From 8bdf1eaf0ff07d5c34fa142a9343e50badc8c2d8 Mon Sep 17 00:00:00 2001
From: David Harris <david_harris@hmc.edu>
Date: Sat, 17 Jul 2021 21:15:08 -0400
Subject: [PATCH] added lrsc.sv

---
 wally-pipelined/src/lsu/lrsc.sv | 64 +++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 wally-pipelined/src/lsu/lrsc.sv

diff --git a/wally-pipelined/src/lsu/lrsc.sv b/wally-pipelined/src/lsu/lrsc.sv
new file mode 100644
index 00000000..44f2ef7d
--- /dev/null
+++ b/wally-pipelined/src/lsu/lrsc.sv
@@ -0,0 +1,64 @@
+///////////////////////////////////////////
+// lrsc.sv
+//
+// Written: David_Harris@hmc.edu 17 July 2021
+// Modified: 
+//
+// Purpose: Load Reserved / Store Conditional unit
+//          Track the reservation and squash the store if it fails
+// 
+// A component of the Wally configurable RISC-V project.
+// 
+// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, 
+// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
+// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT 
+// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+///////////////////////////////////////////
+
+`include "wally-config.vh"
+
+module lrsc
+  (
+    input  logic                clk, reset,
+    input  logic                FlushW, StallWtoDCache,
+    input  logic                MemReadM,
+    input  logic [1:0]          MemRWMtoDCache, // *** how does this differ from MemReadM
+    input  logic [1:0] 		    AtomicMtoDCache,
+    input  logic [`PA_BITS-1:0] MemPAdrM,  // from mmu to dcache
+    output logic                SquashSCM,
+    output logic                SquashSCWfromDCache
+);
+  // Handle atomic load reserved / store conditional
+  generate
+    if (`A_SUPPORTED) begin // atomic instructions supported
+      logic [`PA_BITS-1:2]  ReservationPAdrW;
+      logic 		            ReservationValidM, ReservationValidW; 
+      logic 		            lrM, scM, WriteAdrMatchM;
+
+      assign lrM = MemReadM && AtomicMtoDCache[0];
+      assign scM = MemRWMtoDCache[0] && AtomicMtoDCache[0]; 
+      assign WriteAdrMatchM = MemRWMtoDCache[0] && (MemPAdrM[`PA_BITS-1:2] == ReservationPAdrW) && ReservationValidW;
+      assign SquashSCM = scM && ~WriteAdrMatchM;
+      always_comb begin // ReservationValidM (next value of valid reservation)
+        if (lrM) ReservationValidM = 1;  // set valid on load reserve
+        else if (scM || WriteAdrMatchM) ReservationValidM = 0; // clear valid on store to same address or any sc
+        else ReservationValidM = ReservationValidW; // otherwise don't change valid
+      end
+      flopenrc #(`PA_BITS-2) resadrreg(clk, reset, FlushW, lrM, MemPAdrM[`PA_BITS-1:2], ReservationPAdrW); // could drop clear on this one but not valid
+      flopenrc #(1) resvldreg(clk, reset, FlushW, lrM, ReservationValidM, ReservationValidW);
+      flopenrc #(1) squashreg(clk, reset, FlushW, ~StallWtoDCache, SquashSCM, SquashSCWfromDCache);
+    end else begin // Atomic operations not supported
+      assign SquashSCM = 0;
+      assign SquashSCWfromDCache = 0; 
+    end
+  endgenerate
+endmodule
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