path: root/src/models/lt_bus.h

#ifndef SYSC_PLAYGROUND_LT_BUS
#define SYSC_PLAYGROUND_LT_BUS

#include "utils/range.h"
#include "utils/sysc.h"
#include "utils/tlm_initiator_socket_tagged.h"
#include "utils/tlm_target_socket_tagged.h"
#include "utils/types.h"

#include <sysc/kernel/sc_event.h>

#include <algorithm>
#include <memory>
#include <vector>

// TLM bus lock extension.
//
// This extension is used to implemented the bus locking scheme.
// The protocol is as follows. Once an initiator sends a locked transaction,
// the bus will be locked by that initiator after all currently pending
// transactions are finished. The bus is locked until the locking initiator
// sends an unlocked transaction.
struct [[nodiscard]] bus_lock : tlm::tlm_extension<bus_lock> {
  bool is_lock{false};

  constexpr explicit bus_lock() = default;
  constexpr explicit bus_lock(const bus_lock&) = default;

  virtual tlm_extension_base* clone() const override {
    return new bus_lock(*this);
  }

  virtual void copy_from(const tlm_extension_base& ext) override {
    if (&ext == this) {
      // Copy from self, nop.
      return;
    }

    assert(typeid(this) == typeid(ext));
    const bus_lock& other = static_cast<const bus_lock&>(ext);

    is_lock = other.is_lock;
  }
};

class lt_bus : public sc_core::sc_module {
  using target_socket = tlm_target_socket_tagged<lt_bus>;
  using target_socket_ptr = std::unique_ptr<target_socket>;

  using initiator_socket = tlm_initiator_socket_tagged<lt_bus>;
  using initiator_socket_ptr = std::unique_ptr<initiator_socket>;

 public:
  explicit lt_bus(sc_core::sc_module_name nm)
      : sc_core::sc_module(std::move(nm)) {}

  // -- ATTACH BUS INITIATOR ---------------------------------------------------

  void attach_initiator(tlm::tlm_base_initiator_socket_b<>& init) {
    const usize id = m_initiators.size();
    const std::string name = "init" + std::to_string(id);
    {
      // Add current module on top of module stack for tlm sockets.
      scoped_push_hierarchy h(*this);

      // Add new target socket to connect BUS INITIATOR.
      m_initiators.push_back(std::make_unique<target_socket>(
          name.c_str(), id, this, &lt_bus::b_transport,
          &lt_bus::get_direct_mem_ptr, &lt_bus::transport_dbg));
    }

    // Bind sockets.
    auto& target = m_initiators.back();
    target->bind(init);
  }

  // -- ATTACH BUS TARGET ------------------------------------------------------

  void attach_target(tlm::tlm_base_target_socket_b<>& target,
                     u64 start,
                     u64 end) {
    assert(start <= end);
    const range addr{start, end};

    // Check if new range overlaps with any registered memory map range.
    for (const auto& mmap : m_mappings) {
      if (mmap.addr.overlaps(addr)) {
        std::fprintf(stderr,
                     "lt_bus: memory map conflict detected\n"
                     "old: %08lx - %08lx\n"
                     "new: %08lx - %08lx\n",
                     mmap.addr.start, mmap.addr.end, start, end);
        std::abort();
      }
    }

    const usize id = m_targets.size();
    const std::string name = "target" + std::to_string(id);
    {
      // Add current module on top of module stack for tlm sockets.
      scoped_push_hierarchy h(*this);

      // Add new initiator socket to connect BUS TARGET.
      m_targets.push_back(std::make_unique<initiator_socket>(
          name.c_str(), id, this, &lt_bus::invalidate_direct_mem_ptr));
    }

    // Bind sockets.
    auto& init = m_targets.back();
    init->bind(target);

    // Insert new mapping, id is equal to idx into socket vector.
    m_mappings.push_back({addr, id});
  }

  // -- SHOW_MMAP --------------------------------------------------------------

  void show_mmap() const {
    // Dump memory map.
    for (const auto& mmap : m_mappings) {
      std::printf("%08lx - %08lx :[%2ld] %s\n", mmap.addr.start, mmap.addr.end,
                  mmap.idx, m_targets[mmap.idx].get()->name());
    }
  }

 private:
  // -- TLM_BW_TRANSPORT_IF ----------------------------------------------------

  void invalidate_direct_mem_ptr(usize id,
                                 sc_dt::uint64 start,
                                 sc_dt::uint64 end) {
    assert(start <= end);

    for (const auto& mmap : m_mappings) {
      if (mmap.idx != id) {
        continue;
      }

      // Compute absolute start/end address based on memory map.
      const range abs_addr =
          compute_abs_mmap_address(range{start, end}, mmap.addr);

      for (auto& sock : m_initiators) {
        (*sock)->invalidate_direct_mem_ptr(abs_addr.start, abs_addr.end);
      }
    }
  }

  // -- TLM_FW_TRANSPORT_IF ----------------------------------------------------

  void b_transport(usize idx,
                   tlm::tlm_generic_payload& tx,
                   sc_core::sc_time& t) {
    if (const auto r = decode(tx)) {
      const auto do_tx = [&]() {
        const auto tx_start = tx.get_address();
        assert(r.start <= tx_start);

        tx.set_address(tx_start - r.start);
        (*r.sock)->b_transport(tx, t);
        tx.set_address(tx_start);
      };

      while (m_bl.is_locked && (m_bl.idx != idx)) {
        wait(m_bl.ev_no_pending_tx);
      }

      const auto* ext = tx.get_extension<bus_lock>();
      if (ext && ext->is_lock) {
        assert(!m_bl.is_locked);

        m_bl.is_locked = true;
        m_bl.idx = idx;

        if (m_bl.pending_tx) {
          wait(m_bl.ev_no_pending_tx);
        }
        assert(m_bl.pending_tx == 0);

