1/* 2 * Copyright (c) 2011-2015 ARM Limited 3 * All rights reserved 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Copyright (c) 2002-2005 The Regents of The University of Michigan 15 * All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions are 19 * met: redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer; 21 * redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution; 24 * neither the name of the copyright holders nor the names of its 25 * contributors may be used to endorse or promote products derived from 26 * this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 39 * 40 * Authors: Ron Dreslinski 41 * Ali Saidi 42 * Andreas Hansson 43 * William Wang 44 */ 45 46/** 47 * @file 48 * Declaration of an abstract crossbar base class. 49 */ 50 51#ifndef __MEM_XBAR_HH__ 52#define __MEM_XBAR_HH__ 53 54#include <deque> 55 56#include "base/addr_range_map.hh" 57#include "base/hashmap.hh" 58#include "base/types.hh" 59#include "mem/mem_object.hh" 60#include "params/BaseXBar.hh" 61#include "sim/stats.hh" 62 63/** 64 * The base crossbar contains the common elements of the non-coherent 65 * and coherent crossbar. It is an abstract class that does not have 66 * any of the functionality relating to the actual reception and 67 * transmission of packets, as this is left for the subclasses. 68 * 69 * The BaseXBar is responsible for the basic flow control (busy or 70 * not), the administration of retries, and the address decoding. 71 */ 72class BaseXBar : public MemObject 73{ 74 75 protected: 76 77 /** 78 * A layer is an internal crossbar arbitration point with its own 79 * flow control. Each layer is a converging multiplexer tree. By 80 * instantiating one layer per destination port (and per packet 81 * type, i.e. request, response, snoop request and snoop 82 * response), we model full crossbar structures like AXI, ACE, 83 * PCIe, etc. 84 * 85 * The template parameter, PortClass, indicates the destination 86 * port type for the layer. The retry list holds either master 87 * ports or slave ports, depending on the direction of the 88 * layer. Thus, a request layer has a retry list containing slave 89 * ports, whereas a response layer holds master ports. 90 */ 91 template <typename SrcType, typename DstType> 92 class Layer : public Drainable 93 { 94 95 public: 96 97 /** 98 * Create a layer and give it a name. The layer uses 99 * the crossbar an event manager. 100 * 101 * @param _port destination port the layer converges at 102 * @param _xbar the crossbar this layer belongs to 103 * @param _name the layer's name 104 */ 105 Layer(DstType& _port, BaseXBar& _xbar, const std::string& _name); 106 107 /** 108 * Drain according to the normal semantics, so that the crossbar 109 * can tell the layer to drain, and pass an event to signal 110 * back when drained. 111 * 112 * @param de drain event to call once drained 113 * 114 * @return 1 if busy or waiting to retry, or 0 if idle 115 */ 116 unsigned int drain(DrainManager *dm); 117 118 /** 119 * Get the crossbar layer's name 120 */ 121 const std::string name() const { return xbar.name() + _name; } 122 123 124 /** 125 * Determine if the layer accepts a packet from a specific 126 * port. If not, the port in question is also added to the 127 * retry list. In either case the state of the layer is 128 * updated accordingly. 129 * 130 * @param port Source port presenting the packet 131 * 132 * @return True if the layer accepts the packet 133 */ 134 bool tryTiming(SrcType* src_port); 135 136 /** 137 * Deal with a destination port accepting a packet by potentially 138 * removing the source port from the retry list (if retrying) and 139 * occupying the layer accordingly. 140 * 141 * @param busy_time Time to spend as a result of a successful send 142 */ 143 void succeededTiming(Tick busy_time); 144 145 /** 146 * Deal with a destination port not accepting a packet by 147 * potentially adding the source port to the retry list (if 148 * not already at the front) and occupying the layer 149 * accordingly. 150 * 151 * @param src_port Source port 152 * @param busy_time Time to spend as a result of a failed send 153 */ 154 void failedTiming(SrcType* src_port, Tick busy_time); 155 156 /** Occupy the layer until until */ 157 void occupyLayer(Tick until); 158 159 /** 160 * Send a retry to the port at the head of waitingForLayer. The 161 * caller must ensure that the list is not empty. 