I am using some custom hardware and am attempting to connect a Quectel EC21 modem via the USB port.
With the modem not connected i get
root@colibri-imx6ull:~# lsusb
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
I believe this is showing that my device tree has successfully initiated the host usb device.
When i then connect the GSM modem to the USB port i get
root@colibri-imx6ull:~# lsusb
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
root@colibri-imx6ull:~# [ 73.444264] usb 1-1: new high-speed USB device number 6 using ci_hdrc
[ 73.614238] usb 1-1: device no response, device descriptor read/64, error -71
[ 73.894240] usb 1-1: device no response, device descriptor read/64, error -71
[ 74.164231] usb 1-1: new high-speed USB device number 7 using ci_hdrc
[ 74.334304] usb 1-1: device no response, device descriptor read/64, error -71
[ 74.614244] usb 1-1: device no response, device descriptor read/64, error -71
[ 74.734380] usb usb1-port1: attempt power cycle
[ 75.224215] usb 1-1: new high-speed USB device number 8 using ci_hdrc
[ 75.674220] usb 1-1: device not accepting address 8, error -71
[ 75.824291] usb 1-1: new high-speed USB device number 9 using ci_hdrc
[ 76.274247] usb 1-1: device not accepting address 9, error -71
[ 76.280357] usb usb1-port1: unable to enumerate USB device
Question : Is this just showing that the USB device has been detected but there is no driver installed ?
(Trying to figure out if i have to fix the device tree OR install a driver in the kernel build)
Does the same modem work on a Toradex carrier board such as the Viola?
Error 71 means protocol error, which can be due to many things, including signal integrity issues. Are the USB data traces on your board correctly impedance matched? Does any other USB device work on the same port (a keyboard, an USB drive, etc)?