        // Invalidate DMI pointers for the whole address space. This forces all
        // initiators on the slow path and through the bus, which can than
        // enforce the exclusive access.
        for (auto& sock : m_initiators) {
          (*sock)->invalidate_direct_mem_ptr(0, -1ull);
        }

        do_tx();
        assert(m_bl.pending_tx == 0);
      } else {
        assert(!m_bl.is_locked || (m_bl.is_locked && m_bl.idx == idx));

        m_bl.pending_tx++;
        do_tx();
        m_bl.pending_tx--;

        if (m_bl.is_locked && m_bl.idx == idx) {
          assert(m_bl.pending_tx == 0);
          m_bl.is_locked = false;
        }

        if (m_bl.pending_tx == 0) {
          m_bl.ev_no_pending_tx.notify(sc_core::SC_ZERO_TIME);
        }
      }
    } else {
      tx.set_response_status(tlm::TLM_ADDRESS_ERROR_RESPONSE);
    }
  }

  bool get_direct_mem_ptr(usize,
                          tlm::tlm_generic_payload& tx,
                          tlm::tlm_dmi& dmi) {
    if (m_bl.is_locked) {
      return false;
    }

    if (const auto r = decode(tx)) {
      const auto tx_start = tx.get_address();
      assert(r.start <= tx_start);

      tx.set_address(tx_start - r.start);
      const bool ok = (*r.sock)->get_direct_mem_ptr(tx, dmi);
      tx.set_address(tx_start);

      // Early return, dmi request failed, no need to fixup dmi addresses.
      if (!ok) {
        return false;
      }

      // Compute absolute start/end address based on memory map.
      const range abs_addr = compute_abs_mmap_address(
          range{dmi.get_start_address(), dmi.get_end_address()},
          range{r.start, r.end});

      // Update dmi payload with absolute addresses.
      dmi.set_start_address(abs_addr.start);
      dmi.set_end_address(abs_addr.end);

      return true;
    }
    return false;
  }

  unsigned int transport_dbg(usize, tlm::tlm_generic_payload& tx) {
    unsigned int ret = 0;
    if (const auto r = decode(tx)) {
      const auto tx_start = tx.get_address();
      assert(r.start <= tx_start);

      tx.set_address(tx_start - r.start);
      ret = (*r.sock)->transport_dbg(tx);
      tx.set_address(tx_start);
    }
    return ret;
  }

  // -- DECODE BUS TARGET ------------------------------------------------------

  struct decode_result {
    initiator_socket* sock{nullptr};
    u64 start{0ull};
    u64 end{0ull};

    constexpr explicit operator bool() const {
      return sock != nullptr;
    }
  };

  decode_result decode(range addr) const {
    for (const auto& mmap : m_mappings) {
      if (mmap.addr.contains(addr)) {
        return {m_targets[mmap.idx].get(), mmap.addr.start, mmap.addr.end};
      }
    }
    return {};
  }

  decode_result decode(const tlm::tlm_generic_payload& tx) const {
    const u64 start = tx.get_address();
    const u64 end = start + tx.get_data_length() - 1;
    return decode(range{start, end});
  }

  // -- COMPUTE ABSOLUTE MEMORY MAP ADDRESS ------------------------------------

  static range compute_abs_mmap_address(range rel, range mmap) {
    // Compute absolute start address.
    const sc_dt::uint64 abs_start = mmap.start + rel.start;
    // Start address must be in bounds of the memory map mapping.
    assert(abs_start <= mmap.end);

    // Compute absolute end address. Limit by memory map if range exceeded.
    const auto comp_abs_end = [&mmap](sc_dt::uint64 abs_end) -> sc_dt::uint64 {
      if (abs_end > mmap.end /* exceeds mapping */ ||
          abs_end < mmap.start /* wraps around */) {
        return mmap.end;
      }
      return abs_end;
    };
    const sc_dt::uint64 abs_end = comp_abs_end(mmap.start + rel.end);

    return range{abs_start, abs_end};
  }

  // -- SC_MODULE CALLBACKS ----------------------------------------------------

  virtual void start_of_simulation() override {
    // Sort memory mappings by start address.
    std::sort(m_mappings.begin(), m_mappings.end(),
              [](const mapping& lhs, const mapping& rhs) {
                return lhs.addr.start < rhs.addr.start;
              });
  }

  // -- LOCAL CLASSES ----------------------------------------------------------

  struct mapping {
    range addr;
    usize idx;
  };

  // -- MEMBER -----------------------------------------------------------------

  // TARGET sockets to bind BUS INITIATORS against.
  std::vector<target_socket_ptr> m_initiators;
  // INITIATOR sockets to bind BUS TARGET against.
  std::vector<initiator_socket_ptr> m_targets;
  // Address range mappings to BUS TARGETs (m_tragets).
  std::vector<mapping> m_mappings;

  struct bus_lock_state {
    bool is_locked{false};
    usize idx{0};
    usize pending_tx{0};
    sc_core::sc_event ev_no_pending_tx;
  } m_bl;
};

#endif