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, 166 insertions, 0 deletions

diff --git a/fpga/usrp3/lib/extramfifo/ext_fifo.v b/fpga/usrp3/lib/extramfifo/ext_fifo.v
new file mode 100644
index 000000000..8ec32b45d
--- /dev/null
+++ b/fpga/usrp3/lib/extramfifo/ext_fifo.v
@@ -0,0 +1,166 @@
+//
+// Copyright 2011 Ettus Research LLC
+// Copyright 2018 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+// 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/>.
+//
+
+//
+// FIFO backed by an off chip ZBT/NoBL SRAM.
+//
+// This module and its sub-hierarchy implment a FIFO capable of sustaining 
+// a data throughput rate of at least int_clk/2 * 36bits and bursts of int_clk * 36bits.
+//
+// This has been designed and tested for an int_clk of 100MHz and an ext_clk of 125MHz,
+// your milage may vary with other clock ratio's especially those where int_clk < ext_clk.
+// Testing has also exclusively used a rst signal synchronized to int_clk.
+//
+// Interface operation mimics a Xilinx FIFO configured as "First Word Fall Through",
+// though signal naming differs.
+//
+// For FPGA use registers interfacing directly with signals prefixed "RAM_*" should be 
+// packed into the IO ring.
+//
+
+module ext_fifo
+  #(parameter INT_WIDTH=36,EXT_WIDTH=18,RAM_DEPTH=19,FIFO_DEPTH=19)
+    (
+     input int_clk,
+     input ext_clk,
+     input rst,
+     input [EXT_WIDTH-1:0] RAM_D_pi,
+     output [EXT_WIDTH-1:0] RAM_D_po,
+     output RAM_D_poe,
+     output [RAM_DEPTH-1:0] RAM_A,
+     output RAM_WEn,
+     output RAM_CENn,
+     output RAM_LDn,
+     output RAM_OEn,
+     output RAM_CE1n,
+     input [INT_WIDTH-1:0] datain,
+     input src_rdy_i,                // WRITE
+     output dst_rdy_o,               // not FULL
+     output [INT_WIDTH-1:0] dataout,
+     output src_rdy_o,               // not EMPTY
+     input dst_rdy_i                  // READ
+     );
+
+   wire [EXT_WIDTH-1:0] write_data;
+   wire [EXT_WIDTH-1:0] read_data;
+   wire 		full1, empty1;
+   wire 		almost_full2, almost_full2_spread, full2, empty2;
+   wire [FIFO_DEPTH-1:0] capacity;
+   wire 		 space_avail;
+   wire 		 data_avail;
+		 
+   // These next 2 lines here purely because ICARUS is crap at handling generate statements.
+   // Empirically this has been determined to make simulations work.
+   wire 		 read_input_fifo = space_avail & ~empty1;
+   wire 		 write_output_fifo = data_avail;
+   
+   assign 		 src_rdy_o = ~empty2;
+   assign 		 dst_rdy_o = ~full1;
+
+   // External FIFO running at ext clock rate  and 18 or 36 bit width.
+   nobl_fifo  #(.WIDTH(EXT_WIDTH),.RAM_DEPTH(RAM_DEPTH),.FIFO_DEPTH(FIFO_DEPTH))
+     nobl_fifo_i1
+       (   
+	   .clk(ext_clk),
+	   .rst(rst),
+	   .RAM_D_pi(RAM_D_pi),
+	   .RAM_D_po(RAM_D_po),
+	   .RAM_D_poe(RAM_D_poe),
+	   .RAM_A(RAM_A),
+	   .RAM_WEn(RAM_WEn),
+	   .RAM_CENn(RAM_CENn),
+	   .RAM_LDn(RAM_LDn),
+	   .RAM_OEn(RAM_OEn),
+	   .RAM_CE1n(RAM_CE1n),
+	   .write_data(write_data),
+	   .write_strobe(~empty1 ),
+	   .space_avail(space_avail),
+	   .read_data(read_data),
+	   .read_strobe(~almost_full2_spread),
+	   .data_avail(data_avail),
+	   .capacity(capacity)
+	   );
+
+   generate
+      if (EXT_WIDTH == 18 && INT_WIDTH == 36) begin: fifo_g1
+	 // FIFO buffers data from UDP engine into external FIFO clock domain.
+	 fifo_xlnx_512x36_2clk_36to18 fifo_xlnx_512x36_2clk_36to18_i1 (
+								       .rst(rst),
+								       .wr_clk(int_clk),
+								       .rd_clk(ext_clk),
+								       .din(datain), // Bus [35 : 0] 
+								       .wr_en(src_rdy_i), 
+								       .rd_en(read_input_fifo),    		
+								       .dout(write_data), // Bus [17 : 0]
+								       .full(full1),			
+							               .empty(empty1));
+
+	 
+	 // FIFO buffers data read from external FIFO into DSP clk domain and to TX DSP.
+	 fifo_xlnx_512x36_2clk_18to36 fifo_xlnx_512x36_2clk_18to36_i1 (
+								       .rst(rst),
+								       .wr_clk(ext_clk),
+								       .rd_clk(int_clk),
+								       .din(read_data), // Bus [17 : 0]
+								       .wr_en(write_output_fifo),
+								       .rd_en(dst_rdy_i),
+								       .dout(dataout), // Bus [35 : 0]
+								       .full(full2),
+								       .prog_full(almost_full2),
+								       .empty(empty2));
+      end // block: fifo_g1
+      else if (EXT_WIDTH == 36 && INT_WIDTH == 36) begin: fifo_g1
+	 // FIFO buffers data from UDP engine into external FIFO clock domain.
+	 fifo_xlnx_32x36_2clk fifo_xlnx_32x36_2clk_i1 (
+						       .rst(rst),
+						       .wr_clk(int_clk),
+						       .rd_clk(ext_clk),
+						       .din(datain), // Bus [35 : 0] 
+						       .wr_en(src_rdy_i),
+						       .rd_en(read_input_fifo),
+						       .dout(write_data), // Bus [35 : 0] 
+						       .full(full1),
+						       .empty(empty1));
+	 
+	 // FIFO buffers data read from external FIFO into DSP clk domain and to TX DSP.
+	 fifo_xlnx_512x36_2clk_prog_full fifo_xlnx_32x36_2clk_prog_full_i1 (
+									    .rst(rst),
+									    .wr_clk(ext_clk),
+									    .rd_clk(int_clk),
+									    .din(read_data), // Bus [35 : 0] 
+									    .wr_en(write_output_fifo),
+									    .rd_en(dst_rdy_i),
+									    .dout(dataout), // Bus [35 : 0] 
+									    .full(full2),
+									    .empty(empty2),
+									    .prog_full(almost_full2));
+
+      end    
+   endgenerate
+
+   refill_randomizer #(.BITS(7))
+     refill_randomizer_i1 (
+			   .clk(ext_clk),
+			   .rst(rst),
+			   .full_in(almost_full2),
+			   .full_out(almost_full2_spread)
+			   );
+   
+endmodule // ext_fifo