Changes between Version 78 and Version 79 of Writing Rules/Tlmt
- Timestamp:
- Nov 16, 2008, 2:57:08 PM (15 years ago)
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Writing Rules/Tlmt
v78 v79 26 26 The interested user should also look at the [WritingRules/General general SoCLib rules]. 27 27 28 = B) Single VCI initiator and singleVCI target =28 = B) VCI initiator and VCI target = 29 29 30 30 Figure 1 presents a minimal system containing one single VCI initiator, '''my_initiator''' , and one single … … 82 82 arrays pointers and its associated size in bytes. 83 83 84 Dedicated VCI accessors are used to define the VCI transaction type, that can either be '''set_read()''' (for read command),85 '''set_write()''' (for write command),'''set_locked_read()''' (foratomic locked read),86 and '''set_store_cond()''' (for atomic store conditional). The '''set_src_id()''', '''set_trd_id()''' and '''set_pkt_id()''' functions84 Dedicated VCI accessors are used to define the VCI transaction type, that can either be '''set_read()''' (for VCI read command), 85 '''set_write()''' (for VCI write command),'''set_locked_read()''' (for VCI atomic locked read), 86 and '''set_store_cond()''' (for VCI atomic store conditional). The '''set_src_id()''', '''set_trd_id()''' and '''set_pkt_id()''' functions 87 87 respectively set the VCI source, thread and packet identifiers. 88 88 89 NB : The bytearray approach defined by TLM2.0 can degrade the simulation speed,90 as the existing SoCLib models use uint32_t arrays to model both the embedded memor yand the caches...91 Experiments are currently in progress to evaluate the performance degradation incurred by this byteformatting.92 It is therefore possible that the types of the '''m_data''' and '''m_byte_enable'''of the '''tlmt_vci_transaction'''89 NB : The char array approach defined by TLM2.0 can degrade the simulation speed, 90 as the existing SoCLib models use uint32_t arrays to model both the embedded memories and the caches... 91 Experiments are currently in progress to evaluate the performance degradation incurred by this char <-> uint formatting. 92 It is therefore possible that the types of the data and byte_enable fields of the '''tlmt_vci_transaction''' 93 93 will be changed to '''uint32*''' . 94 94 … … 104 104 and '''getLocalTime()'''. 105 105 {{{ 106 sc_core::sc_time m_local Time; // the initiator local time106 sc_core::sc_time m_local_time; // the initiator local time 107 107 ... 108 108 void addLocalTime(sc_core::sc_time t); // add an increment to the local time … … 111 111 }}} 112 112 113 The boolean member variable '''m_activity ''' indicates if the initiator is currently active.113 The boolean member variable '''m_activity_status''' indicates if the initiator is currently active. 114 114 It is used by the arbitration threads contained in the '''vci_vgmn''' interconnect, as described in section F. 115 115 The corresponding access functions are '''setActivity()''' and '''getActivity()'''. 116 116 {{{ 117 bool m_activity ;117 bool m_activity_status; 118 118 ... 119 119 void setActivity(bool t); // set the activity status (true if the component is active) … … 123 123 The '''execLoop()''' method, describing the initiator behaviour must be declared as a member function. 124 124 125 The '''my_initiator''' class must define a call-back function to handle the VCI response packets. 126 127 Finally, the it must contain a member variable '''p_vci_init''', of type '''tlmt_simple_initiator_socket'''. 128 This member variable represents the VCI initiator port. 125 The '''my_initiator''' class contains a member variable '''p_vci_init''', of type '''tlmt_simple_initiator_socket''', representing the VCI initiator port. 126 127 It must also define an interface function to handle the VCI response packets. 129 128 130 129 == D.2) Sending a VCI command packet == … … 141 140 142 141 The first argument is a pointer to the payload, the second represents the phase, and the third 143 argument contains the initiator local time. 142 argument contains the initiator local time. The return value is not used in this TLM-T implementation. 