// See LICENSE for license details.

package rocket

import Chisel._
import Util._
import Instructions._
import Node._
import uncore._
import scala.math._

class MStatus extends Bundle {
  val sd = Bool()
  val zero6 = UInt(width = 19)
  val ha = UInt(width = 4)
  val sa = UInt(width = 4)
  val ua = UInt(width = 4)
  val zero5 = UInt(width = 1)
  val xs = UInt(width = 2)
  val fs = UInt(width = 2)
  val mtie = Bool()
  val htie = Bool()
  val stie = Bool()
  val zero4 = UInt(width = 1)
  val vm = UInt(width = 4)
  val zero3 = UInt(width = 1)
  val mprv = UInt(width = 2)
  val zero2 = UInt(width = 3)
  val prv2 = UInt(width = 2)
  val ie2 = Bool()
  val prv1 = UInt(width = 2)
  val ie1 = Bool()
  val prv = UInt(width = 2)
  val ie = Bool()
  val msip = Bool()
  val hsip = Bool()
  val ssip = Bool()
  val zero1 = UInt(width = 1)
}

class SStatus extends Bundle {
  val sd = Bool()
  val zero6 = UInt(width = 32)
  val xs = UInt(width = 2)
  val fs = UInt(width = 2)
  val tip = Bool()
  val zero5 = UInt(width = 1)
  val tie = Bool()
  val zero4 = UInt(width = 4)
  val ua = UInt(width = 4)
  val zero3 = UInt(width = 7)
  val ps = Bool()
  val pie = UInt(width = 1)
  val zero2 = UInt(width = 2)
  val ie = Bool()
  val zero1 = UInt(width = 2)
  val sip = Bool()
  val zero0 = UInt(width = 1)
}

object CSR
{
  // commands
  val SZ = 3
  val X = UInt.DC(SZ)
  val N = UInt(0,SZ)
  val W = UInt(1,SZ)
  val S = UInt(2,SZ)
  val C = UInt(3,SZ)
  val I = UInt(4,SZ)
  val R = UInt(5,SZ)
}

class CSRFileIO extends CoreBundle {
  val host = new HTIFIO
  val rw = new Bundle {
    val addr = UInt(INPUT, 12)
    val cmd = Bits(INPUT, CSR.SZ)
    val rdata = Bits(OUTPUT, xLen)
    val wdata = Bits(INPUT, xLen)
  }

  val csr_replay = Bool(OUTPUT)
  val csr_xcpt = Bool(OUTPUT)

  val status = new MStatus().asOutput
  val ptbr = UInt(OUTPUT, paddrBits)
  val evec = UInt(OUTPUT, vaddrBits+1)
  val exception = Bool(INPUT)
  val retire = UInt(INPUT, log2Up(1+retireWidth))
  val uarch_counters = Vec.fill(16)(UInt(INPUT, log2Up(1+retireWidth)))
  val cause = UInt(INPUT, xLen)
  val mbadaddr_wen = Bool(INPUT)
  val pc = SInt(INPUT, vaddrBits+1)
  val sret = Bool(INPUT)
  val fatc = Bool(OUTPUT)
  val time = UInt(OUTPUT, xLen)
  val fcsr_rm = Bits(OUTPUT, FPConstants.RM_SZ)
  val fcsr_flags = Valid(Bits(width = FPConstants.FLAGS_SZ)).flip
  val rocc = new RoCCInterface().flip
  val interrupt = Bool(OUTPUT)
  val interrupt_cause = UInt(OUTPUT, xLen)
}

class CSRFile extends CoreModule
{
  val io = new CSRFileIO
 
  val reg_mstatus = Reg(new MStatus)
  val reg_mepc = Reg(SInt(width = vaddrBits+1))
  val reg_mcause = Reg(Bits(width = xLen))
  val reg_mbadaddr = Reg(SInt(width = vaddrBits+1))
  val reg_mscratch = Reg(Bits(width = xLen))

