Merge FPGA repository back into UHD repository

The FPGA codebase was removed from the UHD repository in 2014 to reduce
the size of the repository. However, over the last half-decade, the
split between the repositories has proven more burdensome than it has
been helpful. By merging the FPGA code back, it will be possible to
create atomic commits that touch both FPGA and UHD codebases. Continuous
integration testing is also simplified by merging the repositories,
because it was previously difficult to automatically derive the correct
UHD branch when testing a feature branch on the FPGA repository.

This commit also updates the license files and paths therein.

We are therefore merging the repositories again. Future development for
FPGA code will happen in the same repository as the UHD host code and
MPM code.

== Original Codebase and Rebasing ==

The original FPGA repository will be hosted for the foreseeable future
at its original local location: https://github.com/EttusResearch/fpga/

It can be used for bisecting, reference, and a more detailed history.

The final commit from said repository to be merged here is
05003794e2da61cabf64dd278c45685a7abad7ec. This commit is tagged as
v4.0.0.0-pre-uhd-merge.

If you have changes in the FPGA repository that you want to rebase onto
the UHD repository, simply run the following commands:

- Create a directory to store patches (this should be an empty
  directory):

    mkdir ~/patches

- Now make sure that your FPGA codebase is based on the same state as
  the code that was merged:

    cd src/fpga # Or wherever your FPGA code is stored
    git rebase v4.0.0.0-pre-uhd-merge

  Note: The rebase command may look slightly different depending on what
  exactly you're trying to rebase.

- Create a patch set for your changes versus v4.0.0.0-pre-uhd-merge:

    git format-patch v4.0.0.0-pre-uhd-merge -o ~/patches

  Note: Make sure that only patches are stored in your output directory.
  It should otherwise be empty. Make sure that you picked the correct
  range of commits, and only commits you wanted to rebase were exported
  as patch files.

- Go to the UHD repository and apply the patches:

    cd src/uhd # Or wherever your UHD repository is stored
    git am --directory fpga ~/patches/*
    rm -rf ~/patches # This is for cleanup

== Contributors ==

The following people have contributed mainly to these files (this list
is not complete):

Co-authored-by: Alex Williams <alex.williams@ni.com>
Co-authored-by: Andrej Rode <andrej.rode@ettus.com>
Co-authored-by: Ashish Chaudhari <ashish@ettus.com>
Co-authored-by: Ben Hilburn <ben.hilburn@ettus.com>
Co-authored-by: Ciro Nishiguchi <ciro.nishiguchi@ni.com>
Co-authored-by: Daniel Jepson <daniel.jepson@ni.com>
Co-authored-by: Derek Kozel <derek.kozel@ettus.com>
Co-authored-by: EJ Kreinar <ej@he360.com>
Co-authored-by: Humberto Jimenez <humberto.jimenez@ni.com>
Co-authored-by: Ian Buckley <ian.buckley@gmail.com>
Co-authored-by: Jörg Hofrichter <joerg.hofrichter@ni.com>
Co-authored-by: Jon Kiser <jon.kiser@ni.com>
Co-authored-by: Josh Blum <josh@joshknows.com>
Co-authored-by: Jonathon Pendlum <jonathan.pendlum@ettus.com>
Co-authored-by: Martin Braun <martin.braun@ettus.com>
Co-authored-by: Matt Ettus <matt@ettus.com>
Co-authored-by: Michael West <michael.west@ettus.com>
Co-authored-by: Moritz Fischer <moritz.fischer@ettus.com>
Co-authored-by: Nick Foster <nick@ettus.com>
Co-authored-by: Nicolas Cuervo <nicolas.cuervo@ettus.com>
Co-authored-by: Paul Butler <paul.butler@ni.com>
Co-authored-by: Paul David <paul.david@ettus.com>
Co-authored-by: Ryan Marlow <ryan.marlow@ettus.com>
Co-authored-by: Sugandha Gupta <sugandha.gupta@ettus.com>
Co-authored-by: Sylvain Munaut <tnt@246tNt.com>
Co-authored-by: Trung Tran <trung.tran@ettus.com>
Co-authored-by: Vidush Vishwanath <vidush.vishwanath@ettus.com>
Co-authored-by: Wade Fife <wade.fife@ettus.com>

