cvw/wally-pipelined/src/mmu/pmachecker.sv

///////////////////////////////////////////
// pmachecker.sv
//
// Written: tfleming@hmc.edu & jtorrey@hmc.edu 20 April 2021
// Modified: 
//
// Purpose: Examines all physical memory accesses and identifies attributes of
//          the memory region accessed.
//          Can report illegal accesses to the trap unit and cause a fault.
// 
// A component of the Wally configurable RISC-V project.
// 
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// 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 pmachecker (
//  input  logic        clk, reset, // *** unused in this module and all sub modules.

  input  logic [`PA_BITS-1:0] PhysicalAddress,
  input  logic [1:0]          Size,

  input  logic        AtomicAccessM, ExecuteAccessF, WriteAccessM, ReadAccessM, // *** atomicaccessM is unused but might want to stay in for future use.

  output logic        Cacheable, Idempotent, AtomicAllowed,
  output logic        PMASquashBusAccess,

  output logic        PMAInstrAccessFaultF,
  output logic        PMALoadAccessFaultM,
  output logic        PMAStoreAccessFaultM
);

  logic PMAAccessFault;
  logic AccessRW, AccessRWX, AccessRX;
  logic [6:0]  SelRegions;

  // Determine what type of access is being made
  assign AccessRW = ReadAccessM | WriteAccessM;
  assign AccessRWX = ReadAccessM | WriteAccessM | ExecuteAccessF;
  assign AccessRX = ReadAccessM | ExecuteAccessF;

  // Determine which region of physical memory (if any) is being accessed
  adrdecs adrdecs(PhysicalAddress, AccessRW, AccessRX, AccessRWX, Size, SelRegions);

  // Only RAM memory regions are cacheable
  assign Cacheable = SelRegions[5] | SelRegions[4];
  assign Idempotent = SelRegions[4];
  assign AtomicAllowed = SelRegions[4];

  // Detect access faults
  assign PMAAccessFault = SelRegions[6] & AccessRWX;  
  assign PMAInstrAccessFaultF = ExecuteAccessF && PMAAccessFault;
  assign PMALoadAccessFaultM  = ReadAccessM    && PMAAccessFault;
  assign PMAStoreAccessFaultM = WriteAccessM   && PMAAccessFault;
  assign PMASquashBusAccess = PMAAccessFault;
endmodule