xref: /gem5/src/systemc/ext/tlm_core/2/interfaces/fw_bw_ifs.hh

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#ifndef __SYSTEMC_EXT_TLM_CORE_2_INTERFACES_FW_BW_IFS_HH__
#define __SYSTEMC_EXT_TLM_CORE_2_INTERFACES_FW_BW_IFS_HH__

#include <systemc>

#include "tlm_core/2/generic_payload/generic_payload.hh"
#include "tlm_core/2/interfaces/dmi.hh"

namespace tlm
{

enum tlm_sync_enum { TLM_ACCEPTED, TLM_UPDATED, TLM_COMPLETED };

////////////////////////////////////////////////////////////////////////////
// Basic interfaces
////////////////////////////////////////////////////////////////////////////
template <typename TRANS=tlm_generic_payload, typename PHASE=tlm_phase>
class tlm_fw_nonblocking_transport_if : public virtual sc_core::sc_interface
{
  public:
    virtual tlm_sync_enum nb_transport_fw(TRANS &trans, PHASE &phase,
                                          sc_core::sc_time& t) = 0;
};

template <typename TRANS=tlm_generic_payload, typename PHASE=tlm_phase>
class tlm_bw_nonblocking_transport_if : public virtual sc_core::sc_interface
{
  public:
    virtual tlm_sync_enum nb_transport_bw(TRANS &trans, PHASE &phase,
                                          sc_core::sc_time &t) = 0;
};

template <typename TRANS=tlm_generic_payload>
class tlm_blocking_transport_if : public virtual sc_core::sc_interface
{
  public:
    virtual void b_transport(TRANS &trans, sc_core::sc_time &t) = 0;
};

//////////////////////////////////////////////////////////////////////////
// DMI interfaces for getting and invalidating DMI pointers:
//////////////////////////////////////////////////////////////////////////

// The semantics of the forward interface are as follows:
//
// - An initiator that wants to get direct access to a target's memory region
//   can call the get_direct_mem_ptr method with the 'trans' parameter set to
//   the address that it wants to gain access to. It sets the trans.m_command
//   to specify if the initiator intended use (read or write)
//   to the target's DMI region. The initiator is responsible for calling the
//   method with a freshly initialized tlm_dmi object either by using a newly
//   constructed object, or by calling an existing object's init() method.
// - Although a reference to a complete 'TRANS' type is passed to the get_
//   direct_mem_ptr call, only the address command, and extension fields are of
//   interest in most cases.
// - Read and write ranges are not necessarily identical. If they are, a target
//   can specify that the range is valid for all accesses with the tlm_data
//   m_type attribute in the.
// - The interconnect, if any, needs to decode the address and forward the
//   call to the corresponding target. It needs to handle the address exactly
//   as the target would expect on a transaction call, e.g. mask the address
//   according to the target's address width.
// - If the target supports DMI access for the given address, it sets the
//   data fields in the DMI struct and returns true.
// - If a target does not support DMI access it needs to return false.
//   The target can either set the correct address range in the DMI struct
//   to indicate the memory region where DMI is disallowed, or it can specify
//   the complete address range if it doesn't know it's memory range. In this
//   case the interconnect is responsible for clipping the address range to
//   the correct range that the target serves.
// - The interconnect must always translate the addresses to the initiator's
//   address space. This must be the inverse operation of what the
//   interconnect needed to do when forwarding the call. In case the
//   component wants to change any member of the tlm_dmi object, e.g. for
//   its own latency to the target's latency, it must only do so *after* the
//   target has been called. The target is always allowed to overwrite all
//   values in the tlm_dmi object.
// - In case the slave returned with an invalid region the bus/interconnect
//   must fill in the complete address region for the particular slave in the
//   DMI data structure.
//
// DMI hint optimization:
//
// Initiators may use the DMI hint in the tlm_generic_payload to avoid
// unnecessary DMI attempts. The recommended sequence of interface
// method calls would be:
//
// - The initiator first tries to check if it has a valid DMI region for the
//   address that it wants to access next.
// - If not, it performs a normal transaction.
// - If the DMI hint in this transaction is true, the initiator can try and
//   get the DMI region.
//
// Note that the DMI hint optimization is completely optional and every
// initiator model is free to ignore the DMI hint. However, a target is
// required to set the DMI hint to true if a DMI request on the given address
// with the given transaction type (read or write) would have succeeded.