  val reg_sepc = Reg(SInt(width = vaddrBits+1))
  val reg_scause = Reg(Bits(width = xLen))
  val reg_sbadaddr = Reg(SInt(width = vaddrBits+1))
  val reg_sscratch = Reg(Bits(width = xLen))
  val reg_stvec = Reg(SInt(width = vaddrBits))
  val reg_stimecmp = Reg(Bits(width = 32))
  val reg_sptbr = Reg(UInt(width = paddrBits))

  val reg_tohost = Reg(init=Bits(0, xLen))
  val reg_fromhost = Reg(init=Bits(0, xLen))
  val reg_stats = Reg(init=Bool(false))
  val reg_time = WideCounter(xLen)
  val reg_instret = WideCounter(xLen, io.retire)
  val reg_uarch_counters = io.uarch_counters.map(WideCounter(xLen, _))
  val reg_fflags = Reg(UInt(width = 5))
  val reg_frm = Reg(UInt(width = 3))

  val r_irq_timer = Reg(init=Bool(false))
  val irq_rocc = Bool(!params(BuildRoCC).isEmpty) && io.rocc.interrupt

  io.interrupt_cause := 0
  io.interrupt := io.interrupt_cause(xLen-1)
  def checkInterrupt(max_priv: UInt, cond: Bool, num: Int) = {
    when (cond && (reg_mstatus.prv < max_priv || reg_mstatus.prv === max_priv && reg_mstatus.ie)) {
      io.interrupt_cause := UInt((BigInt(1) << (xLen-1)) + num)
    }
  }

  checkInterrupt(PRV_S, r_irq_timer, 0)
  checkInterrupt(PRV_S, reg_mstatus.ssip, 1)
  checkInterrupt(PRV_M, reg_mstatus.msip, 1)
  checkInterrupt(PRV_M, reg_fromhost != 0, 2)
  checkInterrupt(PRV_M, irq_rocc, 3)

  val system_insn = io.rw.cmd === CSR.I
  val cpu_ren = io.rw.cmd != CSR.N && !system_insn

  val host_pcr_req_valid = Reg(Bool()) // don't reset
  val host_pcr_req_fire = host_pcr_req_valid && !cpu_ren
  val host_pcr_rep_valid = Reg(Bool()) // don't reset
  val host_pcr_bits = Reg(io.host.pcr_req.bits)
  io.host.pcr_req.ready := !host_pcr_req_valid && !host_pcr_rep_valid
  io.host.pcr_rep.valid := host_pcr_rep_valid
  io.host.pcr_rep.bits := host_pcr_bits.data
  when (io.host.pcr_req.fire()) {
    host_pcr_req_valid := true
    host_pcr_bits := io.host.pcr_req.bits
  }
  when (host_pcr_req_fire) {
    host_pcr_req_valid := false
    host_pcr_rep_valid := true
    host_pcr_bits.data := io.rw.rdata
  }
  when (io.host.pcr_rep.fire()) { host_pcr_rep_valid := false }
  
  io.host.debug_stats_pcr := reg_stats // direct export up the hierarchy

  val addr = Mux(cpu_ren, io.rw.addr, host_pcr_bits.addr)
  val decoded_addr = Map((
    for ((v, i) <- CSRs.all.zipWithIndex)
      yield v -> (addr === CSRs.all(i))):_*)

  val addr_valid = decoded_addr.values.reduce(_||_)
  val fp_csr = decoded_addr(CSRs.fflags) || decoded_addr(CSRs.frm) || decoded_addr(CSRs.fcsr)
  val csr_addr_priv = io.rw.addr(9,8)
  val priv_sufficient = reg_mstatus.prv >= csr_addr_priv
  val read_only = io.rw.addr(11,10).andR
  val cpu_wen = cpu_ren && io.rw.cmd != CSR.R && priv_sufficient
  val wen = cpu_wen && !read_only || host_pcr_req_fire && host_pcr_bits.rw
  val wdata = Mux(io.rw.cmd === CSR.W, io.rw.wdata,
              Mux(io.rw.cmd === CSR.C, io.rw.rdata & ~io.rw.wdata,
              Mux(io.rw.cmd === CSR.S, io.rw.rdata | io.rw.wdata,
              host_pcr_bits.data)))

