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Merge pull request #25 from ross144/main

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Moved ebufsmarb into its own module.
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David Harris 2023-01-24 04:45:51 -08:00 committed by GitHub
commit 1ca3e43637
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3 changed files with 127 additions and 72 deletions
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4
gitflow.txt
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@ -40,6 +40,6 @@ Create pull request
6. Wait for pull request to be approved, rejected, or needs changes.
7. Finish by fetching the upstream and pushing back to your fork.
1. git fetch upstream
2. git merge upstream/main
3. git push
2. git merge upstream/main # sync your clone with the upstream
3. git push # sync your fork with the upstream and clone

74
pipelined/src/ebu/ebu.sv
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@ -66,8 +66,6 @@ module ebu (
output logic HMASTLOCK // AHB master lock. Wally does not use
);
typedef enum logic [1:0] {IDLE, ARBITRATE} statetype;
statetype CurrState, NextState;
logic LSUDisable;
logic LSUSelect;
@ -75,7 +73,6 @@ module ebu (
logic IFURestore;
logic IFUDisable;
logic IFUSelect;
logic both; // Both the LSU and IFU request at the same time
logic [`PA_BITS-1:0] IFUHADDROut;
logic [1:0] IFUHTRANSOut;
@ -92,12 +89,6 @@ module ebu (
logic IFUReq;
logic LSUReq;
logic BeatCntEn;
logic [4-1:0] NextBeatCount, BeatCount; // Position within a burst transfer
logic FinalBeat, FinalBeatD; // Indicates the last beat of a burst
logic CntReset;
logic [3:0] Threshold; // Number of beats derived from HBURST
logic IFUReqD; // 1 cycle delayed IFU request. Part of arbitration
assign HCLK = clk;
@ -137,66 +128,9 @@ module ebu (
assign HWSTRB = LSUHWSTRB;
// HRDATA is sent to all controllers at the core level.
////////////////////////////////////////////////////////////////////////////////////////////////////
// Aribtration scheme
// FSM decides if arbitration needed. Arbitration is held until the last beat of
// a burst is completed.
////////////////////////////////////////////////////////////////////////////////////////////////////
assign both = LSUReq & IFUReq;
flopenl #(.TYPE(statetype)) busreg(HCLK, ~HRESETn, 1'b1, NextState, IDLE, CurrState);
always_comb
case (CurrState)
IDLE: if (both) NextState = ARBITRATE;
else NextState = IDLE;
ARBITRATE: if (HREADY & FinalBeatD & ~(LSUReq & IFUReq)) NextState = IDLE;
else NextState = ARBITRATE;
default: NextState = IDLE;
endcase
// basic arb always selects LSU when both
// replace this block for more sophisticated arbitration as needed.
// Controller 0 (IFU)
assign IFUSave = CurrState == IDLE & both;
assign IFURestore = CurrState == ARBITRATE;
assign IFUDisable = CurrState == ARBITRATE;
assign IFUSelect = (NextState == ARBITRATE) ? 1'b0 : IFUReq;
// Controller 1 (LSU)
// When both the IFU and LSU request at the same time, the FSM will go into the arbitrate state.
// Once the LSU request is done the fsm returns to IDLE. To prevent the LSU from regaining
// priority and re issuing the same memroy operation, the delayed IFUReqD squashes the LSU request.
// This is necessary because the pipeline is stalled for the entire duration of both transactions,
// and the LSU memory request will stil be active.
flopr #(1) ifureqreg(clk, ~HRESETn, IFUReq, IFUReqD);
assign LSUDisable = CurrState == ARBITRATE ? 1'b0 : (IFUReqD & ~(HREADY & FinalBeatD));
assign LSUSelect = NextState == ARBITRATE ? 1'b1: LSUReq;
////////////////////////////////////////////////////////////////////////////////////////////////////
// Burst mode logic
////////////////////////////////////////////////////////////////////////////////////////////////////
flopenr #(4) BeatCountReg(HCLK, ~HRESETn | CntReset | FinalBeat, BeatCntEn, NextBeatCount, BeatCount);
assign NextBeatCount = BeatCount + 1'b1;
assign CntReset = NextState == IDLE;
assign FinalBeat = (BeatCount == Threshold); // Detect when we are waiting on the final access.
assign BeatCntEn = (NextState == ARBITRATE & HREADY);
// Used to store data from data phase of AHB.
flopenr #(1) FinalBeatReg(HCLK, ~HRESETn | CntReset, BeatCntEn, FinalBeat, FinalBeatD);
// unlike the bus fsm in lsu/ifu, we need to derive the number of beats from HBURST.
always_comb begin
case(HBURST)
0: Threshold = 4'b0000;
3: Threshold = 4'b0011; // INCR4
5: Threshold = 4'b0111; // INCR8
7: Threshold = 4'b1111; // INCR16
default: Threshold = 4'b0000; // INCR without end.
endcase
end
ebufsmarb ebufsmarb(.HCLK, .HRESETn, .HBURST, .HREADY, .LSUReq, .IFUReq, .IFUSave,
.IFURestore, .IFUDisable, .IFUSelect, .LSUDisable, .LSUSelect);
endmodule

