From a514554eeb4cd6cf4eaef7a92c62ef351bea7b36 Mon Sep 17 00:00:00 2001
From: David Harris <david_harris@hmc.edu>
Date: Wed, 23 Jun 2021 03:03:52 -0400
Subject: [PATCH] Reduced complexity of pmpadrdec

---
 .../regression/wave-dos/peripheral-waves.do   | 22 +++++++++----------
 wally-pipelined/src/mmu/pmpadrdec.sv          |  2 +-
 wally-pipelined/src/mmu/pmpchecker.sv         |  4 ++++
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/wally-pipelined/regression/wave-dos/peripheral-waves.do b/wally-pipelined/regression/wave-dos/peripheral-waves.do
index 5c9f3870..1304b40c 100644
--- a/wally-pipelined/regression/wave-dos/peripheral-waves.do
+++ b/wally-pipelined/regression/wave-dos/peripheral-waves.do
@@ -65,17 +65,17 @@ add wave -hex /testbench/dut/hart/priv/csr/genblk1/csrm/MEPC_REGW
 add wave -divider
 
 # peripherals
-add wave -hex /testbench/dut/uncore/plic/*
-add wave -hex /testbench/dut/uncore/plic/intPriority
-add wave -hex /testbench/dut/uncore/plic/pendingArray
-add wave -divider
-add wave -hex /testbench/dut/uncore/uart/u/*
-add wave -divider
-add wave -hex /testbench/dut/uncore/gpio/*
-add wave -divider
-add wave -hex /testbench/dut/hart/ebu/*
-add wave -divider
-add wave -divider
+#add wave -hex /testbench/dut/uncore/plic/*
+#add wave -hex /testbench/dut/uncore/plic/intPriority
+#add wave -hex /testbench/dut/uncore/plic/pendingArray
+#add wave -divider
+#add wave -hex /testbench/dut/uncore/uart/u/*
+#add wave -divider
+#add wave -hex /testbench/dut/uncore/gpio/*
+#add wave -divider
+#add wave -hex /testbench/dut/hart/ebu/*
+#add wave -divider
+#add wave -divider
 
 # everything else
 add wave -hex -r /testbench/*
diff --git a/wally-pipelined/src/mmu/pmpadrdec.sv b/wally-pipelined/src/mmu/pmpadrdec.sv
index 11c239b2..87f5d8f1 100644
--- a/wally-pipelined/src/mmu/pmpadrdec.sv
+++ b/wally-pipelined/src/mmu/pmpadrdec.sv
@@ -67,7 +67,7 @@ module pmpadrdec (
   // create a mask of which bits to ignore
   generate
     assign Mask[1:0] = 2'b11;
-    assign Mask[2] = ~CurrentPMPAdr[0] & (AdrMode == NAPOT); // mask has 0s in upper bis for NA4 region
+    assign Mask[2] = (AdrMode == NAPOT); // mask has 0s in upper bis for NA4 region
     for (i=3; i < `PA_BITS; i=i+1) 
       assign Mask[i] = Mask[i-1] & CurrentPMPAdr[i-3]; // NAPOT mask: 1's indicate bits to ignore
    endgenerate
diff --git a/wally-pipelined/src/mmu/pmpchecker.sv b/wally-pipelined/src/mmu/pmpchecker.sv
index 8b33ccf3..f88d56fa 100644
--- a/wally-pipelined/src/mmu/pmpchecker.sv
+++ b/wally-pipelined/src/mmu/pmpchecker.sv
@@ -76,6 +76,8 @@ module pmpchecker (
   logic L_Bit, X_Bit, W_Bit, R_Bit;
   logic InvalidExecute, InvalidWrite, InvalidRead;
 
+  // *** extend to optionally 64 configurations
+
   assign {PMPCFG[15], PMPCFG[14], PMPCFG[13], PMPCFG[12],
           PMPCFG[11], PMPCFG[10], PMPCFG[9], PMPCFG[8]} = PMPCFG23_REGW;
 
@@ -107,6 +109,7 @@ module pmpchecker (
   // Only enforce PMP checking for S and U modes when at least one PMP is active
   assign EnforcePMP = |ActiveRegion;
 
+  // *** extend to up to 64, fold bit extraction to avoid need for binary encoding of region
   always_comb
     casez (Regions)
       16'b???????????????1: MatchedRegion = 0;
@@ -137,6 +140,7 @@ module pmpchecker (
   assign InvalidWrite   = WriteAccessM   && ~W_Bit;
   assign InvalidRead    = ReadAccessM    && ~R_Bit;
 
+  // *** don't cause faults when there are no PMPs
   assign PMPInstrAccessFaultF = (PrivilegeModeW == `M_MODE) ?
                                   Match && L_Bit && InvalidExecute :
                                   EnforcePMP && InvalidExecute;