From 8a8f05fad0bb91dc991a60785da5c49db565de00 Mon Sep 17 00:00:00 2001
From: Michael Schaffner <msf@opentitan.org>
Date: Wed, 17 Jan 2024 16:13:28 -0800
Subject: [PATCH] [icache] Disable S&P diffusion layer in memory scrambling

Signed-off-by: Michael Schaffner <msf@opentitan.org>
---
 dv/uvm/icache/dv/tb/tb.sv | 9 ++-------
 rtl/ibex_top.sv           | 9 ++-------
 2 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/dv/uvm/icache/dv/tb/tb.sv b/dv/uvm/icache/dv/tb/tb.sv
index dcf99e1980..9848cc8ec0 100644
--- a/dv/uvm/icache/dv/tb/tb.sv
+++ b/dv/uvm/icache/dv/tb/tb.sv
@@ -32,7 +32,6 @@ module tb #(
   localparam int unsigned LineSizeECC = BusSizeECC * IC_LINE_BEATS;
   localparam int unsigned TagSizeECC  = ICacheECC ? (IC_TAG_SIZE + 6) : IC_TAG_SIZE;
   localparam int unsigned NumAddrScrRounds  = 2;
-  localparam int unsigned NumDiffRounds     = NumAddrScrRounds;
 
   ibex_icache_ram_if #(
     .TagSizeECC(TagSizeECC),
@@ -137,9 +136,7 @@ module tb #(
       .Depth            (IC_NUM_LINES),
       .DataBitsPerMask  (TagSizeECC),
       .EnableParity     (0),
-      .DiffWidth        (TagSizeECC),
-      .NumAddrScrRounds (NumAddrScrRounds),
-      .NumDiffRounds    (NumDiffRounds)
+      .NumAddrScrRounds (NumAddrScrRounds)
     ) tag_bank (
       .clk_i       (clk),
       .rst_ni      (rst_n),
@@ -171,9 +168,7 @@ module tb #(
       .DataBitsPerMask    (LineSizeECC),
       .EnableParity       (0),
       .ReplicateKeyStream (1),
-      .DiffWidth          (LineSizeECC),
-      .NumAddrScrRounds   (NumAddrScrRounds),
-      .NumDiffRounds      (NumDiffRounds)
+      .NumAddrScrRounds   (NumAddrScrRounds)
     ) data_bank (
       .clk_i       (clk),
       .rst_ni      (rst_n),
diff --git a/rtl/ibex_top.sv b/rtl/ibex_top.sv
index dff77b0cde..66992ccd0d 100644
--- a/rtl/ibex_top.sv
+++ b/rtl/ibex_top.sv
@@ -155,7 +155,6 @@ module ibex_top import ibex_pkg::*; #(
   localparam int unsigned TagSizeECC        = ICacheECC ? (IC_TAG_SIZE + 6) : IC_TAG_SIZE;
   // Scrambling Parameter
   localparam int unsigned NumAddrScrRounds  = ICacheScramble ? 2 : 0;
-  localparam int unsigned NumDiffRounds     = NumAddrScrRounds;
 
   // Clock signals
   logic                        clk;
@@ -565,9 +564,7 @@ module ibex_top import ibex_pkg::*; #(
           .Depth            (IC_NUM_LINES),
           .DataBitsPerMask  (TagSizeECC),
           .EnableParity     (0),
-          .DiffWidth        (TagSizeECC),
-          .NumAddrScrRounds (NumAddrScrRounds),
-          .NumDiffRounds    (NumDiffRounds)
+          .NumAddrScrRounds (NumAddrScrRounds)
         ) tag_bank (
           .clk_i,
           .rst_ni,
@@ -599,9 +596,7 @@ module ibex_top import ibex_pkg::*; #(
           .DataBitsPerMask    (LineSizeECC),
           .ReplicateKeyStream (1),
           .EnableParity       (0),
-          .DiffWidth          (LineSizeECC),
-          .NumAddrScrRounds   (NumAddrScrRounds),
-          .NumDiffRounds      (NumDiffRounds)
+          .NumAddrScrRounds   (NumAddrScrRounds)
         ) data_bank (
           .clk_i,
           .rst_ni,