[es/csrng/edn] Don't clear packer FIFOs upon read

Previously, all packer FIFOs in the entropy complex where by default
cleared to zero upon read. However, as this may simplify attacks trying
to manipulate the random number distribution it should better be
avoided. Leaving around the previous random data on the bus/wires after
the read is preferred over outputting a deterministic value in this
case.

Signed-off-by: Pirmin Vogel <vogelpi@lowrisc.org>
Signed-off-by: Michael Schaffner <msf@opentitan.org>

hw/ip/csrng/rtl/csrng_core.sv

diff --git a/hw/ip/csrng/rtl/csrng_core.sv b/hw/ip/csrng/rtl/csrng_core.sv
index f36dcbb..61362b9 100644
--- a/hw/ip/csrng/rtl/csrng_core.sv
+++ b/hw/ip/csrng/rtl/csrng_core.sv
@@ -795,7 +795,8 @@
 
   prim_packer_fifo #(
     .InW(BlkLen),
-    .OutW(32)
+    .OutW(32),
+    .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_sw_genbits (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),
@@ -989,7 +990,8 @@
 
   prim_packer_fifo #(
     .InW(32),
-    .OutW(SeedLen)
+    .OutW(SeedLen),
+    .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_adata (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),

hw/ip/edn/rtl/edn_core.sv

diff --git a/hw/ip/edn/rtl/edn_core.sv b/hw/ip/edn/rtl/edn_core.sv
index 17b284c..ff68865 100644
--- a/hw/ip/edn/rtl/edn_core.sv
+++ b/hw/ip/edn/rtl/edn_core.sv
@@ -615,7 +615,8 @@
 
   prim_packer_fifo #(
      .InW(CSGenBitsWidth),
-     .OutW(CSGenBitsWidth)
+     .OutW(CSGenBitsWidth),
+     .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_cs (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),
@@ -675,7 +676,8 @@
 
     prim_packer_fifo #(
       .InW(CSGenBitsWidth),
-      .OutW(EndPointBusWidth)
+      .OutW(EndPointBusWidth),
+      .ClearOnRead(1'b0)
     ) u_prim_packer_fifo_ep (
       .clk_i      (clk_i),
       .rst_ni     (rst_ni),

hw/ip/entropy_src/rtl/entropy_src_core.sv

diff --git a/hw/ip/entropy_src/rtl/entropy_src_core.sv b/hw/ip/entropy_src/rtl/entropy_src_core.sv
index 7da5d52..4951a18 100644
--- a/hw/ip/entropy_src/rtl/entropy_src_core.sv
+++ b/hw/ip/entropy_src/rtl/entropy_src_core.sv
@@ -720,7 +720,8 @@
 
   prim_packer_fifo #(
     .InW(1),
-    .OutW(RngBusWidth)
+    .OutW(RngBusWidth),
+    .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_esbit (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),
@@ -1915,7 +1916,8 @@
 
   prim_packer_fifo #(
     .InW(RngBusWidth),
-    .OutW(PostHTWidth)
+    .OutW(PostHTWidth),
+    .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_postht (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),
@@ -1987,7 +1989,8 @@
 
   prim_packer_fifo #(
     .InW(ObserveFifoWidth),
-    .OutW(PreCondWidth)
+    .OutW(PreCondWidth),
+    .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_precon (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),
@@ -2086,7 +2089,8 @@
 
   prim_packer_fifo #(
      .InW(PreCondWidth),
-     .OutW(SeedLen)
+     .OutW(SeedLen),
+     .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_bypass (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),
@@ -2232,7 +2236,8 @@
 
   prim_packer_fifo #(
     .InW(SeedLen),
-    .OutW(FullRegWidth)
+    .OutW(FullRegWidth),
+    .ClearOnRead(1'b0)
   ) u_prim_packer_fifo_swread (
     .clk_i      (clk_i),
     .rst_ni     (rst_ni),