///////////////////////////////////////////
// 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 BootTim, Tim, CLINT, GPIO, UART, PLIC;
  logic [5:0] Regions;

  // Actual HSEL signals sent to uncore
  logic HSELBootTim, HSELTim, HSELCLINT, HSELGPIO, HSELUART, HSELPLIC;
  logic ValidBootTim, ValidTim, ValidCLINT, ValidGPIO, ValidUART, ValidPLIC;

  // Attributes of memory region accessed
  logic Executable, Readable, Writable;

  logic Fault;

  attributes attributes(.Address(HADDR), .*);

  // Unswizzle region bits
  assign {BootTim, Tim, CLINT, GPIO, UART, PLIC} = Regions;

  assign ValidBootTim = '1;
  assign ValidTim = '1;
  assign ValidCLINT = ~ExecuteAccessF && (HSIZE == 3'b010);
  assign ValidGPIO  = ~ExecuteAccessF && (HSIZE == 3'b010);
  assign ValidUART  = ~ExecuteAccessF && (HSIZE == 3'b000);

  assign HSELBootTim = BootTim && ValidBootTim; 
  assign HSELTim     = Tim     && ValidTim;
  assign HSELCLINT   = CLINT   && ValidCLINT;
  assign HSELGPIO    = GPIO    && ValidGPIO;
  assign HSELUART    = UART    && ValidUART; // only byte writes to UART are supported
  assign HSELPLIC    = PLIC    && ValidPLIC;

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

  assign Fault = ~|HSELRegions;

  assign PMAInstrAccessFaultF = ExecuteAccessF && Fault;
  assign PMALoadAccessFaultM  = ReadAccessM    && Fault;
  assign PMAStoreAccessFaultM = WriteAccessM   && Fault;

  assign PMASquashBusAccess = PMAInstrAccessFaultF || PMALoadAccessFaultM || PMAStoreAccessFaultM;

endmodule

module attributes (
  input  logic        clk, reset,

  input  logic [31:0] Address,

  output logic [5:0]  Regions,

  output logic        Cacheable, Idempotent, AtomicAllowed,
  output logic        Executable, Readable, Writable
);

  // Signals are high if the memory access is within the given region
  logic BootTim, Tim, CLINT, GPIO, UART, PLIC;

  // Determine which region of physical memory (if any) is being accessed
  adrdec boottimdec(Address, `BOOTTIMBASE, `BOOTTIMRANGE, BootTim);
  adrdec timdec(Address, `TIMBASE, `TIMRANGE, Tim);
  adrdec clintdec(Address, `CLINTBASE, `CLINTRANGE, CLINT);
  adrdec gpiodec(Address, `GPIOBASE, `GPIORANGE, GPIO);
  adrdec uartdec(Address, `UARTBASE, `UARTRANGE, UART);
  adrdec plicdec(Address, `PLICBASE, `PLICRANGE, PLIC);

  // Swizzle region bits
  assign Regions = {BootTim, Tim, CLINT, GPIO, UART, PLIC};

  // Only RAM memory regions are cacheable
  assign Cacheable = BootTim | Tim;

  assign Idempotent = BootTim | Tim;

  assign AtomicAllowed = BootTim | Tim;

  assign Executable = BootTim | Tim;
  assign Readable = BootTim | Tim | CLINT | GPIO | UART | PLIC;
  assign Writable = BootTim | Tim | CLINT | GPIO | UART | PLIC;

endmodule