2025-yatcpu/lab2/朱梓涵24325356/scala/riscv/core/CLINT.scala

// Copyright 2021 Howard Lau
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// 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.

package riscv.core

import chisel3._
import chisel3.util._
import riscv.Parameters

object InterruptCode {
  val None = 0x0.U(8.W)
  val Timer0 = 0x1.U(8.W)
  val Ret = 0xFF.U(8.W)
}

object InterruptEntry {
  val Timer0 = 0x4.U(8.W)
}


class CSRDirectAccessBundle extends Bundle {
  val mstatus = Input(UInt(Parameters.DataWidth))
  val mepc = Input(UInt(Parameters.DataWidth))
  val mcause = Input(UInt(Parameters.DataWidth))
  val mtvec = Input(UInt(Parameters.DataWidth))

  val mstatus_write_data= Output(UInt(Parameters.DataWidth))
  val mepc_write_data= Output(UInt(Parameters.DataWidth))
  val mcause_write_data= Output(UInt(Parameters.DataWidth))

  val direct_write_enable = Output(Bool())
}

// Core Local Interrupt Controller
class CLINT extends Module {
  val io = IO(new Bundle {
    // Interrupt signals from peripherals
    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))

    val instruction = Input(UInt(Parameters.InstructionWidth))
    val instruction_address = Input(UInt(Parameters.AddrWidth))

    val jump_flag = Input(Bool())
    val jump_address = Input(UInt(Parameters.AddrWidth))

    val interrupt_handler_address = Output(UInt(Parameters.AddrWidth))
    val interrupt_assert = Output(Bool())

    val csr_bundle = new CSRDirectAccessBundle
  })
  val interrupt_enable = io.csr_bundle.mstatus(3)
  val instruction_address = Mux(
    io.jump_flag,
    io.jump_address,
    io.instruction_address + 4.U,
  )
  //lab2(CLINTCSR)
  val mstatus = io.csr_bundle.mstatus
  val mie = mstatus(3)
  val mpie = mstatus(7)
  // 优先级顺序至关重要：
  // 1. 外部硬件中断具有最高优先级，可以“覆盖”当前指令的行为。
  // 2. 如果没有外部中断，再判断当前指令是否是陷阱指令 (mret, ecall, ebreak)。
  when(io.interrupt_flag =/= InterruptCode.None && interrupt_enable) {
    // 处理硬件中断 (最高优先级)
    io.interrupt_assert := true.B
    io.csr_bundle.direct_write_enable := true.B
    io.interrupt_handler_address := io.csr_bundle.mtvec // 跳转到中断向量
    io.csr_bundle.mepc_write_data := instruction_address // 保存下一条指令地址
    io.csr_bundle.mcause_write_data := Mux(
      io.interrupt_flag === InterruptCode.Timer0,
      "h80000007".U(Parameters.DataWidth),
      "h8000000B".U(Parameters.DataWidth)
    )
    // 更新 mstatus: MIE <- 0, MPIE <- MIE
    val new_mpie = mie << 7
    io.csr_bundle.mstatus_write_data := (mstatus & (~(1.U << 3)).asUInt) | new_mpie | (3.U << 11)
  }.elsewhen(io.instruction === InstructionsRet.mret) {
    // 处理 mret
    io.interrupt_assert := true.B
    io.csr_bundle.direct_write_enable := true.B
    io.interrupt_handler_address := io.csr_bundle.mepc // 跳转回 mepc
    // mstatus 更新: MIE <- MPIE, MPIE <- 1
    val new_mie = mpie << 3
    io.csr_bundle.mstatus_write_data := (mstatus & (~(1.U << 7)).asUInt) | new_mie | (1.U << 7) | (3.U << 11)

    // mret 不更新 mepc 和 mcause
    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
  }.elsewhen(io.instruction === InstructionsEnv.ecall) {
    // 处理 ecall
    io.interrupt_assert := true.B
    io.csr_bundle.direct_write_enable := true.B
    io.interrupt_handler_address := io.csr_bundle.mtvec
    io.csr_bundle.mepc_write_data := instruction_address
    io.csr_bundle.mcause_write_data := 11.U
    val new_mpie = mie << 7
    io.csr_bundle.mstatus_write_data := (mstatus & (~(1.U << 3)).asUInt) | new_mpie | (3.U << 11)
  }.elsewhen(io.instruction === InstructionsEnv.ebreak) {
    // 处理 ebreak
    io.interrupt_assert := true.B
    io.csr_bundle.direct_write_enable := true.B
    io.interrupt_handler_address := io.csr_bundle.mtvec
    io.csr_bundle.mepc_write_data := instruction_address
    io.csr_bundle.mcause_write_data := 3.U
    val new_mpie = mie << 7
    io.csr_bundle.mstatus_write_data := (mstatus & (~(1.U << 3)).asUInt) | new_mpie | (3.U << 11)
  }.otherwise {
    // 默认情况，所有信号都设为默认值
    io.interrupt_assert := false.B
    io.csr_bundle.direct_write_enable := false.B
    io.interrupt_handler_address := 0.U

    io.csr_bundle.mstatus_write_data := mstatus
    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
  }
}