From 44ef1a541c44b0f47a73ac106d208cf3e4f5e132 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joachim=20Stro=CC=88mbergson?= <joachim@secworks.se>
Date: Fri, 27 Apr 2018 10:11:46 +0200
Subject: Removed redundant FSM from the W memory.

---
 src/rtl/sha1_w_mem.v   | 71 +++++++-------------------------------------------
 src/tb/tb_sha1_w_mem.v |  4 +--
 2 files changed, 11 insertions(+), 64 deletions(-)

diff --git a/src/rtl/sha1_w_mem.v b/src/rtl/sha1_w_mem.v
index f50741e..2ba80f5 100644
--- a/src/rtl/sha1_w_mem.v
+++ b/src/rtl/sha1_w_mem.v
@@ -86,12 +86,6 @@ module sha1_w_mem(
   reg [6 : 0] w_ctr_reg;
   reg [6 : 0] w_ctr_new;
   reg         w_ctr_we;
-  reg         w_ctr_inc;
-  reg         w_ctr_rst;
-
-  reg         sha1_w_mem_ctrl_reg;
-  reg         sha1_w_mem_ctrl_new;
-  reg         sha1_w_mem_ctrl_we;
 
 
   //----------------------------------------------------------------
@@ -123,7 +117,7 @@ module sha1_w_mem(
           for (i = 0 ; i < 16 ; i = i + 1)
             w_mem[i] <= 32'h0;
 
-          sha1_w_mem_ctrl_reg <= CTRL_IDLE;
+          w_ctr_reg <= 7'h0;
         end
       else
         begin
@@ -149,9 +143,6 @@ module sha1_w_mem(
 
           if (w_ctr_we)
             w_ctr_reg <= w_ctr_new;
-
-          if (sha1_w_mem_ctrl_we)
-            sha1_w_mem_ctrl_reg <= sha1_w_mem_ctrl_new;
         end
     end // reg_update
 
@@ -165,13 +156,9 @@ module sha1_w_mem(
   always @*
     begin : select_w
       if (w_ctr_reg < 16)
-        begin
-          w_tmp = w_mem[w_ctr_reg[3 : 0]];
-        end
+        w_tmp = w_mem[w_ctr_reg[3 : 0]];
       else
-        begin
-          w_tmp = w_new;
-        end
+        w_tmp = w_new;
     end // select_w
 
 
@@ -235,7 +222,7 @@ module sha1_w_mem(
           w_mem_we    = 1;
         end
 
-      else if (w_ctr_reg > 15)
+      if (next && (w_ctr_reg > 15))
         begin
           w_mem00_new = w_mem[01];
           w_mem01_new = w_mem[02];
@@ -267,60 +254,20 @@ module sha1_w_mem(
   always @*
     begin : w_ctr
       w_ctr_new = 7'h0;
-      w_ctr_we  = 0;
+      w_ctr_we  = 1'h0;
 
-      if (w_ctr_rst)
+      if (init)
         begin
           w_ctr_new = 7'h0;
-          w_ctr_we  = 1;
+          w_ctr_we  = 1'h1;
         end
 
-      if (w_ctr_inc)
+      if (next)
         begin
           w_ctr_new = w_ctr_reg + 7'h01;
-          w_ctr_we  = 1;
+          w_ctr_we  = 1'h1;
         end
     end // w_ctr
-
-
-  //----------------------------------------------------------------
-  // sha1_w_mem_fsm
-  //
-  // Logic for the w shedule FSM.
-  //----------------------------------------------------------------
-  always @*
-    begin : sha1_w_mem_fsm
-      w_ctr_rst           = 0;
-      w_ctr_inc           = 0;
-      sha1_w_mem_ctrl_new = CTRL_IDLE;
-      sha1_w_mem_ctrl_we  = 0;
-
-      case (sha1_w_mem_ctrl_reg)
-        CTRL_IDLE:
-          begin
-            if (init)
-              begin
-                w_ctr_rst           = 1;
-                sha1_w_mem_ctrl_new = CTRL_UPDATE;
-                sha1_w_mem_ctrl_we  = 1;
-              end
-          end
-
-        CTRL_UPDATE:
-          begin
-            if (next)
-              begin
-                w_ctr_inc = 1;
-              end
-
-            if (w_ctr_reg == SHA1_ROUNDS)
-              begin
-                sha1_w_mem_ctrl_new = CTRL_IDLE;
-                sha1_w_mem_ctrl_we  = 1;
-              end
-          end
-      endcase // case (sha1_ctrl_reg)
-    end // sha1_w_mem_fsm
 endmodule // sha1_w_mem
 
 //======================================================================
diff --git a/src/tb/tb_sha1_w_mem.v b/src/tb/tb_sha1_w_mem.v
index 1ee018f..2d19525 100644
--- a/src/tb/tb_sha1_w_mem.v
+++ b/src/tb/tb_sha1_w_mem.v
@@ -128,8 +128,8 @@ module tb_sha1_w_mem();
       $display("W state:");
 
 
-      $display("ctrl_reg = %01x, w_ctr_reg = %02x, init = %01x, next = %01x",
-               dut.sha1_w_mem_ctrl_reg, dut.w_ctr_reg, dut.init, dut.next);
+      $display("w_ctr_reg = %02x, init = %01x, next = %01x",
+               dut.w_ctr_reg, dut.init, dut.next);
 
       $display("w_tmp   = %08x, w_new   = %08x", dut.w_tmp, dut.w_new);
 
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