实验报告检查

lab3/朱梓涵24325356/core/CSR.scala

@@ -0,0 +1,99 @@
+// 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
+import riscv.core.threestage.CSRDirectAccessBundle
+
+
+object CSRRegister {
+  // Refer to Spec. Vol.II Page 8-10
+  val MSTATUS = 0x300.U(Parameters.CSRRegisterAddrWidth)
+  val MIE = 0x304.U(Parameters.CSRRegisterAddrWidth)
+  val MTVEC = 0x305.U(Parameters.CSRRegisterAddrWidth)
+  val MSCRATCH = 0x340.U(Parameters.CSRRegisterAddrWidth)
+  val MEPC = 0x341.U(Parameters.CSRRegisterAddrWidth)
+  val MCAUSE = 0x342.U(Parameters.CSRRegisterAddrWidth)
+  val CycleL = 0xc00.U(Parameters.CSRRegisterAddrWidth)
+  val CycleH = 0xc80.U(Parameters.CSRRegisterAddrWidth)
+}
+
+class CSR extends Module {
+  val io = IO(new Bundle {
+    val reg_read_address_id = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val reg_write_enable_ex = Input(Bool())
+    val reg_write_address_ex = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val reg_write_data_ex = Input(UInt(Parameters.DataWidth))
+
+    val id_reg_read_data = Output(UInt(Parameters.DataWidth))
+
+    val clint_access_bundle = Flipped(new CSRDirectAccessBundle)
+  })
+
+  val mstatus = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mie = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mtvec = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mscratch = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mepc = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mcause = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val cycles = RegInit(UInt(64.W), 0.U)
+  val regLUT =
+    IndexedSeq(
+      CSRRegister.MSTATUS -> mstatus,
+      CSRRegister.MIE -> mie,
+      CSRRegister.MTVEC -> mtvec,
+      CSRRegister.MSCRATCH -> mscratch,
+      CSRRegister.MEPC -> mepc,
+      CSRRegister.MCAUSE -> mcause,
+      CSRRegister.CycleL -> cycles(31, 0),
+      CSRRegister.CycleH -> cycles(63, 32),
+    )
+  cycles := cycles + 1.U
+
+  // If the pipeline and the CLINT are going to read and write the CSR at the same time, let the pipeline write first.
+  // This is implemented in a single cycle by passing reg_write_data_ex to clint and writing the data from the CLINT to the CSR.
+  io.id_reg_read_data := MuxLookup(io.reg_read_address_id, 0.U, regLUT)
+
+  io.clint_access_bundle.mstatus := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MSTATUS, io.reg_write_data_ex, mstatus)
+  io.clint_access_bundle.mtvec := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MTVEC, io.reg_write_data_ex, mtvec)
+  io.clint_access_bundle.mcause := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MCAUSE, io.reg_write_data_ex, mcause)
+  io.clint_access_bundle.mepc := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MEPC, io.reg_write_data_ex, mepc)
+
+  when(io.clint_access_bundle.direct_write_enable) {
+    mstatus := io.clint_access_bundle.mstatus_write_data
+    mepc := io.clint_access_bundle.mepc_write_data
+    mcause := io.clint_access_bundle.mcause_write_data
+  }.elsewhen(io.reg_write_enable_ex) {
+    when(io.reg_write_address_ex === CSRRegister.MSTATUS) {
+      mstatus := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MEPC) {
+      mepc := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MCAUSE) {
+      mcause := io.reg_write_data_ex
+    }
+  }
+
+  when(io.reg_write_enable_ex) {
+    when(io.reg_write_address_ex === CSRRegister.MIE) {
+      mie := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MTVEC) {
+      mtvec := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MSCRATCH) {
+      mscratch := io.reg_write_data_ex
+    }
+  }
+}