Support using different FFT swicth seed per fft_r2_pipe instance index.

libraries/dsp/fft/src/vhdl/fft_lfsr.vhd

@@ -21,12 +21,20 @@
 -- Author: ported by E. Kooistra, original 2004 by W. Lubberhuizen / W. Poeisz
 -- Purpose: Scramble quantization noise crosstalk between two real inputs
 -- Description: Ported from LOFAR1, see readme_lofar1.txt
--- Remark: Copy from applications/lofar1/RSP/pft2/src/vhdl/pft_lfsr.vhd
+-- Remark:
+-- . Copy from applications/lofar1/RSP/pft2/src/vhdl/pft_lfsr.vhd
+-- . The g_seed must be > 0 for LFSR period is 2**c_fft_lfsr_len - 1. Value
+--   g_seed = 0 causes the LFSR to remain stuck at 0.
 
 LIBRARY IEEE;
 USE IEEE.std_logic_1164.ALL;
+USE work.fft_pkg.ALL;
 
 ENTITY fft_lfsr IS
+  GENERIC (
+    g_seed1 : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := c_fft_switch_seed1;
+    g_seed2 : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := c_fft_switch_seed2
+  );
   PORT (
     in_en          : IN  STD_LOGIC;
     out_bit1       : OUT STD_LOGIC;
@@ -43,23 +51,23 @@ ARCHITECTURE rtl OF fft_lfsr IS
   -- x^41 + x^20 + 1  and x^41 + x^3 + 1  
   -- see XAPP217
   
-  CONSTANT c_max : NATURAL := 41;
+  CONSTANT c_len : NATURAL := c_fft_lfsr_len;  -- = 41, same for both trinomials
   CONSTANT c1    : NATURAL := 20;
   CONSTANT c2    : NATURAL := 3;  
     
-  SIGNAL s1      : STD_LOGIC_VECTOR(c_max-1 DOWNTO 0);
-  SIGNAL nxt_s1  : STD_LOGIC_VECTOR(c_max-1 DOWNTO 0);
-  
-  SIGNAL s2      : STD_LOGIC_VECTOR(c_max-1 DOWNTO 0);
-  SIGNAL nxt_s2  : STD_LOGIC_VECTOR(c_max-1 DOWNTO 0);
+  SIGNAL s1      : STD_LOGIC_VECTOR(c_len-1 DOWNTO 0);
+  SIGNAL nxt_s1  : STD_LOGIC_VECTOR(c_len-1 DOWNTO 0);
   
+  SIGNAL s2      : STD_LOGIC_VECTOR(c_len-1 DOWNTO 0);
+  SIGNAL nxt_s2  : STD_LOGIC_VECTOR(c_len-1 DOWNTO 0);
 
 BEGIN
+
   p_reg : PROCESS(rst,clk)
   BEGIN
     IF rst='1' THEN
-      s1 <= "01000101011101110101001011111000101100001";
-      s2 <= "11011001000101001011011001110101100101100";
+      s1 <= g_seed1;
+      s2 <= g_seed2;
     ELSIF rising_edge(clk) THEN
       s1 <= nxt_s1;      
       s2 <= nxt_s2;      
@@ -75,16 +83,16 @@ BEGIN
     nxt_s2 <= s2;    
     IF in_en = '1' THEN
       -- shift      
-      nxt_s1(c_max-1 DOWNTO 1) <= s1(c_max-2 DOWNTO 0);      
-      nxt_s2(c_max-1 DOWNTO 1) <= s2(c_max-2 DOWNTO 0);      
+      nxt_s1(c_len-1 DOWNTO 1) <= s1(c_len-2 DOWNTO 0);
+      nxt_s2(c_len-1 DOWNTO 1) <= s2(c_len-2 DOWNTO 0);
       
       -- feedback 1
-      nxt_s1(0) <= s1(c_max-1);
-      nxt_s2(0) <= s2(c_max-1);
+      nxt_s1(0) <= s1(c_len-1);
+      nxt_s2(0) <= s2(c_len-1);
       
