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Added buscachefsm for system with bus and cache

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David Harris 2022-08-25 18:01:01 -07:00
parent 5340c45dfc
commit 69dff87feb
3 changed files with 194 additions and 2 deletions
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192
pipelined/src/lsu/buscachefsm.sv Normal file
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@ -0,0 +1,192 @@
///////////////////////////////////////////
// busfsm.sv
//
// Written: Ross Thompson ross1728@gmail.com December 29, 2021
// Modified:
//
// Purpose: Load/Store Unit's interface to BUS for cache-based system
//
// A component of the Wally configurable RISC-V project.
//
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// MIT LICENSE
// 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 buscachefsm #(parameter integer WordCountThreshold,
parameter integer LOGWPL, parameter logic CACHE_ENABLED )
(input logic clk,
input logic reset,
input logic IgnoreRequest,
input logic [1:0] RW,
input logic CacheFetchLine,
input logic CacheWriteLine,
input logic BusAck,
input logic BusInit, // This might be better as LSUBusLock, or to send this using BusAck.
input logic CPUBusy,
input logic Cacheable,
output logic BusStall,
output logic BusWrite,
output logic SelBusWord,
output logic BusRead,
output logic [2:0] HBURST,
output logic BusTransComplete,
output logic [1:0] HTRANS,
output logic CacheBusAck,
output logic BusCommitted,
output logic SelUncachedAdr,
output logic BufferCaptureEn,
output logic [LOGWPL-1:0] WordCount, WordCountDelayed);
logic UnCachedBusRead;
logic UnCachedBusWrite;
logic CntEn, PreCntEn;
logic CntReset;
logic WordCountFlag;
logic [LOGWPL-1:0] NextWordCount;
logic UnCachedAccess, UnCachedRW;
logic [2:0] LocalBurstType;
typedef enum logic [2:0] {STATE_BUS_READY,
STATE_BUS_FETCH,
STATE_BUS_WRITE,
STATE_BUS_UNCACHED_WRITE,
STATE_BUS_UNCACHED_WRITE_DONE,
STATE_BUS_UNCACHED_READ,
STATE_BUS_UNCACHED_READ_DONE,
STATE_BUS_CPU_BUSY} busstatetype;
typedef enum logic [1:0] {AHB_IDLE = 2'b00, AHB_BUSY = 2'b01, AHB_NONSEQ = 2'b10, AHB_SEQ = 2'b11} ahbtranstype;
(* mark_debug = "true" *) busstatetype BusCurrState, BusNextState;
// Used to send address for address stage of AHB.
flopenr #(LOGWPL)
WordCountReg(.clk(clk),
.reset(reset | CntReset),
.en(CntEn),
.d(NextWordCount),
.q(WordCount));
// Used to store data from data phase of AHB.
flopenr #(LOGWPL)
WordCountDelayedReg(.clk(clk),
.reset(reset | CntReset),
.en(CntEn),
.d(WordCount),
.q(WordCountDelayed));
assign NextWordCount = WordCount + 1'b1;
assign PreCntEn = (BusCurrState == STATE_BUS_FETCH) | (BusCurrState == STATE_BUS_WRITE);
assign WordCountFlag = (WordCountDelayed == WordCountThreshold[LOGWPL-1:0]); // Detect when we are waiting on the final access.
assign CntEn = (PreCntEn & BusAck | BusInit) & ~WordCountFlag & ~UnCachedRW; // Want to count when doing cache accesses and we aren't wrapping up.
assign UnCachedAccess = ~CACHE_ENABLED | ~Cacheable;
always_ff @(posedge clk)
if (reset) BusCurrState <= #1 STATE_BUS_READY;
else BusCurrState <= #1 BusNextState;
always_comb begin
case(BusCurrState)
STATE_BUS_READY: if(IgnoreRequest) BusNextState = STATE_BUS_READY;
else if(RW[0] & UnCachedAccess) BusNextState = STATE_BUS_UNCACHED_WRITE;
else if(RW[1] & UnCachedAccess) BusNextState = STATE_BUS_UNCACHED_READ;
else if(CacheFetchLine) BusNextState = STATE_BUS_FETCH;
else if(CacheWriteLine) BusNextState = STATE_BUS_WRITE;
else BusNextState = STATE_BUS_READY;
STATE_BUS_UNCACHED_WRITE: if(BusAck) BusNextState = STATE_BUS_UNCACHED_WRITE_DONE;
else BusNextState = STATE_BUS_UNCACHED_WRITE;
STATE_BUS_UNCACHED_READ: if(BusAck) BusNextState = STATE_BUS_UNCACHED_READ_DONE;
else BusNextState = STATE_BUS_UNCACHED_READ;
STATE_BUS_UNCACHED_WRITE_DONE: if(CPUBusy) BusNextState = STATE_BUS_CPU_BUSY;
else BusNextState = STATE_BUS_READY;
STATE_BUS_UNCACHED_READ_DONE: if(CPUBusy) BusNextState = STATE_BUS_CPU_BUSY;
else BusNextState = STATE_BUS_READY;
STATE_BUS_CPU_BUSY: if(CPUBusy) BusNextState = STATE_BUS_CPU_BUSY;
else BusNextState = STATE_BUS_READY;
STATE_BUS_FETCH: if (WordCountFlag & BusAck) begin
if (CacheFetchLine) BusNextState = STATE_BUS_FETCH;
else if (CacheWriteLine) BusNextState = STATE_BUS_WRITE;
else BusNextState = STATE_BUS_READY;
end else BusNextState = STATE_BUS_FETCH;
STATE_BUS_WRITE: if(WordCountFlag & BusAck) begin
if (CacheFetchLine) BusNextState = STATE_BUS_FETCH;
else if (CacheWriteLine) BusNextState = STATE_BUS_WRITE;
else BusNextState = STATE_BUS_READY;
end else BusNextState = STATE_BUS_WRITE;
default: BusNextState = STATE_BUS_READY;
endcase
end
always_comb begin
case(WordCountThreshold)
0: LocalBurstType = 3'b000;
3: LocalBurstType = 3'b011; // INCR4
7: LocalBurstType = 3'b101; // INCR8
15: LocalBurstType = 3'b111; // INCR16
default: LocalBurstType = 3'b001; // INCR without end.
endcase
end
assign HBURST = (UnCachedRW) ? 3'b0 : LocalBurstType; // Don't want to use burst when doing an Uncached Access.
assign BusTransComplete = (UnCachedRW) ? BusAck : WordCountFlag & BusAck;
// Use SEQ if not doing first word, NONSEQ if doing the first read/write, and IDLE if finishing up.
assign HTRANS = (|WordCount) & ~UnCachedRW ? AHB_SEQ : (BusRead | BusWrite) & (~BusTransComplete) ? AHB_NONSEQ : AHB_IDLE;
// Reset if we aren't initiating a transaction or if we are finishing a transaction.
assign CntReset = BusCurrState == STATE_BUS_READY & ~(CacheFetchLine | CacheWriteLine) | BusTransComplete;
assign BusStall = (BusCurrState == STATE_BUS_READY & ~IgnoreRequest & ((UnCachedAccess & (|RW)) | CacheFetchLine | CacheWriteLine)) |
(BusCurrState == STATE_BUS_UNCACHED_WRITE) |
(BusCurrState == STATE_BUS_UNCACHED_READ) |
(BusCurrState == STATE_BUS_FETCH) |
(BusCurrState == STATE_BUS_WRITE);
assign UnCachedBusWrite = (BusCurrState == STATE_BUS_READY & UnCachedAccess & RW[0] & ~IgnoreRequest) |
(BusCurrState == STATE_BUS_UNCACHED_WRITE);
assign BusWrite = UnCachedBusWrite | (BusCurrState == STATE_BUS_WRITE & ~WordCountFlag);
assign SelBusWord = (BusCurrState == STATE_BUS_READY & UnCachedAccess & RW[0]) |
(BusCurrState == STATE_BUS_UNCACHED_WRITE) |
(BusCurrState == STATE_BUS_WRITE);
assign UnCachedBusRead = (BusCurrState == STATE_BUS_READY & UnCachedAccess & RW[1] & ~IgnoreRequest) |
(BusCurrState == STATE_BUS_UNCACHED_READ);
assign BusRead = UnCachedBusRead | (BusCurrState == STATE_BUS_FETCH & ~(WordCountFlag)) | (BusCurrState == STATE_BUS_READY & CacheFetchLine);
assign BufferCaptureEn = UnCachedBusRead | BusCurrState == STATE_BUS_FETCH;
// Makes bus only do uncached reads/writes when we actually do uncached reads/writes. Needed because Cacheable is 0 when flushing cache.
assign UnCachedRW = UnCachedBusWrite | UnCachedBusRead;
assign CacheBusAck = (BusCurrState == STATE_BUS_FETCH & WordCountFlag & BusAck) |
(BusCurrState == STATE_BUS_WRITE & WordCountFlag & BusAck);
assign BusCommitted = BusCurrState != STATE_BUS_READY;
assign SelUncachedAdr = (BusCurrState == STATE_BUS_READY & (|RW & UnCachedAccess)) |
(BusCurrState == STATE_BUS_UNCACHED_READ |
BusCurrState == STATE_BUS_UNCACHED_READ_DONE |
BusCurrState == STATE_BUS_UNCACHED_WRITE |
BusCurrState == STATE_BUS_UNCACHED_WRITE_DONE) |
~CACHE_ENABLED; // if no Cache always select uncachedadr.
endmodule

