tlm_quantumkeeper.h revision 13511 
1/*****************************************************************************
2
3  Licensed to Accellera Systems Initiative Inc. (Accellera) under one or
4  more contributor license agreements.  See the NOTICE file distributed
5  with this work for additional information regarding copyright ownership.
6  Accellera licenses this file to you under the Apache License, Version 2.0
7  (the "License"); you may not use this file except in compliance with the
8  License.  You may obtain a copy of the License at
9
10    http://www.apache.org/licenses/LICENSE-2.0
11
12  Unless required by applicable law or agreed to in writing, software
13  distributed under the License is distributed on an "AS IS" BASIS,
14  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
15  implied.  See the License for the specific language governing
16  permissions and limitations under the License.
17
18 *****************************************************************************/
19
20// 20-Mar-2009  John Aynsley  Add set_and_sync() method
21
22
23#ifndef __TLM_QUANTUMKEEPER_H__
24#define __TLM_QUANTUMKEEPER_H__
25
26#include "tlm_core/tlm_2/tlm_quantum/tlm_global_quantum.h"
27
28namespace tlm_utils {
29
30  //
31  // tlm_quantumkeeper class
32  //
33  // The tlm_quantumkeeper class is used to keep track of the local time in
34  // an initiator (how much it has run ahead of the SystemC time), to
35  // synchronize with SystemC time etc.
36  //
37  class tlm_quantumkeeper
38  {
39  public:
40    //
41    // Static setters/getters for the global quantum value.
42    //
43    // The global quantum is the maximum time an initiator can run ahead of
44    // systemC time. All initiators will synchronize on timingpoints that are
45    // multiples of the global quantum value.
46    //
47    static void set_global_quantum(const sc_core::sc_time& t)
48    {
49      tlm::tlm_global_quantum::instance().set(t);
50    }
51
52    static const sc_core::sc_time& get_global_quantum()
53    {
54      return tlm::tlm_global_quantum::instance().get();
55    }
56
57  public:
58    tlm_quantumkeeper() :
59      m_next_sync_point(sc_core::SC_ZERO_TIME),
60      m_local_time(sc_core::SC_ZERO_TIME)
61    {
62    }
63
64    virtual ~tlm_quantumkeeper() {}
65
66    //
67    // Increment the local time (the time the initiator is ahead of the
68    // systemC time) After incrementing the local time an initiator should
69    // check (with the need_sync method) if a sync is required.
70    //
71    virtual void inc(const sc_core::sc_time& t)
72    {
73      m_local_time += t;
74    }
75
76    //
77    // Sets the local time (the time the initiator is ahead of the
78    // systemC time) After changing the local time an initiator should
79    // check (with the need_sync method) if a sync is required.
80    //
81    virtual void set(const sc_core::sc_time& t)
82    {
83      m_local_time = t;
84    }
85
86    //
87    // Checks if a sync to systemC is required for this initiator. This will
88    // be the case if the local time becomes greater than the local (current)
89    // quantum value for this initiator.
90    //
91    virtual bool need_sync() const
92    {
93      return sc_core::sc_time_stamp() + m_local_time >= m_next_sync_point;
94    }
95
96    //
97    // Synchronize to systemC. This call will do a wait for the time the
98    // initiator was running ahead of systemC time and reset the
99    // tlm_quantumkeeper.
100    //
101    virtual void sync()
102    {
103      sc_core::wait(m_local_time);
104      reset();
105    }
106
107    //
108    // Non-virtual convenience method to set the local time and sync only if needed
109    //
110    void set_and_sync(const sc_core::sc_time& t)
111    {
112      set(t);
113      if (need_sync())
114        sync();
115    }
116
117    //
118    // Resets the local time to SC_ZERO_TIME and computes the value of the
119    // next local quantum. This method should be called by an initiator after
120    // a wait because of a synchronization request by a target (TLM_ACCEPTED,
121    // or TLM_UPDATED).
122    //
123    virtual void reset()
124    {
125      m_local_time = sc_core::SC_ZERO_TIME;
126      m_next_sync_point = sc_core::sc_time_stamp() + compute_local_quantum();
127    }
128
129    //
130    // Helper function to get the current systemC time, taken the local time
131    // into account. The current systemC time is calculated as the time
132    // returned by sc_time_stamp incremeneted with the time the initiator is
133    // running ahead.
134    //
135    virtual sc_core::sc_time get_current_time() const
136    {
137      return sc_core::sc_time_stamp() + m_local_time;
138    }
139
140    //
141    // Helper functions to get the time the initiator is running ahead of
142    // systenC (local time). This time should be passed to a target in the
143    // nb_transport call
144    //
145    virtual sc_core::sc_time get_local_time() const
146    {
147      return m_local_time;
148    }
149
150  protected:
151    //
152    // Calculate the next local quantum for this initiator.
153    //
154    // The method can be overloaded in a derived object if an initiator wants
155    // to use another local quantum. This derived object should also take the
156    // global quantum into account. It's local quantum should not be set to a
157    // value that is larger than the quantum returned by the
158    // compute_local_quantum of the tlm_global_quantum singleton.
159    //
160    virtual sc_core::sc_time compute_local_quantum()
161    {
162      return tlm::tlm_global_quantum::instance().compute_local_quantum();
163    }
164
165  protected:
166    sc_core::sc_time m_next_sync_point;
167    sc_core::sc_time m_local_time;
168  };
169
170} // namespace tlm
171
172#endif
173