///////////////////////////////////////////
// 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,

  input  logic [31:0] HADDR,
  input  logic [2:0]  HSIZE,
  input  logic [2:0]  HBURST,

  input  logic        AtomicAccessM, ExecuteAccessF, WriteAccessM, ReadAccessM,

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

  output logic [5:0]  HSELRegions,

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

  // Signals are high if the memory access is within the given region
  logic HSELBootTim, HSELTim, HSELCLINT, HSELGPIO, HSELUART, HSELPLIC;

  logic PreHSELUART;

  logic ExecutableRegion, ReadableRegion, WritableRegion;
  logic Empty;

  // Determine which region of physical memory (if any) is being accessed
  adrdec boottimdec(HADDR, `BOOTTIMBASE, `BOOTTIMRANGE, HSELBootTim);
  adrdec timdec(HADDR, `TIMBASE, `TIMRANGE, HSELTim);
  adrdec clintdec(HADDR, `CLINTBASE, `CLINTRANGE, HSELCLINT);
  adrdec gpiodec(HADDR, `GPIOBASE, `GPIORANGE, HSELGPIO);
  adrdec uartdec(HADDR, `UARTBASE, `UARTRANGE, PreHSELUART);
  adrdec plicdec(HADDR, `PLICBASE, `PLICRANGE, HSELPLIC);

  // *** Should this fault?
  assign HSELUART = PreHSELUART && (HSIZE == 3'b000); // only byte writes to UART are supported

  // Swizzle region bits
  assign HSELRegions = {HSELBootTim, HSELTim, HSELCLINT, HSELGPIO, HSELUART, HSELPLIC};

  // Only RAM memory regions are cacheable
  assign Cacheable = HSELBootTim | HSELTim;

  // *** Temporarily assume only RAM regions are idempotent -- likely wrong
  assign Idempotent = HSELBootTim | HSELTim;

  // *** Temporarily assume only RAM regions allow full atomic operations -- likely wrong
  assign AtomicAllowed = HSELBootTim | HSELTim;

  assign ExecutableRegion = HSELBootTim | HSELTim;
  assign ReadableRegion = HSELBootTim | HSELTim | HSELCLINT | HSELGPIO | HSELUART | HSELPLIC;
  assign WritableRegion = HSELBootTim | HSELTim | HSELCLINT | HSELGPIO | HSELUART | HSELPLIC;

  assign Empty = ~|HSELRegions;

  assign PMAInstrAccessFaultF = ExecuteAccessF && (Empty || ~ExecutableRegion);
  assign PMALoadAccessFaultM = ReadAccessM && (Empty || ~ReadableRegion);
  assign PMAStoreAccessFaultM = WriteAccessM && (Empty || ~WritableRegion);

  //assign PMASquashBusAccess = PMAInstrAccessFaultF || PMALoadAccessFaultM || PMAStoreAccessFaultM;
  assign PMASquashBusAccess = 0;

endmodule