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I have a webcam, a mouse, and a wifi adapter all plugged into the same USB bus at the back of my computer. When I run a program to utilize the webcam, both the webcam and wifi adapter stop working and do not show up on my computer until I restart it. The moment I run a program to use the webcam, the following is logged to /var/log/kern.log:

Mar 26 23:10:13 doug-kubuntu kernel: [  121.025527] ehci_hcd 0000:00:12.2: force halt; handshake ffffc9000064a824 00004000 00000000 -> -110
Mar 26 23:10:13 doug-kubuntu kernel: [  121.025530] ehci_hcd 0000:00:12.2: HC died; cleaning up
Mar 26 23:10:13 doug-kubuntu kernel: [  121.025540] cannot submit urb 1, error -19: no device
Mar 26 23:10:13 doug-kubuntu kernel: [  121.025570] usb 1-2: USB disconnect, device number 3
Mar 26 23:10:13 doug-kubuntu kernel: [  121.025900] wlan0: deauthenticating from e0:91:f5:ab:2a:f3 by local choice (reason=3)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.136722] ath: phy0: Chip reset failed
Mar 26 23:10:13 doug-kubuntu kernel: [  121.136731] ath: phy0: Unable to reset channel (2462 Mhz) reset status -22
Mar 26 23:10:13 doug-kubuntu kernel: [  121.136761] ath: phy0: Unable to set channel
Mar 26 23:10:13 doug-kubuntu kernel: [  121.238761] ath: phy0: Chip reset failed
Mar 26 23:10:13 doug-kubuntu kernel: [  121.238771] ath: phy0: Unable to reset hardware; reset status -22 (freq 2462 MHz)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.251867] ath: phy0: Failed to wakeup in 500us
Mar 26 23:10:13 doug-kubuntu kernel: [  121.261871] ath: phy0: Failed to wakeup in 500us
Mar 26 23:10:13 doug-kubuntu kernel: [  121.261876] cfg80211: All devices are disconnected, going to restore regulatory settings
Mar 26 23:10:13 doug-kubuntu kernel: [  121.261878] cfg80211: Restoring regulatory settings                                                     
Mar 26 23:10:13 doug-kubuntu kernel: [  121.261880] cfg80211: Calling CRDA to update world regulatory domain                                    
Mar 26 23:10:13 doug-kubuntu kernel: [  121.275777] ath: phy0: Failed to wakeup in 500us                                                        
Mar 26 23:10:13 doug-kubuntu kernel: [  121.285766] ath: phy0: Failed to wakeup in 500us                                                          
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302587] cfg80211: Updating information on frequency 2412 MHz for a 20 MHz width channel with regulatory rule:                                                                                                                                               
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302598] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                         
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302604] cfg80211: Updating information on frequency 2417 MHz for a 20 MHz width channel with regulatory rule:                                                                                                                                                
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302609] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                          
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302613] cfg80211: Updating information on frequency 2422 MHz for a 20 MHz width channel with regulatory rule:                                                                                                                                                  
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302618] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                            
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302622] cfg80211: Updating information on frequency 2427 MHz for a 20 MHz width channel with regulatory rule:                                                                                                                                                   
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302627] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                             
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302630] cfg80211: Updating information on frequency 2432 MHz for a 20 MHz width channel with regulatory ru le:                                                                                                                                                     
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302635] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                               
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302639] cfg80211: Updating information on frequency 2437 MHz for a 20 MHz width channel with regulatory ru  le:                                                                                                                                                     
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302643] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                               
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302647] cfg80211: Updating information on frequency 2442 MHz for a 20 MHz width channel with regulatory ru  le:                                                                                                                                                     
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302652] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                               
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302655] cfg80211: Updating information on frequency 2447 MHz for a 20 MHz width channel with regulatory ru  le:                                                                                                                                                     
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302660] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                              
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302664] cfg80211: Updating information on frequency 2452 MHz for a 20 MHz width channel with regulatory ru le:                                                                                                                                                    
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302668] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)                              
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302672] cfg80211: Updating information on frequency 2457 MHz for a 20 MHz width channel with regulatory rule:
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302677] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302680] cfg80211: Updating information on frequency 2462 MHz for a 20 MHz width channel with regulatory rule:
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302685] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302690] cfg80211: Updating information on frequency 2467 MHz for a 20 MHz width channel with regulatory rule:
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302694] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302698] cfg80211: Updating information on frequency 2472 MHz for a 20 MHz width channel with regulatory rule:
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302703] cfg80211: 2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302706] cfg80211: Disabling freq 2484 MHz
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302713] cfg80211: World regulatory domain updated:
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302716] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302721] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302726] cfg80211:   (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302730] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302735] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.302739] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Mar 26 23:10:13 doug-kubuntu kernel: [  121.329820] usb 1-2: ath9k_htc: USB layer deinitialized
Mar 26 23:10:13 doug-kubuntu kernel: [  121.329966] usb 1-3: USB disconnect, device number 4
Mar 26 23:10:14 doug-kubuntu kernel: [  122.020091] timeout: still 1 active urbs on EP #83
Mar 26 23:10:15 doug-kubuntu kernel: [  123.017801] timeout: still 1 active urbs on EP #83

*Note that the first two lines of the log are similar to the log output when I was using a USB hub with identical symptoms

I suspected that the webcam was faulty, like I suspect a USB hub of mine was. However, if I plug the webcam in one of the USB ports mounted to the front of my computer case, I can use it fine; my wifi adapter still works, and I can use the webcam in skype.

But if I then plug the wifi adapter in the second USB port next to the webcam on the front, they both "break" when I use the webcam. Ideally, I want to use only the back USB ports for both my wifi adapter and my webcam. What is the cause of this? Is my webcam faulty?

hardware info:

  • webcam model: Microsoft LifeCam VX-5000 Analog Mono
  • wifi adapter model: TP-Link TL-WN722N

Update: While I was trying to figure out how to "map out the USB ports to the motherboard's USB controllers & root hubs", I came across the following question on askubuntu, My USB ports randomly stop working till a reboot?, and separately tried both acpi=force irqpoll and noacpi in my boot options (added to the line GRUB_CMDLINE_LINUX in /etc/default/grub and then ran sudo update-grub)

share|improve this question
    
You probably need to map out the USB ports to the motherboard's USB controllers & root hubs. Seems like the webcam does not play nicely when it has to share a USB host controller with other client devices. –  sawdust Mar 27 '13 at 5:59
    
@sawdust would you care to post an answer with more information on how to do that? I was unable to understand what you suggested from your brief comment. –  drdrez Mar 27 '13 at 14:21
    
Plug in a USB device, and execute the lsusb command. Record the location of that device. Repeat for each USB port of your PC. Some ports will be connected to the same bus and USB controller through the built-in root hubs. –  sawdust Mar 28 '13 at 21:24

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