       -- feedback 2
-      nxt_s1(c1) <= s1(c_max-1) xor s1(c1-1);
-      nxt_s2(c2) <= s2(c_max-1) xor s2(c2-1);
+      nxt_s1(c1) <= s1(c_len-1) xor s1(c1-1);
+      nxt_s2(c2) <= s2(c_len-1) xor s2(c2-1);
     END IF;
   END PROCESS;
 

libraries/dsp/fft/src/vhdl/fft_pkg.vhd

@@ -25,6 +25,13 @@ use common_lib.common_pkg.all;
 
 package fft_pkg is
 
+  -- Default FFT switch and unswitch seeds from LOFAR1
+  constant c_fft_lfsr_len      : natural := 41;
+  constant c_fft_switch_seed1  : std_logic_vector(c_fft_lfsr_len-1 DOWNTO 0) := "01000101011101110101001011111000101100001";
+  constant c_fft_switch_seed2  : std_logic_vector(c_fft_lfsr_len-1 DOWNTO 0) := "11011001000101001011011001110101100101100";
+
+  function fft_switch_new_seed(seed : std_logic_vector; offset : natural) return std_logic_vector;
+
   -- FFT parameters for pipelined FFT (fft_pipe), parallel FFT (fft_par) and wideband FFT (fft_wide)
   type t_fft is record
     use_reorder    : boolean;  -- = false for bit-reversed output, true for normal output
@@ -68,6 +75,11 @@ end package fft_pkg;
 
 package body fft_pkg is
 
+  function fft_switch_new_seed(seed : std_logic_vector; offset : natural) return std_logic_vector is
+  begin
+    return INCR_UVEC(seed, offset);  -- make new unique seed
+  end;
+
   function fft_r2_parameter_asserts(g_fft : t_fft) return boolean is
   begin
     -- nof_points

libraries/dsp/fft/src/vhdl/fft_r2_pipe.vhd

@@ -66,6 +66,7 @@ use work.fft_pkg.all;
 
 entity fft_r2_pipe is
   generic (
+    g_instance_index     : natural := 0;           -- used for FFT switch seed
     g_fft                : t_fft := c_fft;                   -- generics for the FFT
     g_pipeline           : t_fft_pipeline := c_fft_pipeline; -- generics for pipelining in each stage, defined in rTwoSDF_lib.rTwoSDFPkg
     g_dont_flip_channels : boolean := false;       -- generic to prevent re-ordering of the channels
@@ -92,6 +93,8 @@ architecture str of fft_r2_pipe is
   constant c_switch_sz_w        : natural := ceil_log2(g_fft.nof_points) + g_fft.nof_chan;
   constant c_switch_dat_w       : natural := g_fft.in_dat_w + 1;  -- add 1 extra bit to fit negation of most negative value per real input switch function
   constant c_unswitch_dat_w     : natural := g_fft.out_dat_w;  -- no need for extra bit, because most negative value cannot occur in output
+  constant c_switch_seed1       : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := fft_switch_new_seed(c_fft_switch_seed1, g_instance_index);
+  constant c_switch_seed2       : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := fft_switch_new_seed(c_fft_switch_seed2, g_instance_index);
   constant c_nof_stages         : natural := ceil_log2(g_fft.nof_points);
   constant c_stage_offset       : natural := true_log2(g_fft.wb_factor);                         -- Stage offset is required for twiddle generation in wideband fft
   constant c_in_scale_w         : natural := g_fft.stage_dat_w - g_fft.in_dat_w - sel_a_b(g_fft.guard_enable, g_fft.guard_w, 0);              
@@ -143,6 +146,8 @@ begin
   u_switch : ENTITY work.fft_switch
   GENERIC MAP (
     g_switch_en => c_switch_en,
+    g_seed1     => c_switch_seed1,
+    g_seed2     => c_switch_seed2,
     g_fft_sz_w  => c_switch_sz_w,
     g_dat_w     => c_switch_dat_w
   )
@@ -303,6 +308,8 @@ begin
   u_unswitch : ENTITY work.fft_unswitch
   GENERIC MAP (
     g_switch_en => c_switch_en,
+    g_seed1     => c_switch_seed1,
+    g_seed2     => c_switch_seed2,
     g_fft_sz_w  => c_switch_sz_w,
     g_dat_w     => c_unswitch_dat_w
   )

libraries/dsp/fft/src/vhdl/fft_switch.vhd

@@ -46,10 +46,13 @@
 LIBRARY IEEE, common_lib;
 USE IEEE.std_logic_1164.ALL;
 USE common_lib.common_pkg.ALL;
+USE work.fft_pkg.ALL;
 
