On Wed, Mar 05, 2025 at 10:02:15PM +0000, incansvl wrote: > Team, > > I am experiencing a problem on multiple versions of the 6.x kernel, where initialisation > of a motherboard usb hub device fails and causes a stream of errors. The performance of the > machine is badly affected. > > I would have considered this most likely a hardware fault except- > > 1) I am seeing the same issue on 2 machines of very different age and spec. The differences may not matter if they use similar hardware components. > 2) In each case the hub generating errors has no external devices connected to it, so > the error can't be caused by an external device that has failed. In fact on > "machine 2", having no devices plugged in seems to be a necessary condition for the > error to occur (see details below). > > I found the discussion of this patch, but I am not clear about this description- I suspect that patch has nothing to do with your problem. Have you tried applying (or reverting) it to see if that causes the problem to go away? > 4) On both machines the errors relate to a USB root hub that has NO DEVICES connected to it. > On "machine 2", having a powered USB3.0 hub (which has a number of downstream devices > connected) plugged in to one port on the hub is enough to suppress the errors, although > I note the that "bad" port number (hub 2 : port 3) is not enumerated (skipped?). > (tail of "dmesg -w") > [ 781.020436] usb usb2-port3: Cannot enable. Maybe the USB cable is bad? > [ 784.990637] usb usb2-port3: Cannot enable. Maybe the USB cable is bad? ... Please try collecting a usbmon trace for bus 2 showing the problem. Ideally the trace should show what happens from system boot-up, but there's no way to do that. Instead, you can do this (the first command below disables the bus, the second starts the usbmon trace, and the third re-enables the bus): echo 0 >/sys/bus/usb/devices/usb2/bConfigurationValue cat /sys/kernel/debug/usb/usbmon/2u >usbmon.txt & echo 1 >/sys/bus/usb/devices/usb2/bConfigurationValue Then after enough time has passed for the errors to show up, kill the "cat" process and post the resulting trace file. (Note: If your keyboard is attached to bus 2, you won't be able to use it to issue the second and third commands. You could use a network login, or put the commands into a shell file and run them that way.) In fact, you should do this twice: The second time, run it on machine 2 with the powered hub plugged in to suppress the errors. Alan Stern
