On Wed, 29 Nov 2006, José Alfredo Cañizo Rincón wrote:

> On my system, kernel 2.6.18.3 sends repeated messages which keep
> 
> appearing on every console and in the system logs at a rate of four
> 
> per second or so since boot.
> 
> 
> 
> On the console:
> 
> 
> 
> hub 1-0:1.0: over-current change on port 2
> 
> 
> 
> In system logs:
> 
> 
> 
> Nov 28 02:36:58 mundolimite kernel: hub 1-0:1.0: trying to enable port power 
> on non-switchable hub
> 
> Nov 28 02:36:58 mundolimite kernel: hub 1-0:1.0: state 7 ports 2 chg 0000 evt 
> 0004
> 
> Nov 28 02:36:58 mundolimite kernel: uhci_hcd 0000:00:07.2: port 2 portsc 
> 0980,00
> 
> Nov 28 02:36:58 mundolimite kernel: hub 1-0:1.0: over-current change on port 2
> 
> 
> 
> The problem disappears by unloading the module uhci_hcd. However, if
> 
> the module remains loaded, the usb port seems to work perfectly,
> 
> though these annoying messages keep appearing and filling the system
> 
> log. The problem does not happen with any of the 2.4 kernels I've
> 
> tried.

That's because the 2.4 driver doesn't report overcurrent conditions.  I 
think.

> An interesting thing is that my system only has one usb port. Here is the
> 
> output of lspci -v related to the usb controller:

The computer may have only one physical port, but the UHCI controller has 
two sets of I/O lines.  Apparently the unused set has been wired in such a 
way that the overcurrent input constantly changes state.

> 00:07.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 
> Controller (rev 0a) (prog-if 00 [UHCI])
> 
>         Subsystem: VIA Technologies, Inc. (Wrong ID) USB Controller
> 
>         Flags: medium devsel, IRQ 11
> 
>         I/O ports at 3000 [disabled] [size=32]
> 
>         Capabilities: [80] Power Management version 2
> 
> 
> 
> The computer is a Chembook laptop with an AMD-K6-III processor
> 
> (about four years old, manufactured by ChemUSA). The kernel was
> 
> compiled with CONFIG_USB_DEBUG=y. It is
> 
> $ uname -a
> 
> Linux mundolimite 2.6.18.3 #1 Mon Nov 27 22:51:30 CET 2006 i586 GNU/Linux
> 
> 
> 
> After looking around it seems that a similar error happens in Compaq
> 
> Armada laptops; see
> 
> https://launchpad.net/distros/ubuntu/+source/linux-source-2.6.15/+bug/8772
> 
> http://lists.linuxcoding.com/rhl/2004/msg42957.html
> 
> 
> 
> Note that the hardware reported by lspci in the first of these pages
> 
> is similar to mine (my complete lspci -v output is below at the end of
> 
> the message). There, it was finally considered to be a hardware
> 
> problem, which might be correct, but on my system usb works well. At
> 
> least there must be a way to stop them from constantly filling the
> 
> system log. Comments in uhci_hcd.c say some features are disabled for
> 
> certain faulty controllers; maybe disabling this over-current warning
> 
> for this particular hardware is worth it?

There's nothing to indicate the controller is faulty; more likely the
wiring on the motherboard is.  Furthermore, that warning message isn't
produced by uhci-hcd; it's produced by the hub driver (you'll find it in
drivers/usb/core/hub.c).

> Any other idea on how to fix this?

There are a few possibilities.  For example, we could add a sysfs 
attribute file listing ports which should not be monitored for 
an overcurrent condition.

Alan Stern


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