo on > /sys/bus/usb/devices/$path/power/control

This should activate the suspended device. You can check for the state of the device using

cat /sys/bus/usb/devices/$path/power/runtime_status