template <typename TRANS=tlm_generic_payload>
class tlm_fw_direct_mem_if : public virtual sc_core::sc_interface
{
  public:
    virtual bool get_direct_mem_ptr(TRANS &trans, tlm_dmi &dmi_data) = 0;
};

// The semantics of the backwards call is as follows:
//
// - An interconnect component or a target is required to invalidate all
//   affected DMI regions whenever any change in the regions take place.
//   The exact rule is that a component must invalidate all those DMI regions
//   that it already reported, if it would answer the same DMI request
//   with any member of the tlm_dmi data structure set differently.
// - An interconnect component must forward the invalidate_direct_mem_ptr call
//   to all initiators that could potentially have a DMI pointer to the region
//   specified in the method arguments. A safe implementation is to call
//   every attached initiator.
// - An interconnect component must transform the address region of an
//   incoming invalidate_direct_mem_ptr to the corresponding address space
//   for the initiators. Basically, this is the same address transformation
//   that the interconnect does on the DMI ranges on the forward direction.
// - Each initiator must check if it has a pointer to the given region and
//   throw this away. It is recommended that the initiator throws away all DMI
//   regions that have any overlap with the given regions, but this is not a
//   hard requirement.
//
// - A full DMI pointer invalidation, e.g. for a bus remap can be signaled
//   by setting the range: 0x0 - 0xffffffffffffffffull = (sc_dt::uint64)-1
// - An initiator must throw away all DMI pointers in this case.
//
// - Under no circumstances a model is allowed to call the get_direct_mem_ptr
//   from within the invalidate_direct_mem_ptr method, directly or indirectly.
//
class tlm_bw_direct_mem_if : public virtual sc_core::sc_interface
{
  public:
    virtual void invalidate_direct_mem_ptr(sc_dt::uint64 start_range,
                                           sc_dt::uint64 end_range) = 0;
};

/////////////////////////////////////////////////////////////////////
// debug interface for memory access
/////////////////////////////////////////////////////////////////////
//
// This interface can be used to gain access to a targets memory or registers
// in a non-intrusive manner. No side effects, waits or event notifications
// must happen in the course of the method.
//
// Semantics:
// - The initiator calls the transport_dbg method with transaction 'trans' as
//   argument. The commonly used parts of trans for debug are:
//   . address: The start address that it wants to peek or poke.
//   . length:  The number of bytes that it requests to read or write.
//   . command: Indicates a read or write access.
//   . data:    A pointer to the initiator-allocated data buffer, which must
//              be at least num_bytes large. The data is always organized in
//              the endianness of the machine.
//   . extensions: Any extension that could affect the transaction.
// - The interconnect, if any, will decode the address and forward the call to
//   the appropriate target.
// - The target must return the number of successfully transmitted bytes, where
//   this number must be <= num_bytes. Thus, a target can safely return 0 if it
//   does not support debug transactions.
//
template <typename TRANS=tlm_generic_payload>
class tlm_transport_dbg_if : public virtual sc_core::sc_interface
{
  public:
    // The return value of defines the number of bytes successfully
    // transferred.
    virtual unsigned int transport_dbg(TRANS &trans) = 0;
};

////////////////////////////////////////////////////////////////////////////
// Combined interfaces
////////////////////////////////////////////////////////////////////////////

struct tlm_base_protocol_types
{
    typedef tlm_generic_payload tlm_payload_type;
    typedef tlm_phase tlm_phase_type;
};

// The forward interface:
template <typename TYPES=tlm_base_protocol_types>
class tlm_fw_transport_if :
    public virtual tlm_fw_nonblocking_transport_if<
        typename TYPES::tlm_payload_type, typename TYPES::tlm_phase_type>,
    public virtual tlm_blocking_transport_if<typename TYPES::tlm_payload_type>,
    public virtual tlm_fw_direct_mem_if<typename TYPES::tlm_payload_type>,
    public virtual tlm_transport_dbg_if<typename TYPES::tlm_payload_type>
{};

// The backward interface:
template <typename TYPES=tlm_base_protocol_types>
class tlm_bw_transport_if :
    public virtual tlm_bw_nonblocking_transport_if<
        typename TYPES::tlm_payload_type, typename TYPES::tlm_phase_type>,
    public virtual tlm_bw_direct_mem_if
{};

} // namespace tlm

#endif /* __SYSTEMC_EXT_TLM_CORE_2_INTERFACES_FW_BW_IFS_HH__ */