src/mem/xbar.hh

   1 /*
   2  * Copyright (c) 2011-2015, 2018-2019 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 #include <unordered_map>
  56
  57 #include "base/addr_range_map.hh"
  58 #include "base/types.hh"
  59 #include "mem/qport.hh"
  60 #include "params/BaseXBar.hh"
  61 #include "sim/clocked_object.hh"
  62 #include "sim/stats.hh"
  63
  64 /**
  65  * The base crossbar contains the common elements of the non-coherent
  66  * and coherent crossbar. It is an abstract class that does not have
  67  * any of the functionality relating to the actual reception and
  68  * transmission of packets, as this is left for the subclasses.
  69  *
  70  * The BaseXBar is responsible for the basic flow control (busy or
  71  * not), the administration of retries, and the address decoding.
  72  */
  73 class BaseXBar : public ClockedObject
  74 {
  75
  76   protected:
  77
  78     /**
  79      * A layer is an internal crossbar arbitration point with its own
  80      * flow control. Each layer is a converging multiplexer tree. By
  81      * instantiating one layer per destination port (and per packet
  82      * type, i.e. request, response, snoop request and snoop
  83      * response), we model full crossbar structures like AXI, ACE,
  84      * PCIe, etc.
  85      *
  86      * The template parameter, PortClass, indicates the destination
  87      * port type for the layer. The retry list holds either master
  88      * ports or slave ports, depending on the direction of the
  89      * layer. Thus, a request layer has a retry list containing slave
  90      * ports, whereas a response layer holds master ports.
  91      */
  92     template <typename SrcType, typename DstType>
  93     class Layer : public Drainable, public Stats::Group
  94     {
  95
  96       public:
  97
  98         /**
  99          * Create a layer and give it a name. The layer uses
 100          * the crossbar an event manager.
 101          *
 102          * @param _port destination port the layer converges at
 103          * @param _xbar the crossbar this layer belongs to
 104          * @param _name the layer's name
 105          */
 106         Layer(DstType& _port, BaseXBar& _xbar, const std::string& _name);
 107
 108         /**
 109          * Drain according to the normal semantics, so that the crossbar
 110          * can tell the layer to drain, and pass an event to signal
 111          * back when drained.
 112          *
 113          * @param de drain event to call once drained
 114          *
 115          * @return 1 if busy or waiting to retry, or 0 if idle
 116          */
 117         DrainState drain() override;
 118
 119         const std::string name() const { return _name; }
 120
 121
 122         /**
 123          * Determine if the layer accepts a packet from a specific
 124          * port. If not, the port in question is also added to the
 125          * retry list. In either case the state of the layer is
 126          * updated accordingly.
 127          *
 128          * @param port Source port presenting the packet
 129          *
 130          * @return True if the layer accepts the packet
 131          */
 132         bool tryTiming(SrcType* src_port);
 133
 134         /**
 135          * Deal with a destination port accepting a packet by potentially
 136          * removing the source port from the retry list (if retrying) and
 137          * occupying the layer accordingly.
 138          *
 139          * @param busy_time Time to spend as a result of a successful send
 140          */
 141         void succeededTiming(Tick busy_time);
 142
 143         /**
 144          * Deal with a destination port not accepting a packet by
 145          * potentially adding the source port to the retry list (if
 146          * not already at the front) and occupying the layer
 147          * accordingly.
 148          *
 149          * @param src_port Source port
 150          * @param busy_time Time to spend as a result of a failed send
 151          */
 152         void failedTiming(SrcType* src_port, Tick busy_time);
 153
 154         void occupyLayer(Tick until);
 155
 156         /**
 157          * Send a retry to the port at the head of waitingForLayer. The
 158          * caller must ensure that the list is not empty.
 159          */
 160         void retryWaiting();
 161
 162         /**
 163          * Handle a retry from a neighbouring module. This wraps
 164          * retryWaiting by verifying that there are ports waiting
 165          * before calling retryWaiting.