144 143 145 144 The '''nb_transport_fw()''' function is non-blocking. … … 150 149 == D.3) Receiving a VCI response packet == 151 150 152 To receive a VCI response packet, a call-backfunction must be defined as a member function of the153 class '''my_initiator'''. This call-backfunction (named '''vci_rsp_received()''' in the example), must be linked to151 To receive a VCI response packet, an interface function must be defined as a member function of the 152 class '''my_initiator'''. This function (named '''vci_rsp_received()''' in the example), must be linked to 154 153 the '''p_vci_init''' port, and is executed each time a VCI response packet is received on the '''p_vci_init''' port. 155 154 The function name is not constrained, but the arguments must respect the following prototype: … … 160 159 sc_core::sc_time &time); // response time 161 160 }}} 162 The return value (type tlm::tlm_sync_enum) is not used in this tlmt implementation, and must be sytematically set to tlm::TLM_COMPLETED. 163 164 In the general case, the actions executed by the call-back function depend on the transaction type defined in the payload 165 ('''m_command''', '''m_pktid''' and '''m_trdid''' fields). 166 For sake of simplicity, the call-back function proposed in the example below does not make any distinction between transaction types. 161 The return value (type tlm::tlm_sync_enum) is not used in this TLM-T implementation, and must be sytematically set to tlm::TLM_COMPLETED. 162 163 In the general case, the actions executed by the interface function depend on both the phase argument, and on the transaction type (defined in the payload). 164 For sake of simplicity, the interface function proposed below does not make any distinction between transaction types. 167 165 168 166 == D.4) Initiator Constructor == 169 167 170 168 The constructor of the class '''my_initiator''' must initialize all the member variables, including 171 the '''p_vci_init''' port. The '''vci_rsp_received()''' call-backfunction being executed in the context of the thread sending172 the response packet, a link between the '''p_vci_init''' port and this call-backfunction must be established.169 the '''p_vci_init''' port. The '''vci_rsp_received()''' function being executed in the context of the thread sending 170 the response packet, a link between the '''p_vci_init''' port and this interface function must be established. 173 171 174 172 The constructor for the '''p_vci_init''' port must be called with the following arguments: … … 204 202 = E) VCI target modeling = 205 203 206 In th e proposed example, the '''my_target''' component handles all VCI commands in the same way, and there is no error management.204 In this example, the '''my_target''' component handles all VCI command types in the same way, and there is no error management. 207 205 208 206 == E.1) Member variables & methods == … … 210 208 The class '''my_target''' inherits from the class '''sc_core::sc_module'''. The class '''my_target''' contains a member 211 209 variable '''p_vci_target''' of type '''tlmt_simple_target_socket''', representing the VCI target port. 212 It contains a call-backfunction to handle the received VCI command packets, as described below.210 It contains an interface function to handle the received VCI command packets, as described below. 213 211 214 212 == E.2) Receiving a VCI command packet == 215 213 216 To receive a VCI command packet, a call-backfunction must be defined as a member function of the class '''my_target'''.217 This call-backfunction (named '''vci_cmd_received()''' in the example), is executed each time a VCI command packet is received on214 To receive a VCI command packet, an interface function must be defined as a member function of the class '''my_target'''. 215 This function (named '''vci_cmd_received()''' in the example), is executed each time a VCI command packet is received on 218 216 the '''p_vci_target''' port. The function name is not constrained, but the arguments must respect the following prototype: 219 217 {{{ … … 223 221 sc_core::sc_time &time); // time 224 222 }}} 223 The return value (type tlm::tlm_sync_enum) is not used in this TLM-T implementation, and must be sytematically set to tlm::TLM_COMPLETED. 225 224 226 225 == E.3) Sending a VCI response packet == 227 226 228 To send a VCI response packet the call-back function '''vci_cmd_received()''' use the '''nb_transport_bw()''' method,that is a member function of227 To send a VCI response packet the call-back function '''vci_cmd_received()''' uses the '''nb_transport_bw()''' method, defined by TLM2.0, that is a member function of 229 228 the class '''tlmt_simple_target_socket''', and has the same arguments as the '''nb_transport_fw()''' function. 