Ubuntu – USB device not accepting address

Why does lsusb show USB2 devices connected to a USB3 port as being attached to the USB 2 root?

Answer :

In USB 3.0, dual-bus architecture is used to allow both USB 2.0 (Full Speed, Low Speed, or High Speed) and USB 3.0 (SuperSpeed) operations to take place simultaneously, thus providing backward compatibility.

Source: https://en.wikipedia.org/wiki/USB_3.0

For instance, on a machine that contains two 2.0 USB ports and one USB 3.0 port, the output of the lsusb command shows:

Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 2.0 root hub 
Bus 003 Device 002: ID 8087:8004 Intel Corp. 
Bus 003 Device 001: ID 1d6b:0008 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 058f:6386 Alcor Micro Corp. Multi Flash Reader
Bus 002 Device 001: ID 1d6b:0007 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The extra USB 2.0 root hub is part of the USB 3.0 root hub and is available there to provide backward compatibility with USB 2.0 standards. As a result of this, when you connect USB2 devices into USB3 port, they are shown connected to 2.0 root hub.

Is there a way to get the physical rather than logical mapping of USB ports to hubs?

Answer: Use lsusb -t

-t     Tells lsusb to dump the physical USB device hierarchy as a tree.

Source: lsusb man page

Coming back to my original reason for looking into this, is there a way to tell what speed the internal SD card reader is capable of before buying one?

This can be done by using the following steps. Here we are considering a laptop with a built-in card reader from Alcor Micro Corp.

1. Use lsusb command

   $ lsusb 
   Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 2.0 root hub 
   Bus 003 Device 002: ID 8087:8004 Intel Corp. 
   Bus 003 Device 001: ID 1d6b:0008 Linux Foundation 2.0 root hub
   Bus 001 Device 002: ID 058f:6386 Alcor Micro Corp. Multi Flash Reader
   Bus 002 Device 001: ID 1d6b:0007 Linux Foundation 3.0 root hub
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
   

   Find out the Bus number of the card reader. In this example it is 001

2. Use lsusb -t

   $ lsusb -t 
   /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/14p, 480M 
   |__ Port 5: Dev 2, If 0, Class=Mass Storage, Driver=usb-storage, 480M
   

   At the end of each line, the negotiated communication speed for each device is shown in Mbits/s.
   The 480Mbit/s is called "Hi-Speed" and is used with USB2.0.

For USB 3.0, the negotiated communication speed is 5000Mbit/s called "SuperSpeed" (5Gbit/s)

Source: https://en.wikipedia.org/wiki/USB

Result: the card reader from Alcor Micro Corp supports USB 2.0 standards and not USB 3.0 standards as 480M was mentioned in the output.

A possible solution - Blacklisting USB related kernel modules in a trial and error procedure revealed that the ehci-pci kernel module was the cause of the problem.

For a temporary solution, simply remove the kernel module:

sudo rmmod ehci_pci

For a permanent solution, either blacklist the module via kernel boot arguments, e.g.

modprobe.blacklist=ehci_pci

nb. Blacklisting ehci_pci will also prevent kernel module ehci-hcd from getting loaded.

The ehci* kernel modules are the kernel’s USB 2 drivers.

Luckily, the USB 3 kernel modules xhci* support USB 2 devices as well and you will experience no performance loss with these