 166          */
 167         void recvRetry();
 168
 169       protected:
 170
 171         /**
 172          * Sending the actual retry, in a manner specific to the
 173          * individual layers. Note that for a MasterPort, there is
 174          * both a RequestLayer and a SnoopResponseLayer using the same
 175          * port, but using different functions for the flow control.
 176          */
 177         virtual void sendRetry(SrcType* retry_port) = 0;
 178
 179       private:
 180
 181         /** The destination port this layer converges at. */
 182         DstType& port;
 183
 184         /** The crossbar this layer is a part of. */
 185         BaseXBar& xbar;
 186
 187         std::string _name;
 188
 189         /**
 190          * We declare an enum to track the state of the layer. The
 191          * starting point is an idle state where the layer is waiting
 192          * for a packet to arrive. Upon arrival, the layer
 193          * transitions to the busy state, where it remains either
 194          * until the packet transfer is done, or the header time is
 195          * spent. Once the layer leaves the busy state, it can
 196          * either go back to idle, if no packets have arrived while it
 197          * was busy, or the layer goes on to retry the first port
 198          * in waitingForLayer. A similar transition takes place from
 199          * idle to retry if the layer receives a retry from one of
 200          * its connected ports. The retry state lasts until the port
 201          * in questions calls sendTiming and returns control to the
 202          * layer, or goes to a busy state if the port does not
 203          * immediately react to the retry by calling sendTiming.
 204          */
 205         enum State { IDLE, BUSY, RETRY };
 206
 207         State state;
 208
 209         /**
 210          * A deque of ports that retry should be called on because
 211          * the original send was delayed due to a busy layer.
 212          */
 213         std::deque<SrcType*> waitingForLayer;
 214
 215         /**
 216          * Track who is waiting for the retry when receiving it from a
 217          * peer. If no port is waiting NULL is stored.
 218          */
 219         SrcType* waitingForPeer;
 220
 221         /**
 222          * Release the layer after being occupied and return to an
 223          * idle state where we proceed to send a retry to any
 224          * potential waiting port, or drain if asked to do so.
 225          */
 226         void releaseLayer();
 227         EventFunctionWrapper releaseEvent;
 228
 229         /**
 230          * Stats for occupancy and utilization. These stats capture
 231          * the time the layer spends in the busy state and are thus only
 232          * relevant when the memory system is in timing mode.
 233          */
 234         Stats::Scalar occupancy;
 235         Stats::Formula utilization;
 236
 237     };
 238
 239     class ReqLayer : public Layer<SlavePort, MasterPort>
 240     {
 241       public:
 242         /**
 243          * Create a request layer and give it a name.
 244          *
 245          * @param _port destination port the layer converges at
 246          * @param _xbar the crossbar this layer belongs to
 247          * @param _name the layer's name
 248          */
 249         ReqLayer(MasterPort& _port, BaseXBar& _xbar, const std::string& _name) :
 250             Layer(_port, _xbar, _name)
 251         {}
 252
 253       protected:
 254         void
 255         sendRetry(SlavePort* retry_port) override
 256         {
 257             retry_port->sendRetryReq();
 258         }
 259     };
 260
 261     class RespLayer : public Layer<MasterPort, SlavePort>
 262     {
 263       public:
 264         /**
 265          * Create a response layer and give it a name.
 266          *
 267          * @param _port destination port the layer converges at
 268          * @param _xbar the crossbar this layer belongs to
 269          * @param _name the layer's name
 270          */
 271         RespLayer(SlavePort& _port, BaseXBar& _xbar,
 272                   const std::string& _name) :
 273             Layer(_port, _xbar, _name)
 274         {}
 275
 276       protected:
 277         void
 278         sendRetry(MasterPort* retry_port) override
 279         {
 280             retry_port->sendRetryResp();
 281         }
 282     };
 283
 284     class SnoopRespLayer : public Layer<SlavePort, MasterPort>
 285     {
 286       public:
 287         /**
 288          * Create a snoop response layer and give it a name.