1 files changed, 141 insertions, 0 deletions

diff --git a/fpga/usrp2/fifo/fifo_2clock.v b/fpga/usrp2/fifo/fifo_2clock.v
new file mode 100644
index 000000000..98aab18a5
--- /dev/null
+++ b/fpga/usrp2/fifo/fifo_2clock.v
@@ -0,0 +1,141 @@
+//
+// Copyright 2011-2012 Ettus Research LLC
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+// FIXME ignores the AWIDTH (fifo size) parameter
+
+module fifo_2clock
+  #(parameter WIDTH=36, SIZE=6)
+   (input wclk, input [WIDTH-1:0] datain, input src_rdy_i, output dst_rdy_o, output [15:0] space,
+    input rclk, output [WIDTH-1:0] dataout, output src_rdy_o, input dst_rdy_i, output [15:0] occupied,
+    input arst);
+   
+   wire [SIZE:0] level_rclk, level_wclk; // xilinx adds an extra bit if you ask for accurate levels
+   wire 	 full, empty, write, read;
+
+   assign dst_rdy_o  = ~full;
+   assign src_rdy_o  = ~empty;
+   assign write      = src_rdy_i & dst_rdy_o;
+   assign read 	     = src_rdy_o & dst_rdy_i;
+
+   generate
+      if((WIDTH <= 36) && (WIDTH > 19)) begin
+	wire [35:0] data_in_wide, data_out_wide;
+	assign data_in_wide[WIDTH-1:0] = datain;
+	assign dataout = data_out_wide[WIDTH-1:0];
+	if(SIZE==9)
+	  fifo_xlnx_512x36_2clk fifo_xlnx_512x36_2clk
+	       (.rst(arst),
+		.wr_clk(wclk),.din(data_in_wide),.full(full),.wr_en(write),.wr_data_count(level_wclk),
+		.rd_clk(rclk),.dout(data_out_wide),.empty(empty),.rd_en(read),.rd_data_count(level_rclk) );
+	else if(SIZE==11)
+	  fifo_xlnx_2Kx36_2clk fifo_xlnx_2Kx36_2clk 
+		     (.rst(arst),
+		      .wr_clk(wclk),.din(data_in_wide),.full(full),.wr_en(write),.wr_data_count(level_wclk),
+		      .rd_clk(rclk),.dout(data_out_wide),.empty(empty),.rd_en(read),.rd_data_count(level_rclk) );
+	else if(SIZE==6)
+	  fifo_xlnx_64x36_2clk fifo_xlnx_64x36_2clk 
+		     (.rst(arst),
+		      .wr_clk(wclk),.din(data_in_wide),.full(full),.wr_en(write),.wr_data_count(level_wclk),
+		      .rd_clk(rclk),.dout(data_out_wide),.empty(empty),.rd_en(read),.rd_data_count(level_rclk) );
+	else
+	  fifo_xlnx_512x36_2clk fifo_xlnx_512x36_2clk
+	       (.rst(arst),
+		.wr_clk(wclk),.din(data_in_wide),.full(full),.wr_en(write),.wr_data_count(level_wclk),
+		.rd_clk(rclk),.dout(data_out_wide),.empty(empty),.rd_en(read),.rd_data_count(level_rclk) );
+      end
+      else if((WIDTH <= 19) && (SIZE <= 4)) begin
+	wire [18:0] data_in_wide, data_out_wide;
+	assign data_in_wide[WIDTH-1:0] = datain;
+	assign dataout = data_out_wide[WIDTH-1:0];
+	fifo_xlnx_16x19_2clk fifo_xlnx_16x19_2clk
+	  (.rst(arst),
+	   .wr_clk(wclk),.din(data_in_wide),.full(full),.wr_en(write),.wr_data_count(level_wclk),
+	   .rd_clk(rclk),.dout(data_out_wide),.empty(empty),.rd_en(read),.rd_data_count(level_rclk) );
+      end
+   endgenerate
+
+   assign occupied  = {{(16-SIZE-1){1'b0}},level_rclk};
+   assign space     = ((1<<SIZE)+1)-level_wclk;
+   
+endmodule // fifo_2clock
+
+/*
+`else
+   // ISE sucks, so the following doesn't work properly
+
+   reg [AWIDTH-1:0] wr_addr, rd_addr;
+   wire [AWIDTH-1:0] wr_addr_rclk, rd_addr_wclk;
+   wire [AWIDTH-1:0] next_rd_addr;
+   wire 	    enb_read;
+   
+   // Write side management
+   wire [AWIDTH-1:0] next_wr_addr = wr_addr + 1;
+   always @(posedge wclk or posedge arst)
+     if(arst)
+       wr_addr <= 0;
+     else if(write)
+       wr_addr <= next_wr_addr;
+   assign 	    full = (next_wr_addr == rd_addr_wclk);
+
+   //  RAM for data storage.  Data out is registered, complicating the
+   //     read side logic
+   ram_2port #(.DWIDTH(DWIDTH),.AWIDTH(AWIDTH)) mac_rx_ff_ram
+     (.clka(wclk),.ena(1'b1),.wea(write),.addra(wr_addr),.dia(datain),.doa(),
+      .clkb(rclk),.enb(enb_read),.web(1'b0),.addrb(next_rd_addr),.dib(0),.dob(dataout) );
+
+   // Read side management
+   reg 		    data_valid;
+   assign 	    empty = ~data_valid;
+   assign 	    next_rd_addr = rd_addr + data_valid;
+   assign 	    enb_read = read | ~data_valid;
+
+   always @(posedge rclk or posedge arst)
+     if(arst)
+       rd_addr <= 0;
+     else if(read)
+       rd_addr <= rd_addr + 1;
+
+   always @(posedge rclk or posedge arst)
+     if(arst)
+       data_valid <= 0;
+     else
+       if(read & (next_rd_addr == wr_addr_rclk))
+	 data_valid <= 0;
+       else if(next_rd_addr != wr_addr_rclk)
+	 data_valid <= 1;
+	 
+   // Send pointers across clock domains via gray code
+   gray_send #(.WIDTH(AWIDTH)) send_wr_addr
+     (.clk_in(wclk),.addr_in(wr_addr),
+      .clk_out(rclk),.addr_out(wr_addr_rclk) );
+   
+   gray_send #(.WIDTH(AWIDTH)) send_rd_addr
+     (.clk_in(rclk),.addr_in(rd_addr),
+      .clk_out(wclk),.addr_out(rd_addr_wclk) );
+
+   // Generate fullness info, these are approximate and may be delayed 
+   // and are only for higher-level flow control.  
+   // Only full and empty are guaranteed exact.
+   always @(posedge wclk) 
+     level_wclk <= wr_addr - rd_addr_wclk;
+   always @(posedge rclk) 
+     level_rclk <= wr_addr_rclk - rd_addr;
+`endif
+endmodule // fifo_2clock
+
+*/