230 229 Respecting the general TLM2.0 policy, the payload argument refers to the same '''tlmt_vci_transaction''' object for both the '''nb_transport_fw()''' and '''nb_transport_bw()''' functions, 231 and the associated call-back functions. The set_response_status field must be documented for all transaction types, but only two values are used in this TLM-T implementation:230 and the associated interface functions. Only two values are used for the '''response_status''' field in this TLM-T implementation: 232 231 * TLMT_OK_RESPONSE 233 232 * TLMT_ERROR_RESPONSE … … 235 234 236 235 {{{ 236 tlm::tlm_sync_enum vci_cmd_received ( 237 soclib_vci_types::tlm_payload_type &payload, 238 soclib_vci_types::tlm_phase_type &phase 239 sc_core::sc_time &time) 240 { 241 ... 237 242 payload.set_response_status(soclib::tlmt::TLMT_OK_RESPONSE); 238 243 phase = soclib::tlmt::TLMT_RSP; 239 244 time = time + (nwords * UNIT_TIME); 240 245 p_vci_target->nb_transport_bw(payload, phase, time); 246 } 241 247 }}} 242 248 … … 244 250 245 251 The constructor of the class '''my_target''' must initialize all the member variables, including 246 the '''p_vci_target''' port. The '''vci_cmd_received()''' call-backfunction being executed in the context of the thread sending252 the '''p_vci_target''' port. The '''vci_cmd_received()''' function being executed in the context of the thread sending 247 253 the command packet, a link between the '''p_vci_target''' port and the call-back function must be established. 248 254 The '''my_target''' constructor must be called with the following arguments: … … 262 268 }}} 263 269 264 = F) VCI Interconnect model ling =270 = F) VCI Interconnect modeling = 265 271 266 272 The VCI interconnect used for the TLM-T simulation is a generic interconnection network, named '''!VciVgmn'''. 267 273 The two main parameters are the number of initiators, and the number of targets. In TLM-T simulation, 268 we don't want to reproduce the cycle-accuratebehavior of a particular interconnect. We only want to simulate the contention in274 we don't want to reproduce the detailed, cycle-accurate, behavior of a particular interconnect. We only want to simulate the contention in 269 275 the network, when several VCI intitiators try to reach the same VCI target. 270 Therefore, the network is actually modeled as a complete cross-bar : In a physical network such as the multi-stage network described271 in Figure 2.a, conflicts can appear at any intermediate switch. In the '''!VciVgmn''' network described in Figure 2.b, conflicts can272 only happen at the output ports.It is possible to specify a specific latency for each input/output couple. As in most physical273 interconnects, the general arbitration policy is round-robin.276 In a physical network such as the multi-stage network described in Figure 2.a, conflicts can appear at any intermediate switch. 277 The '''!VciVgmn''' network, described in Figure 2.b, is modeled as a cross-bar, and conflicts can only happen at the output ports. 278 It is possible to specify a specific latency for each input/output couple. As in most physical 279 interconnects, the general arbitration policy for each output port is round-robin. 274 280 275 281 [[Image(tlmt_figure_2.png, nolink)]] … … 279 285 There is actually two fully independent networks for VCI command packets and VCI response packets. There is a routing function for each input 280 286 port, and an arbitration function for each output port, but the two networks are not symmetrical : 281 * For the command network, the arbitration policy is distributed: there is one arbitration thread for each output port 282 (i.e. one arbitration thread for each VCI target). Each arbitration thread is modeled by a SC_THREAD, and contains a local clock.287 * For the command network, the arbitration policy is distributed: there is one arbitration thread for each output port (i.e. one arbitration thread for each VCI target). Each arbitration thread is modeled by a SC_THREAD, and contains a local time. This time represents the target local time. 288 283 289 * For the response network, there are no conflicts, and there is no need for arbitration. Therefore, there is no thread 284 290 (and no local time) and the response network is implemented by simple function calls.
