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cvw/src/privileged/csrm.sv
David Harris e713ba8d3e MENVCFG only exists if U_SUPPORTED
2023-07-09 18:25:07 -07:00

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///////////////////////////////////////////
// csrm.sv
//
// Written: David_Harris@hmc.edu 9 January 2021
// Modified:
// dottolia@hmc.edu 7 April 2021
//
// Purpose: Machine-Mode Control and Status Registers
// See RISC-V Privileged Mode Specification 20190608
// Note: the CSRs do not support the following optional features
// - Disabling portions of the instruction set with bits of the MISA register
// - Changing from RV64 to RV32 by writing the SXL/UXL bits of the STATUS register
//
// Documentation: RISC-V System on Chip Design Chapter 5
//
// 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.
////////////////////////////////////////////////////////////////////////////////////////////////
module csrm import cvw::*; #(parameter cvw_t P) (
input logic clk, reset,
input logic UngatedCSRMWriteM, CSRMWriteM, MTrapM,
input logic [11:0] CSRAdrM,
input logic [P.XLEN-1:0] NextEPCM, NextMtvalM, MSTATUS_REGW, MSTATUSH_REGW,
input logic [4:0] NextCauseM,
input logic [P.XLEN-1:0] CSRWriteValM,
input logic [11:0] MIP_REGW, MIE_REGW,
output logic [P.XLEN-1:0] CSRMReadValM, MTVEC_REGW,
output logic [P.XLEN-1:0] MEPC_REGW,
output logic [31:0] MCOUNTEREN_REGW, MCOUNTINHIBIT_REGW,
output logic [15:0] MEDELEG_REGW,
output logic [11:0] MIDELEG_REGW,
output var logic [7:0] PMPCFG_ARRAY_REGW[P.PMP_ENTRIES-1:0],
output var logic [P.PA_BITS-3:0] PMPADDR_ARRAY_REGW [P.PMP_ENTRIES-1:0],
output logic WriteMSTATUSM, WriteMSTATUSHM,
output logic IllegalCSRMAccessM, IllegalCSRMWriteReadonlyM,
output logic [63:0] MENVCFG_REGW
);
logic [P.XLEN-1:0] MISA_REGW, MHARTID_REGW;
logic [P.XLEN-1:0] MSCRATCH_REGW, MTVAL_REGW, MCAUSE_REGW;
logic [P.XLEN-1:0] MENVCFGH_REGW;
logic WriteMTVECM, WriteMEDELEGM, WriteMIDELEGM;
logic WriteMSCRATCHM, WriteMEPCM, WriteMCAUSEM, WriteMTVALM;
logic WriteMCOUNTERENM, WriteMCOUNTINHIBITM;
// Machine CSRs
localparam MVENDORID = 12'hF11;
localparam MARCHID = 12'hF12;
localparam MIMPID = 12'hF13;
localparam MHARTID = 12'hF14;
localparam MCONFIGPTR = 12'hF15;
localparam MSTATUS = 12'h300;
localparam MISA_ADR = 12'h301;
localparam MEDELEG = 12'h302;
localparam MIDELEG = 12'h303;
localparam MIE = 12'h304;
localparam MTVEC = 12'h305;
localparam MCOUNTEREN = 12'h306;
localparam MENVCFG = 12'h30A;
localparam MSTATUSH = 12'h310;
localparam MENVCFGH = 12'h31A;
localparam MCOUNTINHIBIT = 12'h320;
localparam MSCRATCH = 12'h340;
localparam MEPC = 12'h341;
localparam MCAUSE = 12'h342;
localparam MTVAL = 12'h343;
