ISE 14.7 openrisc fusesoc PAR er

The router has detected an unroutable situation for one or more connections. The router will finish the rest of the
   design and leave them as unrouted. The cause of this behavior is either an issue with the placement or unroutable placement constraints.
   To allow you to use FPGA editor to isolate the problems, the following is a list of (up to 10) such unroutable connections:
	 Unroutable 	 signal: dvi_clk 	 pin:  dvi_gen0/PCLK_GEN_INST/CLKIN