Greg's House of Treats

USB Disconnects for KVM

I'm having a problem with my new KVM on debian. When I switch away from the linux box for a while (~10 mins?), the USB connection doesn't restore. In /var/log/messages, I should get something like this:


// KVM switch away from linux
Apr 7 18:12:55 fantasy kernel: [ 876.298235] usb 1-4.2: USB disconnect, address 7

// KVM switch back to linux
Apr 7 18:14:37 fantasy kernel: [ 977.868135] usb 1-4.2: new low speed USB device using ehci_hcd and address 8
Apr 7 18:14:37 fantasy kernel: [ 977.964462] usb 1-4.2: configuration #1 chosen from 1 choice
Apr 7 18:14:37 fantasy kernel: [ 977.973508] input: HID 1267:0103 as /class/input/input13
Apr 7 18:14:37 fantasy kernel: [ 978.000079] input,hidraw2: USB HID v1.10 Keyboard [HID 1267:0103] on usb-0000:00:1d.7-4.2
Apr 7 18:14:37 fantasy kernel: [ 978.003992] input: HID 1267:0103 as /class/input/input14
Apr 7 18:14:37 fantasy kernel: [ 978.032767] input,hidraw3: USB HID v1.10 Device [HID 1267:0103] on usb-0000:00:1d.7-4.2
Apr 7 18:14:37 fantasy kernel: [ 978.032871] usb 1-4.2: New USB device found, idVendor=1267, idProduct=0103
Apr 7 18:14:37 fantasy kernel: [ 978.032875] usb 1-4.2: New USB device strings: Mfr=0, Product=0, SerialNumber=0


But sometimes I switch away from linux, and it never comes back. I tested a live CD which doesn't exhibit this problem. But debian does.

Here is my first try at a workaround, as suggested here at http://www.mail-archive.com/linux-usb-users@lists.sourceforge.net/msg16653.html

echo -n 1-4:1.0 >/sys/bus/usb/drivers/hub/unbind
echo -n 1-4:1.0 >/sys/bus/usb/drivers/hub/bind

The above sort of works. The first time you run it, the usb disconnects and then reconnects as USB 1.x. But the usb freezes again, and unbind/bind fails.

Next I try the following, as suggested here at http://ubuntuforums.org/showthread.php?t=234095

sudo modprobe -r ehci_hcd

This works.