From 71e6c74d17975056448e53b5b271de21da1f4541 Mon Sep 17 00:00:00 2001
From: Guilherme Ricioli <guilherme.riciolic@gmail.com>
Date: Wed, 23 Oct 2024 18:27:53 -0300
Subject: [PATCH] xwb_fofb_shaper_filt.vhd: optimize registers usage

Don't instantiate registers for the coefficients of non-instantiated
biquads. Handle their (improper?) access by returning 0 to readings and
doing nothing to writings.

This commit frees 360 coefficients registers.
---
 .../fofb_shaper_filt/xwb_fofb_shaper_filt.vhd | 81 ++++++++++---------
 .../fofb_shaper_filt_coeffs.dat               | 24 +++---
 .../xwb_fofb_shaper_filt_tb.vhd               |  6 ++
 3 files changed, 62 insertions(+), 49 deletions(-)

diff --git a/hdl/modules/fofb_shaper_filt/xwb_fofb_shaper_filt.vhd b/hdl/modules/fofb_shaper_filt/xwb_fofb_shaper_filt.vhd
index de381d3..eb03cd5 100644
--- a/hdl/modules/fofb_shaper_filt/xwb_fofb_shaper_filt.vhd
+++ b/hdl/modules/fofb_shaper_filt/xwb_fofb_shaper_filt.vhd
@@ -139,7 +139,7 @@ ARCHITECTURE behave OF xwb_fofb_shaper_filt IS
       (OTHERS => c_WB_FOFB_SHAPER_FILT_REGS_COEFFS_O_IFC_0s);
 
   SIGNAL coeffs : t_fofb_shaper_filt_coeffs(g_CHANNELS-1 DOWNTO 0)(
-                    c_MAX_ABI_BIQUADS-1 DOWNTO 0)(
+                    g_NUM_BIQUADS-1 DOWNTO 0)(
                     b0(g_COEFF_INT_WIDTH-1 DOWNTO -g_COEFF_FRAC_WIDTH),
                     b1(g_COEFF_INT_WIDTH-1 DOWNTO -g_COEFF_FRAC_WIDTH),
                     b2(g_COEFF_INT_WIDTH-1 DOWNTO -g_COEFF_FRAC_WIDTH),
@@ -187,47 +187,54 @@ BEGIN
     --     RAM address 7 + 8*{biquad_idx} = unused
     FOR ch IN 0 TO g_CHANNELS-1
     LOOP
-      CASE coeff_idx IS
-        WHEN 0 =>
-          wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
-            (to_slv(coeffs(ch)(biquad_idx).b0), OTHERS => '0');
-        WHEN 1 =>
-          wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
-            (to_slv(coeffs(ch)(biquad_idx).b1), OTHERS => '0');
-        WHEN 2 =>
-          wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
-            (to_slv(coeffs(ch)(biquad_idx).b2), OTHERS => '0');
-        WHEN 3 =>
-          wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
-            (to_slv(coeffs(ch)(biquad_idx).a1), OTHERS => '0');
-        WHEN 4 =>
-          wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
-            (to_slv(coeffs(ch)(biquad_idx).a2), OTHERS => '0');
-        WHEN OTHERS =>
-      END CASE;
+      IF biquad_idx < g_NUM_BIQUADS THEN
+        CASE coeff_idx IS
+          WHEN 0 =>
+            wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
+              (to_slv(coeffs(ch)(biquad_idx).b0), OTHERS => '0');
+          WHEN 1 =>
+            wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
+              (to_slv(coeffs(ch)(biquad_idx).b1), OTHERS => '0');
+          WHEN 2 =>
+            wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
+              (to_slv(coeffs(ch)(biquad_idx).b2), OTHERS => '0');
+          WHEN 3 =>
+            wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
+              (to_slv(coeffs(ch)(biquad_idx).a1), OTHERS => '0');
+          WHEN 4 =>
+            wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <=
+              (to_slv(coeffs(ch)(biquad_idx).a2), OTHERS => '0');
+          WHEN OTHERS =>
+        END CASE;
+      -- If trying to access biquads that aren't instatiated, return zeros
+      ELSE
+        wb_fofb_shaper_filt_regs_coeffs_i_ifc_arr(ch).data <= (OTHERS => '0');
+      END IF;
 
