Re: [linux-usb-devel] ThinkPad T41 - Strange USB 2.0 behaviour

[Alan Stern]

On Sun, 10 Jun 2007, Robert de Rooy wrote:

> Alan Stern wrote:
> > Unfortunately you posted the system log file instead of the dmesg log, 
> > and your syslogd was configured not to retain debug-level messages.
> >   
> Ok, I did not realize my syslog was filtering the debug-level messages, 
> here is the output from dmesg

> *** plugging device (leaving it in slightly to long, hence the long 
> log); removing the device; rmmod ehci-hcd; plug back in
> usb usb4: usb resume
> usb usb4: finish resume
> hub 4-0:1.0: hub_resume
> ehci_hcd 0000:00:1d.7: resume root hub
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0000
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001803 POWER sig=j CSC 
> CONNECT
> hub 4-0:1.0: port 4, status 0501, change 0001, 480 Mb/s
> hub 4-0:1.0: debounce: port 4: total 100ms stable 100ms status 0x501
> ehci_hcd 0000:00:1d.7: port 4 high speed
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001005 POWER sig=se0 PE 
> CONNECT
> usb 4-4: new high speed USB device using ehci_hcd and address 2
> ehci_hcd 0000:00:1d.7: devpath 4 ep0in 3strikes
> ehci_hcd 0000:00:1d.7: devpath 4 ep0in 3strikes
> ehci_hcd 0000:00:1d.7: devpath 4 ep0in 3strikes
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001002 POWER sig=se0 CSC
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0010
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0010
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001803 POWER sig=j CSC 
> CONNECT
> hub 4-0:1.0: port 4, status 0501, change 0001, 480 Mb/s
> hub 4-0:1.0: debounce: port 4: total 100ms stable 100ms status 0x501
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001002 POWER sig=se0 CSC
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0010
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0010
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001803 POWER sig=j CSC 
> CONNECT
> hub 4-0:1.0: port 4, status 0501, change 0001, 480 Mb/s
> hub 4-0:1.0: debounce: port 4: total 100ms stable 100ms status 0x501
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001002 POWER sig=se0 CSC
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0010
> hub 4-0:1.0: state 7 ports 6 chg 0000 evt 0010
> ehci_hcd 0000:00:1d.7: GetStatus port 4 status 001803 POWER sig=j CSC 
> CONNECT

Okay.  It's clear that you've got a hardware problem of some sort.  
Hard to say what it is, but evidently the EHCI controller thinks that 
the device is repeatedly being unplugged and replugged.

Anyway, this isn't a problem of recognizing that a single device is
having problems.  In fact the computer has no way of knowing that a
single device is involved; all it knows is that _something_ gets
plugged into the port and then removed.  There's no way to tell if it's 
the same _something_ from one iteration to the next.

You can manually force the port to run at full speed instead of high 
speed as follows:

	echo '4' >/sys/class/usb_host/usb_host4/companion

The "companion" attribute file contains a list of ports which are 
permanently set to be handled by the EHCI's companion controller.  To 
return to high-speed operation, use '-4' instead of '4' above.  This 
might or might not solve your problem -- the hardware bug might cause 
the port to return automatically to high-speed regardless.

Let me know what happens.

Alan Stern

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