From be6468c6d94370d5623b62e457baf7888129a06c Mon Sep 17 00:00:00 2001
From: Ross Thompson <stephen.thompson.37@us.af.mil>
Date: Wed, 30 Jun 2021 19:24:59 -0500
Subject: [PATCH] Icache ITLB interlock fix.

---
 wally-pipelined/src/cache/ICacheCntrl.sv | 26 ++++++++++++++++++++----
 wally-pipelined/src/cache/icache.sv      | 21 +++++++++++--------
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/wally-pipelined/src/cache/ICacheCntrl.sv b/wally-pipelined/src/cache/ICacheCntrl.sv
index f290f0ad2..bc5c30b3b 100644
--- a/wally-pipelined/src/cache/ICacheCntrl.sv
+++ b/wally-pipelined/src/cache/ICacheCntrl.sv
@@ -40,8 +40,8 @@ module ICacheCntrl #(parameter BLOCKLEN = 256) (
     input logic [31:0] 		ICacheMemReadData,
     input logic 		ICacheMemReadValid,
     // The address at which we want to search the cache memory
-    output logic [`PA_BITS-1:0] 	PCTagF,
-    output logic [`PA_BITS-1:0]    PCNextIndexF,						     
+    output logic [`PA_BITS-1:0] PCTagF,
+    output logic [`PA_BITS-1:0] PCNextIndexF, 
     output logic 		ICacheReadEn,
     // Load data into the cache
     output logic 		ICacheMemWriteEnable,
@@ -56,13 +56,15 @@ module ICacheCntrl #(parameter BLOCKLEN = 256) (
 
     // Outputs to pipeline control stuff
     output logic 		ICacheStallF, EndFetchState,
+    input logic  ITLBMissF,
+    input logic  ITLBWriteF,
 
     // Signals to/from ahblite interface
     // A read containing the requested data
     input logic [`XLEN-1:0] 	InstrInF,
     input logic 		InstrAckF,
     // The read we request from main memory
-    output logic [`PA_BITS-1:0]	InstrPAdrF,
+    output logic [`PA_BITS-1:0] InstrPAdrF,
     output logic 		InstrReadF
 );
 
@@ -109,6 +111,10 @@ module ICacheCntrl #(parameter BLOCKLEN = 256) (
   
 
   localparam STATE_INVALIDATE = 18; // *** not sure if invalidate or evict? invalidate by cache block or address?
+  localparam STATE_TLB_MISS = 19;
+  localparam STATE_TLB_MISS_DONE = 20;
+  
+  
   
   localparam AHBByteLength = `XLEN / 8;
   localparam AHBOFFETWIDTH = $clog2(AHBByteLength);
@@ -209,7 +215,9 @@ module ICacheCntrl #(parameter BLOCKLEN = 256) (
       STATE_READY: begin
 	PCMux = 2'b00;
 	ICacheReadEn = 1'b1;
-	if (hit & ~spill) begin
+	if (ITLBMissF) begin
+	  NextState = STATE_TLB_MISS;
+	end else if (hit & ~spill) begin
 	  SavePC = 1'b1;
 	  ICacheStallF = 1'b0;
 	  NextState = STATE_READY;
@@ -363,6 +371,16 @@ module ICacheCntrl #(parameter BLOCKLEN = 256) (
 	ICacheStallF = 1'b0;	
 	NextState = STATE_READY;
       end
+      STATE_TLB_MISS: begin
+	if (ITLBWriteF) begin
+	  NextState = STATE_TLB_MISS_DONE;
+	end else begin
+	  NextState = STATE_TLB_MISS;
+	end
+      end
+      STATE_TLB_MISS_DONE : begin
+	NextState = STATE_READY;
+      end
       default: begin
 	PCMux = 2'b01;
 	NextState = STATE_READY;
diff --git a/wally-pipelined/src/cache/icache.sv b/wally-pipelined/src/cache/icache.sv
index abf828fc5..89b2ff9e7 100644
--- a/wally-pipelined/src/cache/icache.sv
+++ b/wally-pipelined/src/cache/icache.sv
@@ -28,24 +28,27 @@
 module icache
   (
    // Basic pipeline stuff
-   input logic 		    clk, reset,
-   input logic 		    StallF, StallD,
-   input logic 		    FlushD,
+   input logic 		       clk, reset,
+   input logic 		       StallF, StallD,
+   input logic 		       FlushD,
    input logic [`PA_BITS-1:0]  PCNextF,
    input logic [`PA_BITS-1:0]  PCPF, 
    // Data read in from the ebu unit
-   input logic [`XLEN-1:0]  InstrInF,
-   input logic 		    InstrAckF,
+   input logic [`XLEN-1:0]     InstrInF,
+   input logic 		       InstrAckF,
    // Read requested from the ebu unit
    output logic [`PA_BITS-1:0] InstrPAdrF,
-   output logic 	    InstrReadF,
+   output logic 	       InstrReadF,
    // High if the instruction currently in the fetch stage is compressed
-   output logic 	    CompressedF,
+   output logic 	       CompressedF,
    // High if the icache is requesting a stall
-   output logic 	    ICacheStallF,
+   output logic 	       ICacheStallF,
+   input logic 		       ITLBMissF,
+   input logic 		       ITLBWriteF,
+   
    // The raw (not decompressed) instruction that was requested
    // If this instruction is compressed, upper 16 bits may be the next 16 bits or may be zeros
-   output logic [31:0] 	    FinalInstrRawF
+   output logic [31:0] 	       FinalInstrRawF
    );
 
   // Configuration parameters