src/dev/riscv/clint.hh

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 * Copyright (c) 2021 Huawei International
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 *
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 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
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 * this software without specific prior written permission.
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#ifndef __DEV_RISCV_CLINT_HH__
#define __DEV_RISCV_CLINT_HH__

#include "arch/riscv/interrupts.hh"
#include "dev/intpin.hh"
#include "dev/io_device.hh"
#include "dev/mc146818.hh"
#include "dev/reg_bank.hh"
#include "mem/packet.hh"
#include "mem/packet_access.hh"
#include "params/Clint.hh"
#include "sim/system.hh"

namespace gem5
{

using namespace RiscvISA;

/**
 * NOTE:
 * This implementation of CLINT is based on
 * the SiFive U54MC datasheet:
 * https://sifive.cdn.prismic.io/sifive/fab000f6-
 * 0e07-48d0-9602-e437d5367806_sifive_U54MC_rtl_
 * full_20G1.03.00_manual.pdf
 */

/**
 * Future improvement of the model can check
 * the current privilege mode and enforce
 * access control.
 */
class Clint : public BasicPioDevice
{
  // Params
  protected:
    System *system;
    int nThread;
    IntSinkPin<Clint> signal;

  public:
    typedef ClintParams Params;
    Clint(const Params &params);

  // RTC Signal
  public:
    /**
     * Timer tick callback. Separated from RTC class
     * for easier implementation of a separate RTC
     * PioDevice.
     */
    void raiseInterruptPin(int id);
    void lowerInterruptPin(int id) {}

  // Register bank
  public:

    /**
     * MMIO Registers
     * 0x0000 - 0x3FFF: msip (write-through to misc reg file)
     * ...:             reserved[0]
     * 0x4000 - 0xBFF7: mtimecmp
     * ...:             reserved[1]
     * 0xBFF8:          mtime (read-only)
     */
    class ClintRegisters: public RegisterBankLE
    {
      public:
        const Addr mtimecmpStart = 0x4000;
        const Addr mtimeStart = 0xBFF8;
        const Addr maxBankSize = 0xC000;

        std::vector<Register32> msip;
        std::vector<Register64> mtimecmp;
        Register64 mtime = {"mtime", 0};
        std::vector<RegisterRaz> reserved;

        ClintRegisters(const std::string &name, Addr base, Clint* clint) :
          RegisterBankLE(name, base),
          clint(clint) {}

        Clint *clint;

        void init();

    } registers;

    using Register32 = ClintRegisters::Register32;

    uint32_t readMSIP(Register32& reg, const int thread_id);
    void writeMSIP(Register32& reg, const uint32_t& data, const int thread_id);

  // External API
  public:
    /**
     * PioDevice interface functions
     */
    Tick read(PacketPtr pkt) override;
    Tick write(PacketPtr pkt) override;

    /**
     * SimObject functions
     */
    void init() override;
    Port & getPort(const std::string &if_name,
                   PortID idx=InvalidPortID) override;
    void serialize(CheckpointOut &cp) const override;
    void unserialize(CheckpointIn &cp) override;

};

} // namespace gem5

#endif // __DEV_RISCV_CLINT_HH__