121
pipelined/src/ebu/ebuarbfsm.sv Normal file
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@ -0,0 +1,121 @@
///////////////////////////////////////////
// ebufsmarb
//
// Written: Ross Thompson ross1728@gmail.com
// Created: 23 January 2023
// Modified: 23 January 2023
//
// Purpose: Arbitrates requests from instruction and data streams
// LSU has priority.
//
// Documentation: RISC-V System on Chip Design Chapter 6 (Figures 6.25 and 6.26)
//
// A component of the CORE-V-WALLY configurable RISC-V project.
//
// Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
//
// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
//
// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file
// except in compliance with the License, or, at your option, the Apache License version 2.0. You
// may obtain a copy of the License at
//
// https://solderpad.org/licenses/SHL-2.1/
//
// Unless required by applicable law or agreed to in writing, any work distributed under the
// License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
// either express or implied. See the License for the specific language governing permissions
// and limitations under the License.
////////////////////////////////////////////////////////////////////////////////////////////////
`include "wally-config.vh"
module ebufsmarb (
input logic HCLK,
input logic HRESETn,
input logic [2:0] HBURST,
// AHB burst length
input logic HREADY,
input logic LSUReq,
input logic IFUReq,
output logic IFUSave,
output logic IFURestore,
output logic IFUDisable,
output logic IFUSelect,
output logic LSUDisable,
output logic LSUSelect);
typedef enum logic [1:0] {IDLE, ARBITRATE} statetype;
statetype CurrState, NextState;
logic both; // Both the LSU and IFU request at the same time
logic IFUReqD; // 1 cycle delayed IFU request. Part of arbitration
logic FinalBeat, FinalBeatD; // Indicates the last beat of a burst
logic BeatCntEn;
logic [4-1:0] NextBeatCount, BeatCount; // Position within a burst transfer
logic CntReset;
logic [3:0] Threshold; // Number of beats derived from HBURST
////////////////////////////////////////////////////////////////////////////////////////////////////
// Aribtration scheme
// FSM decides if arbitration needed. Arbitration is held until the last beat of
// a burst is completed.
////////////////////////////////////////////////////////////////////////////////////////////////////
assign both = LSUReq & IFUReq;
flopenl #(.TYPE(statetype)) busreg(HCLK, ~HRESETn, 1'b1, NextState, IDLE, CurrState);
always_comb
case (CurrState)
IDLE: if (both) NextState = ARBITRATE;
else NextState = IDLE;
ARBITRATE: if (HREADY & FinalBeatD & ~(LSUReq & IFUReq)) NextState = IDLE;
else NextState = ARBITRATE;
default: NextState = IDLE;
endcase
// basic arb always selects LSU when both
// replace this block for more sophisticated arbitration as needed.
// Controller 0 (IFU)
assign IFUSave = CurrState == IDLE & both;
assign IFURestore = CurrState == ARBITRATE;
assign IFUDisable = CurrState == ARBITRATE;
assign IFUSelect = (NextState == ARBITRATE) ? 1'b0 : IFUReq;
// Controller 1 (LSU)
// When both the IFU and LSU request at the same time, the FSM will go into the arbitrate state.
// Once the LSU request is done the fsm returns to IDLE. To prevent the LSU from regaining
// priority and re issuing the same memroy operation, the delayed IFUReqD squashes the LSU request.
// This is necessary because the pipeline is stalled for the entire duration of both transactions,
// and the LSU memory request will stil be active.
flopr #(1) ifureqreg(HCLK, ~HRESETn, IFUReq, IFUReqD);
assign LSUDisable = CurrState == ARBITRATE ? 1'b0 : (IFUReqD & ~(HREADY & FinalBeatD));
assign LSUSelect = NextState == ARBITRATE ? 1'b1: LSUReq;
////////////////////////////////////////////////////////////////////////////////////////////////////
// Burst mode logic
////////////////////////////////////////////////////////////////////////////////////////////////////
flopenr #(4) BeatCountReg(HCLK, ~HRESETn | CntReset | FinalBeat, BeatCntEn, NextBeatCount, BeatCount);
assign NextBeatCount = BeatCount + 1'b1;
assign CntReset = NextState == IDLE;
assign FinalBeat = (BeatCount == Threshold); // Detect when we are waiting on the final access.
assign BeatCntEn = (NextState == ARBITRATE & HREADY);
// Used to store data from data phase of AHB.
flopenr #(1) FinalBeatReg(HCLK, ~HRESETn | CntReset, BeatCntEn, FinalBeat, FinalBeatD);
// unlike the bus fsm in lsu/ifu, we need to derive the number of beats from HBURST.
always_comb begin
case(HBURST)
0: Threshold = 4'b0000;
3: Threshold = 4'b0011; // INCR4
5: Threshold = 4'b0111; // INCR8
7: Threshold = 4'b1111; // INCR16
default: Threshold = 4'b0000; // INCR without end.
endcase
end
endmodule