PS DDR: 4 GB splitted in 2 areas each of 2 GB: only the first 2GB are accessible

The PS DDR of the zynqmp is splitted into 2 regions of 2GB each. the first 2GB from 0x0 to 0x7fffffff and the second 2GB from 0x80000000 to 0xffffffff. The driver doesn't handle properly access to the 4 GB.