(https://wiki.archlinux.org/index.php/Xilinx_ISE_WebPACK#Xilinx_Platform_Cable_USB-JTAG_Drivers)

$ cd /opt/Xilinx/
$ sudo git clone git://git.zerfleddert.de/usb-driver
$ cd usb-driver/
$ apt install fxload libusb-dev
$ sudo nano Makefile
 #comment -m32
$ sudo make
$ ./setup_pcusb /opt/Xilinx/14.7/ISE_DS/ISE
$ sudo udevadm control --reload-rules

Unplug and replug - and you should see a red light.

You may need to set the following env variable after sourcing a settings file.

$ export LD_PRELOAD=/opt/Xilinx/usb-driver/libusb-driver.so
$ impact