  val opcode = io.rw.addr(3,0)
  // The following comparison is meant to be opcode === SFENCE_VM(23,20). But
  // FOR SOME FUCKING REASON, extracting SFENCE_VM(23,20) gives 3, not 4.
  val insn_sfence_vm = opcode === 4 && system_insn && priv_sufficient
  val insn_redirect_trap = opcode === MRTS(23,20) && system_insn && priv_sufficient
  val insn_ret = opcode === SRET(23,20) /* or H/MRET */ && io.rw.addr(1) && system_insn && priv_sufficient
  val insn_break = opcode === SBREAK(23,20) && io.rw.addr(0) && system_insn && priv_sufficient
  val insn_call = opcode === SCALL(23,20) /* or H/MCALL */ && system_insn && priv_sufficient

  val csr_xcpt = (cpu_wen && read_only) ||
    (cpu_ren && (!priv_sufficient || !addr_valid || fp_csr && !io.status.fs.orR)) ||
    (system_insn && !priv_sufficient) ||
    insn_call || insn_break

  val mtvec = reg_mstatus.prv << 6
  io.fatc := insn_sfence_vm
  io.evec := Mux(io.exception || csr_xcpt, mtvec.zext,
             Mux(insn_redirect_trap, reg_stvec,
             Mux(reg_mstatus.prv(1), reg_mepc, reg_sepc))).toUInt
  io.ptbr := reg_sptbr
  io.csr_xcpt := csr_xcpt || insn_redirect_trap || insn_ret /* sort of a lie */
  io.status := reg_mstatus
  io.status.fs := reg_mstatus.fs.orR.toSInt // either off or dirty (no clean/initial support yet)
  io.status.xs := reg_mstatus.xs.orR.toSInt // either off or dirty (no clean/initial support yet)
  io.status.sd := reg_mstatus.xs.orR || reg_mstatus.fs.orR

  when (io.exception || csr_xcpt) {
    reg_mstatus.ie := false
    reg_mstatus.prv := PRV_M
    reg_mstatus.mprv := PRV_M
    reg_mstatus.prv1 := reg_mstatus.prv
    reg_mstatus.ie1 := reg_mstatus.ie
    reg_mstatus.prv2 := reg_mstatus.prv1
    reg_mstatus.ie2 := reg_mstatus.ie1

    reg_mepc := io.pc
    reg_mcause := io.cause
    when (csr_xcpt) {
      reg_mcause := Causes.illegal_instruction
      when (insn_break) { reg_mcause := Causes.breakpoint }
      when (insn_call) { reg_mcause := Causes.scall + csr_addr_priv }
    }

    reg_mbadaddr := io.pc
    when (io.cause === Causes.fault_load || io.cause === Causes.misaligned_load ||
         io.cause === Causes.fault_store || io.cause === Causes.misaligned_store) {
      val wdata = io.rw.wdata
      val (upper, lower) = Split(wdata, vaddrBits)
      val sign = Mux(lower.toSInt < SInt(0), upper.andR, upper.orR)
      reg_mbadaddr := Cat(sign, lower).toSInt
    }
  }
  
  when (insn_ret) {
    reg_mstatus.ie := reg_mstatus.ie1
    reg_mstatus.prv := reg_mstatus.prv1
    reg_mstatus.prv1 := reg_mstatus.prv2
    reg_mstatus.ie1 := reg_mstatus.ie2
    reg_mstatus.prv2 := PRV_U
    reg_mstatus.ie2 := true
  }
  
  when (insn_redirect_trap) {
    reg_mstatus.prv := PRV_S
    reg_sbadaddr := reg_mbadaddr
    reg_scause := reg_mcause
    reg_sepc := reg_mepc
  }

  assert(PopCount(insn_ret :: insn_redirect_trap :: io.exception :: csr_xcpt :: io.csr_replay :: Nil) <= 1, "these conditions must be mutually exclusive")

  when (reg_time(reg_stimecmp.getWidth-1,0) === reg_stimecmp) {
    r_irq_timer := true
  }