 ENTITY fft_switch IS
   GENERIC (
     g_switch_en : BOOLEAN := FALSE;
+    g_seed1     : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := c_fft_switch_seed1;
+    g_seed2     : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := c_fft_switch_seed2;
     g_fft_sz_w  : NATURAL;
     g_dat_w     : NATURAL
   );
@@ -156,6 +159,10 @@ BEGIN
     END PROCESS;
 
     u_fft_lfsr: ENTITY work.fft_lfsr
+    GENERIC MAP (
+      g_seed1 => g_seed1,
+      g_seed2 => g_seed2
+    )
     PORT MAP (
       clk      => clk,
       rst      => rst,

libraries/dsp/fft/src/vhdl/fft_unswitch.vhd

@@ -31,10 +31,13 @@
 LIBRARY IEEE, common_lib;
 USE IEEE.std_logic_1164.ALL;
 USE common_lib.common_pkg.ALL;
+USE work.fft_pkg.ALL;
 
 ENTITY fft_unswitch IS
   GENERIC (
     g_switch_en : BOOLEAN := FALSE;
+    g_seed1     : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := c_fft_switch_seed1;
+    g_seed2     : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := c_fft_switch_seed2;
     g_fft_sz_w  : NATURAL;
     g_dat_w     : NATURAL
   );
@@ -147,6 +150,10 @@ BEGIN
     END PROCESS;
 
     u_fft_lfsr: ENTITY work.fft_lfsr
+    GENERIC MAP (
+      g_seed1 => g_seed1,
+      g_seed2 => g_seed2
+    )
     PORT MAP (
       clk      => clk,
       rst      => rst,

libraries/dsp/fft/tb/vhdl/tb_fft_switch.vhd

@@ -52,9 +52,11 @@ LIBRARY IEEE, common_lib;
 USE IEEE.std_logic_1164.ALL;
 USE common_lib.common_pkg.ALL;
 USE common_lib.tb_common_pkg.ALL;
+USE work.fft_pkg.ALL;
 
 ENTITY tb_fft_switch IS
   GENERIC (
+    g_instance_index     : NATURAL := 0;
     g_switch_en          : BOOLEAN := TRUE;
     g_in_val_gaps        : BOOLEAN := TRUE;
     g_increment_at_val   : BOOLEAN := TRUE;
@@ -76,6 +78,9 @@ ARCHITECTURE tb OF tb_fft_switch IS
 
   CONSTANT c_dly           : NATURAL := 4;  -- pipeling in fft_switch, mux,  fft_unswitch and demux
 
+  constant c_switch_seed1  : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := fft_switch_new_seed(c_fft_switch_seed1, g_instance_index);
+  constant c_switch_seed2  : STD_LOGIC_VECTOR(c_fft_lfsr_len-1 DOWNTO 0) := fft_switch_new_seed(c_fft_switch_seed2, g_instance_index);
+
   SIGNAL tb_end            : STD_LOGIC := '0';
   SIGNAL rst               : STD_LOGIC := '1';
   SIGNAL clk               : STD_LOGIC := '0';
@@ -185,6 +190,8 @@ BEGIN
   u_fft_switch : ENTITY work.fft_switch
   GENERIC MAP (
     g_switch_en => g_switch_en,
+    g_seed1     => c_switch_seed1,
+    g_seed2     => c_switch_seed2,
     g_fft_sz_w  => g_fft_size_w,
     g_dat_w     => c_dat_w
   )
@@ -227,6 +234,8 @@ BEGIN
   u_fft_unswitch : ENTITY work.fft_unswitch
   GENERIC MAP (
     g_switch_en => g_switch_en,
+    g_seed1     => c_switch_seed1,
+    g_seed2     => c_switch_seed2,
     g_fft_sz_w  => g_fft_size_w,
     g_dat_w     => c_dat_w
   )

libraries/dsp/wpfb/src/vhdl/wpfb_unit_dev.vhd

@@ -597,6 +597,7 @@ begin
       gen_fft_r2_pipe_streams: for S in 0 to g_wpfb.nof_wb_streams-1 generate
         u_fft_r2_pipe : entity fft_lib.fft_r2_pipe
         generic map(
+          g_instance_index     => S,
           g_fft                => c_fft,
           g_pipeline           => g_wpfb.fft_pipeline,
           g_dont_flip_channels => g_dont_flip_channels,