162 */ 163 void retryWaiting(); 164 165 /** 166 * Handle a retry from a neighbouring module. This wraps 167 * retryWaiting by verifying that there are ports waiting 168 * before calling retryWaiting. 169 */ 170 void recvRetry(); 171 172 /** 173 * Register stats for the layer 174 */ 175 void regStats(); 176 177 protected: 178 179 /** 180 * Sending the actual retry, in a manner specific to the 181 * individual layers. Note that for a MasterPort, there is 182 * both a RequestLayer and a SnoopResponseLayer using the same 183 * port, but using different functions for the flow control. 184 */ 185 virtual void sendRetry(SrcType* retry_port) = 0; 186 187 private: 188 189 /** The destination port this layer converges at. */ 190 DstType& port; 191 192 /** The crossbar this layer is a part of. */ 193 BaseXBar& xbar; 194 195 /** A name for this layer. */ 196 std::string _name; 197 198 /** 199 * We declare an enum to track the state of the layer. The 200 * starting point is an idle state where the layer is waiting 201 * for a packet to arrive. Upon arrival, the layer 202 * transitions to the busy state, where it remains either 203 * until the packet transfer is done, or the header time is 204 * spent. Once the layer leaves the busy state, it can 205 * either go back to idle, if no packets have arrived while it 206 * was busy, or the layer goes on to retry the first port 207 * in waitingForLayer. A similar transition takes place from 208 * idle to retry if the layer receives a retry from one of 209 * its connected ports. The retry state lasts until the port 210 * in questions calls sendTiming and returns control to the 211 * layer, or goes to a busy state if the port does not 212 * immediately react to the retry by calling sendTiming. 213 */ 214 enum State { IDLE, BUSY, RETRY }; 215 216 /** track the state of the layer */ 217 State state; 218 219 /** manager to signal when drained */ 220 DrainManager *drainManager; 221 222 /** 223 * A deque of ports that retry should be called on because 224 * the original send was delayed due to a busy layer. 225 */ 226 std::deque<SrcType*> waitingForLayer; 227 228 /** 229 * Track who is waiting for the retry when receiving it from a 230 * peer. If no port is waiting NULL is stored. 231 */ 232 SrcType* waitingForPeer; 233 234 /** 235 * Release the layer after being occupied and return to an 236 * idle state where we proceed to send a retry to any 237 * potential waiting port, or drain if asked to do so. 238 */ 239 void releaseLayer(); 240 241 /** event used to schedule a release of the layer */ 242 EventWrapper<Layer, &Layer::releaseLayer> releaseEvent; 243 244 /** 245 * Stats for occupancy and utilization. These stats capture 246 * the time the layer spends in the busy state and are thus only 247 * relevant when the memory system is in timing mode. 248 */ 249 Stats::Scalar occupancy; 250 Stats::Formula utilization; 251 252 }; 253 254 class ReqLayer : public Layer<SlavePort,MasterPort> 255 { 256 public: 257 /** 258 * Create a request layer and give it a name. 259 * 260 * @param _port destination port the layer converges at 261 * @param _xbar the crossbar this layer belongs to 262 * @param _name the layer's name 263 */ 264 ReqLayer(MasterPort& _port, BaseXBar& _xbar, const std::string& _name) : 265 Layer(_port, _xbar, _name) {} 266 267 protected: 268 269 void sendRetry(SlavePort* retry_port) 270 { retry_port->sendRetryReq(); } 271 }; 272 273 class RespLayer : public Layer<MasterPort,SlavePort> 274 { 275 public: 276 /** 277 * Create a response layer and give it a name. 278 * 279 * @param _port destination port the layer converges at 280 * @param _xbar the crossbar this layer belongs to 281 * @param _name the layer's name 282 */ 283 RespLayer(SlavePort& _port, BaseXBar& _xbar, const std::string& _name) : 284 Layer(_port, _xbar, _name) {} 285 286 protected: 287 288 void sendRetry(MasterPort* retry_port) 289 { retry_port->sendRetryResp(); } 290 }; 291 292 class SnoopRespLayer : public Layer<SlavePort,MasterPort> 293 { 294 public: 295 /** 296 * Create a snoop response layer and give it a name. 297 * 298 * @param _port destination port the layer converges at 299 * @param _xbar the crossbar this layer belongs to 300 * @param _name the layer's name 301 */ 302 SnoopRespLayer(MasterPort& _port, BaseXBar& _xbar, 303 const std::string& _name) : 304 Layer(_port, _xbar, _name) {} 305 306 protected: 307 308 void sendRetry(SlavePort* retry_port) 309 { retry_port->sendRetrySnoopResp(); } 310 }; 311
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