  io.time := reg_time
  io.host.ipi_req.valid := cpu_wen && decoded_addr(CSRs.send_ipi)
  io.host.ipi_req.bits := io.rw.wdata
  io.csr_replay := io.host.ipi_req.valid && !io.host.ipi_req.ready

  when (host_pcr_req_fire && !host_pcr_bits.rw && decoded_addr(CSRs.tohost)) { reg_tohost := UInt(0) }

  val read_mstatus = io.status.toBits
  val read_sstatus = new SStatus
  read_sstatus := new SStatus().fromBits(read_mstatus) // sstatus mostly overlaps mstatus
  read_sstatus.zero0 := 0
  read_sstatus.zero1 := 0
  read_sstatus.zero2 := 0
  read_sstatus.zero3 := 0
  read_sstatus.zero4 := 0
  read_sstatus.zero5 := 0
  read_sstatus.ua := io.status.ua
  read_sstatus.tip := r_irq_timer

  val read_mapping = collection.mutable.LinkedHashMap[Int,Bits](
    CSRs.fflags -> (if (!params(BuildFPU).isEmpty) reg_fflags else UInt(0)),
    CSRs.frm -> (if (!params(BuildFPU).isEmpty) reg_frm else UInt(0)),
    CSRs.fcsr -> (if (!params(BuildFPU).isEmpty) Cat(reg_frm, reg_fflags) else UInt(0)),
    CSRs.cycle -> reg_time,
    CSRs.time -> reg_time,
    CSRs.scycle -> reg_time,
    CSRs.stime -> reg_time,
    CSRs.instret -> reg_instret,
    CSRs.sinstret -> reg_instret,
    CSRs.mstatus -> read_mstatus,
    CSRs.mscratch -> reg_mscratch,
    CSRs.mepc -> reg_mepc,
    CSRs.mbadaddr -> reg_mbadaddr,
    CSRs.mcause -> reg_mcause,
    CSRs.sstatus -> read_sstatus.toBits,
    CSRs.sscratch -> reg_sscratch,
    CSRs.sepc -> reg_sepc,
    CSRs.scause -> reg_scause,
    CSRs.sbadaddr -> reg_sbadaddr,
    CSRs.sptbr -> reg_sptbr,
    CSRs.sasid -> UInt(0),
    CSRs.stimecmp -> reg_stimecmp,
    CSRs.stvec -> reg_stvec,
    CSRs.hartid -> io.host.id,
    CSRs.stats -> reg_stats,
    CSRs.tohost -> reg_tohost,
    CSRs.fromhost -> reg_fromhost)

  for (i <- 0 until reg_uarch_counters.size)
    read_mapping += (CSRs.uarch0 + i) -> reg_uarch_counters(i)

  io.rw.rdata := Mux1H(for ((k, v) <- read_mapping) yield decoded_addr(k) -> v)

  io.fcsr_rm := reg_frm
  when (io.fcsr_flags.valid) {
    reg_fflags := reg_fflags | io.fcsr_flags.bits
  }

