Increasing Rocket's memory addressing

[rajatsrao]

Hi @li3tuo4 ,

The default project has 256 MB made available to the Rocket core. I want to increase this to 1 GB. I checked that the address editor for Zynq has 2 GB addressable and I modified the rocketchip_wrapper.v file -

assign S_AXI_araddr = {2'd1, mem_araddr[29:0]};
assign S_AXI_awaddr = {2'd1, mem_awaddr[29:0]};

This should allow it to address memory starting at 1 GB offset and 30 bits means it can address 1 GB of memory. But, with this change, it completely stopped working. Any chisel code/parameters that need to be changed to match?