localparam MIP = 12'h344;
localparam PMPCFG0 = 12'h3A0;
// .. up to 15 more at consecutive addresses
localparam PMPADDR0 = 12'h3B0;
// ... up to 63 more at consecutive addresses
localparam TSELECT = 12'h7A0;
localparam TDATA1 = 12'h7A1;
localparam TDATA2 = 12'h7A2;
localparam TDATA3 = 12'h7A3;
localparam DCSR = 12'h7B0;
localparam DPC = 12'h7B1;
localparam DSCRATCH0 = 12'h7B2;
localparam DSCRATCH1 = 12'h7B3;
// Constants
localparam ZERO = {(P.XLEN){1'b0}};
localparam MEDELEG_MASK = 16'hB3FF;
localparam MIDELEG_MASK = 12'h222; // we choose to not make machine interrupts delegable
// There are PMP_ENTRIES = 0, 16, or 64 PMPADDR registers, each of which has its own flop
genvar i;
if (P.PMP_ENTRIES > 0) begin:pmp
logic [P.PMP_ENTRIES-1:0] WritePMPCFGM;
logic [P.PMP_ENTRIES-1:0] WritePMPADDRM ;
logic [P.PMP_ENTRIES-1:0] ADDRLocked, CFGLocked;
for(i=0; i<P.PMP_ENTRIES; i++) begin
// when the lock bit is set, don't allow writes to the PMPCFG or PMPADDR
// also, when the lock bit of the next entry is set and the next entry is TOR, don't allow writes to this entry PMPADDR
assign CFGLocked[i] = PMPCFG_ARRAY_REGW[i][7];
if (i == P.PMP_ENTRIES-1)
assign ADDRLocked[i] = PMPCFG_ARRAY_REGW[i][7];
else
assign ADDRLocked[i] = PMPCFG_ARRAY_REGW[i][7] | (PMPCFG_ARRAY_REGW[i+1][7] & PMPCFG_ARRAY_REGW[i+1][4:3] == 2'b01);
assign WritePMPADDRM[i] = (CSRMWriteM & (CSRAdrM == (PMPADDR0+i))) & ~ADDRLocked[i];
flopenr #(P.PA_BITS-2) PMPADDRreg(clk, reset, WritePMPADDRM[i], CSRWriteValM[P.PA_BITS-3:0], PMPADDR_ARRAY_REGW[i]);
if (P.XLEN==64) begin
assign WritePMPCFGM[i] = (CSRMWriteM & (CSRAdrM == (PMPCFG0+2*(i/8)))) & ~CFGLocked[i];
flopenr #(8) PMPCFGreg(clk, reset, WritePMPCFGM[i], CSRWriteValM[(i%8)*8+7:(i%8)*8], PMPCFG_ARRAY_REGW[i]);
end else begin
assign WritePMPCFGM[i] = (CSRMWriteM & (CSRAdrM == (PMPCFG0+i/4))) & ~CFGLocked[i];
flopenr #(8) PMPCFGreg(clk, reset, WritePMPCFGM[i], CSRWriteValM[(i%4)*8+7:(i%4)*8], PMPCFG_ARRAY_REGW[i]);
end
end
end
localparam MISA_26 = (P.MISA) & 32'h03ffffff;
// MISA is hardwired. Spec says it could be written to disable features, but this is not supported by Wally
assign MISA_REGW = {(P.XLEN == 32 ? 2'b01 : 2'b10), {(P.XLEN-28){1'b0}}, MISA_26[25:0]};
// MHARTID is hardwired. It only exists as a signal so that the testbench can easily see it.
assign MHARTID_REGW = 0;
// Write machine Mode CSRs
assign WriteMSTATUSM = CSRMWriteM & (CSRAdrM == MSTATUS);
assign WriteMSTATUSHM = CSRMWriteM & (CSRAdrM == MSTATUSH) & (P.XLEN==32);
assign WriteMTVECM = CSRMWriteM & (CSRAdrM == MTVEC);
assign WriteMEDELEGM = CSRMWriteM & (CSRAdrM == MEDELEG);
assign WriteMIDELEGM = CSRMWriteM & (CSRAdrM == MIDELEG);