2
pipelined/src/lsu/busdp.sv
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@ -88,7 +88,7 @@ module busdp #(parameter WORDSPERLINE, LINELEN, LOGWPL, CACHE_ENABLED)
mux2 #(3) sizemux(.d0(`XLEN == 32 ? 3'b010 : 3'b011), .d1(Funct3), .s(SelUncachedAdr), .y(HSIZE));
busfsm #(WordCountThreshold, LOGWPL, CACHE_ENABLED) busfsm(
buscachefsm #(WordCountThreshold, LOGWPL, CACHE_ENABLED) buscachefsm(
.clk, .reset, .IgnoreRequest, .RW, .CacheFetchLine, .CacheWriteLine,
.BusAck, .BusInit, .CPUBusy, .Cacheable, .BusStall, .BusWrite, .SelBusWord, .BusRead, .BufferCaptureEn,
.HBURST, .HTRANS, .BusTransComplete, .CacheBusAck, .BusCommitted, .SelUncachedAdr, .WordCount, .WordCountDelayed);

2
pipelined/src/lsu/busfsm.sv
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@ -4,7 +4,7 @@
// Written: Ross Thompson ross1728@gmail.com December 29, 2021
// Modified:
//
// Purpose: Load/Store Unit's interface to BUS
// Purpose: Load/Store Unit's interface to BUS for cacheless system
//
// A component of the Wally configurable RISC-V project.
//