  when (wen) {
    when (decoded_addr(CSRs.mstatus)) {
      val new_mstatus = new MStatus().fromBits(wdata)
      reg_mstatus.ssip := new_mstatus.ssip
      reg_mstatus.msip := new_mstatus.msip
      reg_mstatus.stie := new_mstatus.stie
      reg_mstatus.ie := new_mstatus.ie
      reg_mstatus.ie1 := new_mstatus.ie1
      reg_mstatus.ie2 := new_mstatus.ie2
      when (new_mstatus.mprv != PRV_H) { reg_mstatus.mprv := new_mstatus.mprv }
      when (new_mstatus.prv != PRV_H) { reg_mstatus.prv := new_mstatus.prv }
      when (new_mstatus.prv1 != PRV_H) { reg_mstatus.prv1 := new_mstatus.prv1 }
      when (new_mstatus.prv2 != PRV_H) { reg_mstatus.prv2 := new_mstatus.prv2 }
      if (params(UseVM)) when (new_mstatus.vm === 0 || new_mstatus.vm === 5) { reg_mstatus.vm := new_mstatus.vm }
      if (!params(BuildFPU).isEmpty) reg_mstatus.fs := new_mstatus.fs
      if (!params(BuildRoCC).isEmpty) reg_mstatus.xs := new_mstatus.xs
    }
    when (decoded_addr(CSRs.sstatus)) {
      val new_sstatus = new SStatus().fromBits(wdata)
      reg_mstatus.ssip := new_sstatus.sip
      reg_mstatus.stie := new_sstatus.tie
      reg_mstatus.ie := new_sstatus.ie
      reg_mstatus.ie1 := new_sstatus.pie
      reg_mstatus.prv1 := Mux(new_sstatus.ps, PRV_S, PRV_U)
      if (!params(BuildFPU).isEmpty) reg_mstatus.fs := new_sstatus.fs
      if (!params(BuildRoCC).isEmpty) reg_mstatus.xs := new_sstatus.xs
    }
    when (decoded_addr(CSRs.fflags))   { reg_fflags := wdata }
    when (decoded_addr(CSRs.frm))      { reg_frm := wdata }
    when (decoded_addr(CSRs.fcsr))     { reg_fflags := wdata; reg_frm := wdata >> reg_fflags.getWidth }
    when (decoded_addr(CSRs.mepc))     { reg_mepc := wdata(vaddrBits,0).toSInt }
    when (decoded_addr(CSRs.mscratch)) { reg_mscratch := wdata }
    when (decoded_addr(CSRs.mcause))   { reg_mcause := wdata & UInt((BigInt(1) << (xLen-1)) + 31) /* only implement 5 LSBs and MSB */ }
    when (decoded_addr(CSRs.mbadaddr)) { reg_mbadaddr := wdata }
    when (decoded_addr(CSRs.sepc))     { reg_sepc := wdata(vaddrBits,0).toSInt }
    when (decoded_addr(CSRs.stvec))    { reg_stvec := wdata(vaddrBits-1,0).toSInt }
    when (decoded_addr(CSRs.scycle))   { reg_time := wdata.toUInt }
    when (decoded_addr(CSRs.stime))    { reg_time := wdata.toUInt }
    when (decoded_addr(CSRs.sinstret)) { reg_instret := wdata.toUInt }
    when (decoded_addr(CSRs.stimecmp)) { reg_stimecmp := wdata(31,0).toUInt; r_irq_timer := Bool(false) }
    when (decoded_addr(CSRs.fromhost)) { when (reg_fromhost === UInt(0) || !host_pcr_req_fire) { reg_fromhost := wdata } }
    when (decoded_addr(CSRs.tohost))   { when (reg_tohost === UInt(0) || host_pcr_req_fire) { reg_tohost := wdata } }
    when (decoded_addr(CSRs.sscratch)) { reg_sscratch := wdata }
    when (decoded_addr(CSRs.sptbr))    { reg_sptbr := Cat(wdata(paddrBits-1, pgIdxBits), Bits(0, pgIdxBits)).toUInt }
    when (decoded_addr(CSRs.stats))    { reg_stats := wdata(0) }
  }

  io.host.ipi_rep.ready := true
  when (io.host.ipi_rep.valid) { reg_mstatus.msip := true }

  when(this.reset) {
    reg_mstatus.zero1 := 0
    reg_mstatus.ssip := false
    reg_mstatus.hsip := false
    reg_mstatus.msip := false
    reg_mstatus.ie := false
    reg_mstatus.prv := PRV_M
    reg_mstatus.ie1 := false
    reg_mstatus.prv1 := PRV_S
    reg_mstatus.ie2 := false
    reg_mstatus.prv2 := PRV_S
    reg_mstatus.mprv := PRV_M
    reg_mstatus.zero2 := 0
    reg_mstatus.vm := 0
    reg_mstatus.zero3 := 0
    reg_mstatus.stie := false
    reg_mstatus.htie := false
    reg_mstatus.mtie := false
    reg_mstatus.fs := 0
    reg_mstatus.xs := 0
    reg_mstatus.zero4 := 0
    reg_mstatus.ua := 4
    reg_mstatus.sa := 4
    reg_mstatus.ha := 0
    reg_mstatus.zero5 := 0
    reg_mstatus.sd := false
  }
}