assign WriteMSCRATCHM = CSRMWriteM & (CSRAdrM == MSCRATCH);
assign WriteMEPCM = MTrapM | (CSRMWriteM & (CSRAdrM == MEPC));
assign WriteMCAUSEM = MTrapM | (CSRMWriteM & (CSRAdrM == MCAUSE));
assign WriteMTVALM = MTrapM | (CSRMWriteM & (CSRAdrM == MTVAL));
assign WriteMCOUNTERENM = CSRMWriteM & (CSRAdrM == MCOUNTEREN);
assign WriteMCOUNTINHIBITM = CSRMWriteM & (CSRAdrM == MCOUNTINHIBIT);
assign IllegalCSRMWriteReadonlyM = UngatedCSRMWriteM & (CSRAdrM == MVENDORID | CSRAdrM == MARCHID | CSRAdrM == MIMPID | CSRAdrM == MHARTID);
// CSRs
flopenr #(P.XLEN) MTVECreg(clk, reset, WriteMTVECM, {CSRWriteValM[P.XLEN-1:2], 1'b0, CSRWriteValM[0]}, MTVEC_REGW);
if (P.S_SUPPORTED) begin:deleg // DELEG registers should exist
flopenr #(16) MEDELEGreg(clk, reset, WriteMEDELEGM, CSRWriteValM[15:0] & MEDELEG_MASK, MEDELEG_REGW);
flopenr #(12) MIDELEGreg(clk, reset, WriteMIDELEGM, CSRWriteValM[11:0] & MIDELEG_MASK, MIDELEG_REGW);
end else assign {MEDELEG_REGW, MIDELEG_REGW} = 0;
flopenr #(P.XLEN) MSCRATCHreg(clk, reset, WriteMSCRATCHM, CSRWriteValM, MSCRATCH_REGW);
flopenr #(P.XLEN) MEPCreg(clk, reset, WriteMEPCM, NextEPCM, MEPC_REGW);
flopenr #(P.XLEN) MCAUSEreg(clk, reset, WriteMCAUSEM, {NextCauseM[4], {(P.XLEN-5){1'b0}}, NextCauseM[3:0]}, MCAUSE_REGW);
if(P.QEMU) assign MTVAL_REGW = '0; // MTVAL tied to 0 in QEMU configuration
else flopenr #(P.XLEN) MTVALreg(clk, reset, WriteMTVALM, NextMtvalM, MTVAL_REGW);
flopenr #(32) MCOUNTINHIBITreg(clk, reset, WriteMCOUNTINHIBITM, CSRWriteValM[31:0], MCOUNTINHIBIT_REGW);
if (P.U_SUPPORTED) begin: mcounteren // MCOUNTEREN only exists when user mode is supported
flopenr #(32) MCOUNTERENreg(clk, reset, WriteMCOUNTERENM, CSRWriteValM[31:0], MCOUNTEREN_REGW);
end else assign MCOUNTEREN_REGW = '0;
// MENVCFG register
if (P.U_SUPPORTED) begin // menvcfg only exists if there is a lower privilege to control
logic WriteMENVCFGM;
logic [63:0] MENVCFG_PreWriteValM, MENVCFG_WriteValM;
assign WriteMENVCFGM = CSRMWriteM & (CSRAdrM == MENVCFG);
// MENVCFG is always 64 bits even for RV32
assign MENVCFG_WriteValM = {
MENVCFG_PreWriteValM[63] & P.SSTC_SUPPORTED,
MENVCFG_PreWriteValM[62] & P.SVPBMT_SUPPORTED,
54'b0,
MENVCFG_PreWriteValM[7] & P.ZICBOZ_SUPPORTED,
MENVCFG_PreWriteValM[6:4] & {3{P.ZICBOM_SUPPORTED}},
3'b0,
MENVCFG_PreWriteValM[0] & P.S_SUPPORTED & P.VIRTMEM_SUPPORTED
};
if (P.XLEN == 64) begin
assign MENVCFG_PreWriteValM = CSRWriteValM;
flopenr #(P.XLEN) MENVCFGreg(clk, reset, WriteMENVCFGM, MENVCFG_WriteValM, MENVCFG_REGW);
assign MENVCFGH_REGW = 0;
end else begin // RV32 has high and low halves
logic WriteMENVCFGHM;
assign MENVCFG_PreWriteValM = {CSRWriteValM, CSRWriteValM};
assign WriteMENVCFGHM = CSRMWriteM & (CSRAdrM == MENVCFGH) & (P.XLEN==32);
