cvw/pipelined/src/privileged/csrn.sv

104 lines
4.5 KiB
Systemverilog

///////////////////////////////////////////
// csrn.sv
//
// Written: David_Harris@hmc.edu 9 January 2021
// Modified:
// dottolia@hmc.edu 3 May 2021 - fix bug with utvec getting wrong value
//
// Purpose: User-Mode Control and Status Registers for User Mode Exceptions
// See RISC-V Privileged Mode Specification 20190608 Table 2.2
//
// 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 csrn #(parameter
USTATUS =12'h000,
UIE = 12'h004,
UTVEC = 12'h005,
USCRATCH = 12'h040,
UEPC = 12'h041,
UCAUSE = 12'h042,
UTVAL = 12'h043,
UIP = 12'h044) (
input logic clk, reset,
input logic InstrValidNotFlushedM, StallW,
input logic CSRNWriteM, UTrapM,
input logic [11:0] CSRAdrM,
input logic [`XLEN-1:0] NextEPCM, NextCauseM, NextMtvalM, USTATUS_REGW,
input logic [`XLEN-1:0] CSRWriteValM,
output logic [`XLEN-1:0] CSRNReadValM, UEPC_REGW, UTVEC_REGW,
input logic [11:0] UIP_REGW, UIE_REGW,
output logic WriteUSTATUSM,
output logic IllegalCSRNAccessM
);
// User mode CSRs below only needed when user mode traps are supported
if (`N_SUPPORTED) begin:nmode // depricated; consider removing***
logic WriteUTVECM;
logic WriteUSCRATCHM, WriteUEPCM;
logic WriteUCAUSEM, WriteUTVALM;
logic [`XLEN-1:0] UEDELEG_REGW, UIDELEG_REGW;
logic [`XLEN-1:0] USCRATCH_REGW, UCAUSE_REGW, UTVAL_REGW;
// Write enables
assign WriteUSTATUSM = CSRNWriteM & (CSRAdrM == USTATUS) & InstrValidNotFlushedM;
assign WriteUTVECM = CSRNWriteM & (CSRAdrM == UTVEC) & InstrValidNotFlushedM;
assign WriteUEPCM = UTrapM | (CSRNWriteM & (CSRAdrM == UEPC)) & InstrValidNotFlushedM;
assign WriteUCAUSEM = UTrapM | (CSRNWriteM & (CSRAdrM == UCAUSE)) & InstrValidNotFlushedM;
assign WriteUTVALM = UTrapM | (CSRNWriteM & (CSRAdrM == UTVAL)) & InstrValidNotFlushedM;
// CSRs
flopenl #(`XLEN) UTVECreg(clk, reset, WriteUTVECM, {CSRWriteValM[`XLEN-1:2], 1'b0, CSRWriteValM[0]}, `RESET_VECTOR, UTVEC_REGW);
flopenr #(`XLEN) USCRATCHreg(clk, reset, WriteUSCRATCHM, CSRWriteValM, USCRATCH_REGW);
flopenr #(`XLEN) UEPCreg(clk, reset, WriteUEPCM, NextEPCM, UEPC_REGW);
flopenr #(`XLEN) UCAUSEreg(clk, reset, WriteUCAUSEM, NextCauseM, UCAUSE_REGW);
flopenr #(`XLEN) UTVALreg(clk, reset, WriteUTVALM, NextMtvalM, UTVAL_REGW);
// CSR Reads
always_comb begin
IllegalCSRNAccessM = 0;
case (CSRAdrM)
USTATUS: CSRNReadValM = USTATUS_REGW;
UTVEC: CSRNReadValM = UTVEC_REGW;
UIP: CSRNReadValM = {{(`XLEN-12){1'b0}}, UIP_REGW};
UIE: CSRNReadValM = {{(`XLEN-12){1'b0}}, UIE_REGW};
USCRATCH: CSRNReadValM = USCRATCH_REGW;
UEPC: CSRNReadValM = UEPC_REGW;
UCAUSE: CSRNReadValM = UCAUSE_REGW;
UTVAL: CSRNReadValM = UTVAL_REGW;
default: begin
CSRNReadValM = 0;
IllegalCSRNAccessM = 1;
end
endcase
end
end else begin // if not supported
assign WriteUSTATUSM = 0;
assign CSRNReadValM = 0;
assign UEPC_REGW = 0;
assign UTVEC_REGW = 0;
assign IllegalCSRNAccessM = 1;
end
endmodule