       IF rising_edge(clk_i) THEN
         IF rst_n_i = '0' THEN
         ELSE
           IF wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).wr = '1' THEN
-            CASE coeff_idx IS
-              WHEN 0 =>
-                coeffs(ch)(biquad_idx).b0 <= f_parse_wb_coeff(
-                  wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
-              WHEN 1 =>
-                coeffs(ch)(biquad_idx).b1 <= f_parse_wb_coeff(
-                  wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
-              WHEN 2 =>
-                coeffs(ch)(biquad_idx).b2 <= f_parse_wb_coeff(
-                  wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
-              WHEN 3 =>
-                coeffs(ch)(biquad_idx).a1 <= f_parse_wb_coeff(
-                  wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
-              WHEN 4 =>
-                coeffs(ch)(biquad_idx).a2 <= f_parse_wb_coeff(
-                  wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
-              WHEN OTHERS =>
-            END CASE;
+            IF biquad_idx < g_NUM_BIQUADS THEN
+              CASE coeff_idx IS
+                WHEN 0 =>
+                  coeffs(ch)(biquad_idx).b0 <= f_parse_wb_coeff(
+                    wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
+                WHEN 1 =>
+                  coeffs(ch)(biquad_idx).b1 <= f_parse_wb_coeff(
+                    wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
+                WHEN 2 =>
+                  coeffs(ch)(biquad_idx).b2 <= f_parse_wb_coeff(
+                    wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
+                WHEN 3 =>
+                  coeffs(ch)(biquad_idx).a1 <= f_parse_wb_coeff(
+                    wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
+                WHEN 4 =>
+                  coeffs(ch)(biquad_idx).a2 <= f_parse_wb_coeff(
+                    wb_fofb_shaper_filt_regs_coeffs_o_ifc_arr(ch).data);
+                WHEN OTHERS =>
+              END CASE;
+            END IF;
           END IF;
         END IF;
       END IF;
diff --git a/hdl/testbench/xwb_fofb_shaper_filt/fofb_shaper_filt_coeffs.dat b/hdl/testbench/xwb_fofb_shaper_filt/fofb_shaper_filt_coeffs.dat
index fed8075..7b6090a 100644
--- a/hdl/testbench/xwb_fofb_shaper_filt/fofb_shaper_filt_coeffs.dat
+++ b/hdl/testbench/xwb_fofb_shaper_filt/fofb_shaper_filt_coeffs.dat
@@ -1,12 +1,12 @@
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+9.26728558e-03 1.85345712e-02 9.26728558e-03 -1.38777878e-16 9.70055654e-03 1.00000000e+00 2.00000000e+00 1.00000000e+00 -1.94289029e-16 9.20192105e-02 1.00000000e+00 2.00000000e+00 1.00000000e+00 -1.66533454e-16 2.85702154e-01 1.00000000e+00 2.00000000e+00 1.00000000e+00 -2.22044605e-16 6.73513678e-01 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0
+9.26728558e-03 1.85345712e-02 9.26728558e-03 -1.38777878e-16 9.70055654e-03 1.00000000e+00 2.00000000e+00 1.00000000e+00 -1.94289029e-16 9.20192105e-02 1.00000000e+00 2.00000000e+00 1.00000000e+00 -1.66533454e-16 2.85702154e-01 1.00000000e+00 2.00000000e+00 1.00000000e+00 -2.22044605e-16 6.73513678e-01 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0
+9.26728558e-03 1.85345712e-02 9.26728558e-03 -1.38777878e-16 9.70055654e-03 1.00000000e+00 2.00000000e+00 1.00000000e+00 -1.94289029e-16 9.20192105e-02 1.00000000e+00 2.00000000e+00 1.00000000e+00 -1.66533454e-16 2.85702154e-01 1.00000000e+00 2.00000000e+00 1.00000000e+00 -2.22044605e-16 6.73513678e-01 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0
diff --git a/hdl/testbench/xwb_fofb_shaper_filt/xwb_fofb_shaper_filt_tb.vhd b/hdl/testbench/xwb_fofb_shaper_filt/xwb_fofb_shaper_filt_tb.vhd
index a25759a..0f8ecc9 100644
--- a/hdl/testbench/xwb_fofb_shaper_filt/xwb_fofb_shaper_filt_tb.vhd
+++ b/hdl/testbench/xwb_fofb_shaper_filt/xwb_fofb_shaper_filt_tb.vhd
@@ -176,6 +176,12 @@ BEGIN
           -- Read back filter coefficients
           read32_pl(clk, wb_slave_i, wb_slave_o, v_wb_addr, v_wb_dat);
 
+          -- If trying to access a non-instatiated biquad, the expected return
+          -- value for the coefficients is 0
+          IF biquad_idx >= g_NUM_BIQUADS THEN
+            v_wb_coeff := x"00000000";
+          END IF;
+
           ASSERT v_wb_dat = v_wb_coeff
             REPORT
               "UNEXPECTED FILTER COEFFICIENT "