flopenr #(P.XLEN) MENVCFGreg(clk, reset, WriteMENVCFGM, MENVCFG_WriteValM[31:0], MENVCFG_REGW[31:0]);
flopenr #(P.XLEN) MENVCFGHreg(clk, reset, WriteMENVCFGHM, MENVCFG_WriteValM[63:32], MENVCFG_REGW[63:32]);
assign MENVCFGH_REGW = MENVCFG_REGW[63:32];
end
end
// Read machine mode CSRs
// verilator lint_off WIDTH
logic [5:0] entry;
always_comb begin
entry = '0;
CSRMReadValM = 0;
IllegalCSRMAccessM = !(P.S_SUPPORTED) & (CSRAdrM == MEDELEG | CSRAdrM == MIDELEG); // trap on DELEG register access when no S or N-mode
if (CSRAdrM >= PMPADDR0 & CSRAdrM < PMPADDR0 + P.PMP_ENTRIES) // reading a PMP entry
CSRMReadValM = {{(P.XLEN-(P.PA_BITS-2)){1'b0}}, PMPADDR_ARRAY_REGW[CSRAdrM - PMPADDR0]};
else if (CSRAdrM >= PMPCFG0 & CSRAdrM < PMPCFG0 + P.PMP_ENTRIES/4 & (P.XLEN==32 | CSRAdrM[0] == 0)) begin
// only odd-numbered PMPCFG entries exist in RV64
if (P.XLEN==64) begin
entry = ({CSRAdrM[11:1], 1'b0} - PMPCFG0)*4; // disregard odd entries in RV64
CSRMReadValM = {PMPCFG_ARRAY_REGW[entry+7],PMPCFG_ARRAY_REGW[entry+6],PMPCFG_ARRAY_REGW[entry+5],PMPCFG_ARRAY_REGW[entry+4],
PMPCFG_ARRAY_REGW[entry+3],PMPCFG_ARRAY_REGW[entry+2],PMPCFG_ARRAY_REGW[entry+1],PMPCFG_ARRAY_REGW[entry]};
end else begin
entry = (CSRAdrM - PMPCFG0)*4;
CSRMReadValM = {PMPCFG_ARRAY_REGW[entry+3],PMPCFG_ARRAY_REGW[entry+2],PMPCFG_ARRAY_REGW[entry+1],PMPCFG_ARRAY_REGW[entry]};
end
end
else case (CSRAdrM)
MISA_ADR: CSRMReadValM = MISA_REGW;
MVENDORID: CSRMReadValM = 0;
MARCHID: CSRMReadValM = 0;
MIMPID: CSRMReadValM = {{P.XLEN-12{1'b0}}, 12'h100}; // pipelined implementation
MHARTID: CSRMReadValM = MHARTID_REGW; // hardwired to 0
MCONFIGPTR: CSRMReadValM = 0; // hardwired to 0
MSTATUS: CSRMReadValM = MSTATUS_REGW;
MSTATUSH: if (P.XLEN==32) CSRMReadValM = MSTATUSH_REGW;
else IllegalCSRMAccessM = 1;
MTVEC: CSRMReadValM = MTVEC_REGW;
MEDELEG: CSRMReadValM = {{(P.XLEN-16){1'b0}}, MEDELEG_REGW};
MIDELEG: CSRMReadValM = {{(P.XLEN-12){1'b0}}, MIDELEG_REGW};
MIP: CSRMReadValM = {{(P.XLEN-12){1'b0}}, MIP_REGW};
MIE: CSRMReadValM = {{(P.XLEN-12){1'b0}}, MIE_REGW};
MSCRATCH: CSRMReadValM = MSCRATCH_REGW;
MEPC: CSRMReadValM = MEPC_REGW;
MCAUSE: CSRMReadValM = MCAUSE_REGW;
MTVAL: CSRMReadValM = MTVAL_REGW;
MCOUNTEREN: CSRMReadValM = {{(P.XLEN-32){1'b0}}, MCOUNTEREN_REGW};
MENVCFG: if (P.U_SUPPORTED) CSRMReadValM = MENVCFG_REGW[P.XLEN-1:0];
else IllegalCSRMAccessM = 1;
MENVCFGH: if (P.U_SUPPORTED & P.XLEN==32) CSRMReadValM = MENVCFGH_REGW;
else IllegalCSRMAccessM = 1;
MCOUNTINHIBIT: CSRMReadValM = {{(P.XLEN-32){1'b0}}, MCOUNTINHIBIT_REGW};
default: IllegalCSRMAccessM = 1;
endcase
end
// verilator lint_on WIDTH
endmodule
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