Comment 4 for bug 1912670

Thanks. Here are the results of your suggestions, plus some other things I tried:

1. 'tlp' was not installed.

2. I installed 'powertop' and checked its 'Tunables' section. There were 6 entries for "Autosuspend for USB device xHCI Host Controller" all set to 'Good' - I changed these to 'Bad'. The problem still occurred.

3. Further diagnostics eventually led to my trying the following:
    * added "usbcore.autosuspend=-1" to the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub
    * ran: sudo update-grub
    * rebooted
    * cat /sys/module/usbcore/parameters/autosuspend
        [shows -1 as expected]
    * cat /sys/bus/usb/devices/usb[1-6]/power/autosuspend_delay_ms
        [now shows -1000 - (was previously 0) ]
but the problem still occurs.

4. Repeated the above GRUB change with the parameter 'autosuspend_delay_ms' rather than 'autosuspend'.
    * ls /sys/module/usbcore/parameters
        [shows an 'autosuspend' parameter but not an 'autosuspend_delay_ms' parameter]
    * sudo modinfo usbcore
        [shows: parm: autosuspend:default autosuspend delay (int)]
    * cat /sys/bus/usb/devices/usb[1-6]/power/autosuspend_delay_ms
        [now shows 0]
but the problem still occurs.

In all cases I still get the same five 'device removed' messages in /var/log/Xorg.0.log as originally reported, and the mouse and keyboard are unresponsive after a few minutes idle time.