 289          *
 290          * @param _port destination port the layer converges at
 291          * @param _xbar the crossbar this layer belongs to
 292          * @param _name the layer's name
 293          */
 294         SnoopRespLayer(MasterPort& _port, BaseXBar& _xbar,
 295                        const std::string& _name) :
 296             Layer(_port, _xbar, _name)
 297         {}
 298
 299       protected:
 300
 301         void
 302         sendRetry(SlavePort* retry_port) override
 303         {
 304             retry_port->sendRetrySnoopResp();
 305         }
 306     };
 307
 308     /**
 309      * Cycles of front-end pipeline including the delay to accept the request
 310      * and to decode the address.
 311      */
 312     const Cycles frontendLatency;
 313     const Cycles forwardLatency;
 314     const Cycles responseLatency;
 315     /** the width of the xbar in bytes */
 316     const uint32_t width;
 317
 318     AddrRangeMap<PortID, 3> portMap;
 319
 320     /**
 321      * Remember where request packets came from so that we can route
 322      * responses to the appropriate port. This relies on the fact that
 323      * the underlying Request pointer inside the Packet stays
 324      * constant.
 325      */
 326     std::unordered_map<RequestPtr, PortID> routeTo;
 327
 328     /** all contigous ranges seen by this crossbar */
 329     AddrRangeList xbarRanges;
 330
 331     AddrRange defaultRange;
 332
 333     /**
 334      * Function called by the port when the crossbar is recieving a
 335      * range change.
 336      *
 337      * @param master_port_id id of the port that received the change
 338      */
 339     virtual void recvRangeChange(PortID master_port_id);
 340
 341     /**
 342      * Find which port connected to this crossbar (if any) should be
 343      * given a packet with this address range.
 344      *
 345      * @param addr_range Address range to find port for.
 346      * @return id of port that the packet should be sent out of.
 347      */
 348     PortID findPort(AddrRange addr_range);
 349
 350     /**
 351      * Return the address ranges the crossbar is responsible for.
 352      *
 353      * @return a list of non-overlapping address ranges
 354      */
 355     AddrRangeList getAddrRanges() const;
 356
 357     /**
 358      * Calculate the timing parameters for the packet. Updates the
 359      * headerDelay and payloadDelay fields of the packet
 360      * object with the relative number of ticks required to transmit
 361      * the header and the payload, respectively.
 362      *
 363      * @param pkt Packet to populate with timings
 364      * @param header_delay Header delay to be added
 365      */
 366     void calcPacketTiming(PacketPtr pkt, Tick header_delay);
 367
 368     /**
 369      * Remember for each of the master ports of the crossbar if we got
 370      * an address range from the connected slave. For convenience,
 371      * also keep track of if we got ranges from all the slave modules
 372      * or not.
 373      */
 374     std::vector<bool> gotAddrRanges;
 375     bool gotAllAddrRanges;
 376
 377     /** The master and slave ports of the crossbar */
 378     std::vector<QueuedSlavePort*> slavePorts;
 379     std::vector<MasterPort*> masterPorts;
 380
 381     /** Port that handles requests that don't match any of the interfaces.*/
 382     PortID defaultPortID;
 383
 384     /** If true, use address range provided by default device.  Any
 385        address not handled by another port and not in default device's
 386        range will cause a fatal error.  If false, just send all
 387        addresses not handled by another port to default device. */
 388     const bool useDefaultRange;
 389
 390     BaseXBar(const BaseXBarParams *p);
 391
 392     /**
 393      * Stats for transaction distribution and data passing through the
 394      * crossbar. The transaction distribution is globally counting
 395      * different types of commands. The packet count and total packet
 396      * size are two-dimensional vectors that are indexed by the
 397      * slave port and master port id (thus the neighbouring master and
 398      * neighbouring slave), summing up both directions (request and
 399      * response).
 400      */
 401     Stats::Vector transDist;
 402     Stats::Vector2d pktCount;
 403     Stats::Vector2d pktSize;
 404
 405   public:
 406
 407     virtual ~BaseXBar();
 408
 409     /** A function used to return the port associated with this object. */
 410     Port &getPort(const std::string &if_name,
 411                   PortID idx=InvalidPortID) override;
 412
 413     void regStats() override;
 414 };
 415
 416 #endif //__MEM_XBAR_HH__