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, 117 insertions, 0 deletions

diff --git a/fpga/usrp3/lib/extramfifo/nobl_fifo.v b/fpga/usrp3/lib/extramfifo/nobl_fifo.v
new file mode 100644
index 000000000..e4fa1422e
--- /dev/null
+++ b/fpga/usrp3/lib/extramfifo/nobl_fifo.v
@@ -0,0 +1,117 @@
+//
+// 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/>.
+//
+
+// Since this FIFO uses a ZBT/NoBL SRAM for its storage which is a since port 
+// device it can only sustain data throughput at half the RAM clock rate.
+// Fair arbitration to ensure this occurs is included in this logic and
+// requests for transactions that can not be completed are held off.
+// This FIFO requires a an external signal driving read_strobe that assures space for at least 6
+// reads since this the theopretical maximum number in flight due to pipeling.
+
+module nobl_fifo
+  #(parameter WIDTH=18,RAM_DEPTH=19,FIFO_DEPTH=19)
+    (   
+	input clk,
+	input rst,
+	input [WIDTH-1:0] RAM_D_pi,
+	output [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 [WIDTH-1:0] write_data,
+	input write_strobe,
+	output reg space_avail,
+	output  [WIDTH-1:0] read_data,
+	input read_strobe,                    // Triggers a read, result in approximately 6 cycles.
+	output  data_avail,                    // Qulaifys read data available this cycle on read_data.
+	output reg [FIFO_DEPTH-1:0] capacity
+	);
+
+   //reg [FIFO_DEPTH-1:0] capacity;
+   reg [FIFO_DEPTH-1:0] wr_pointer;
+   reg [FIFO_DEPTH-1:0] rd_pointer;
+   wire [RAM_DEPTH-1:0] address;
+   reg 			data_avail_int;  // Internal not empty flag.
+   
+   assign 	    read = read_strobe && data_avail_int;
+   assign 	    write = write_strobe && space_avail;
+
+   // When a read and write collision occur, supress the space_avail flag next cycle
+   // and complete write followed by read over 2 cycles. This forces balanced arbitration
+   // and makes for a simple logic design.
+
+   always @(posedge clk)
+     if (rst)
+       begin
+	  capacity <= (1 << FIFO_DEPTH) - 1;
+	  wr_pointer <= 0;
+	  rd_pointer <= 0;
+	  space_avail <= 1;
+	  data_avail_int <= 0;
+       end
+     else	  
+       begin
+	  // No space available if:
+	  // Capacity is already zero; Capacity is 1 and write is asserted (lookahead); both read and write are asserted (collision)
+	  space_avail <= ~((capacity == 0) || (read&&write) || ((capacity == 1) && write) );
+	  // Capacity has 1 cycle delay so look ahead here for corner case of read of last item in FIFO.
+	  data_avail_int <= ~((capacity == ((1 << FIFO_DEPTH)-1))  || ((capacity == ((1 << FIFO_DEPTH)-2)) && (~write && read))  );
+	  wr_pointer <= wr_pointer + write;
+	  rd_pointer <= rd_pointer + (~write && read); 
+	  capacity <= capacity - write + (~write && read) ;
+       end // else: !if(rst)
+
+   assign address = write ? wr_pointer : rd_pointer;
+   assign enable = write || read; 
+
+
+   //
+   // Simple NoBL SRAM interface, 4 cycle read latency.
+   // Read/Write arbitration via temprary application of empty/full flags.
+   //
+   nobl_if #(.WIDTH(WIDTH),.DEPTH(RAM_DEPTH))
+     nobl_if_i1
+       (
+	.clk(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),
+	.address(address),
+	.data_out(write_data),
+	.data_in(read_data),
+	.data_in_valid(data_avail),
+	.write(write),
+	.enable(enable)
+	);
+
+   
+
+endmodule // nobl_fifo