src/mem/xbar.hh

   1 /*
   2  * Copyright (c) 2011-2015, 2018-2020 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
  41 /**
  42  * @file
  43  * Declaration of an abstract crossbar base class.
  44  */
  45
  46 #ifndef __MEM_XBAR_HH__
  47 #define __MEM_XBAR_HH__
  48
  49 #include <deque>
  50 #include <unordered_map>
  51
  52 #include "base/addr_range_map.hh"
  53 #include "base/types.hh"
  54 #include "mem/qport.hh"
  55 #include "params/BaseXBar.hh"
  56 #include "sim/clocked_object.hh"
  57 #include "sim/stats.hh"
  58
  59 /**
  60  * The base crossbar contains the common elements of the non-coherent
  61  * and coherent crossbar. It is an abstract class that does not have
  62  * any of the functionality relating to the actual reception and
  63  * transmission of packets, as this is left for the subclasses.
  64  *
  65  * The BaseXBar is responsible for the basic flow control (busy or
  66  * not), the administration of retries, and the address decoding.
  67  */
  68 class BaseXBar : public ClockedObject
  69 {
  70
  71   protected:
  72
  73     /**
  74      * A layer is an internal crossbar arbitration point with its own
  75      * flow control. Each layer is a converging multiplexer tree. By
  76      * instantiating one layer per destination port (and per packet
  77      * type, i.e. request, response, snoop request and snoop
  78      * response), we model full crossbar structures like AXI, ACE,
  79      * PCIe, etc.
  80      *
  81      * The template parameter, PortClass, indicates the destination
  82      * port type for the layer. The retry list holds either memory-side ports
  83      * or CPU-side ports, depending on the direction of the
  84      * layer. Thus, a request layer has a retry list containing
  85      * CPU-side ports, whereas a response layer holds memory-side ports.
  86      */
  87     template <typename SrcType, typename DstType>
  88     class Layer : public Drainable, public Stats::Group
  89     {
  90
  91       public:
  92
  93         /**
  94          * Create a layer and give it a name. The layer uses
  95          * the crossbar an event manager.
  96          *
  97          * @param _port destination port the layer converges at
  98          * @param _xbar the crossbar this layer belongs to
  99          * @param _name the layer's name
 100          */
 101         Layer(DstType& _port, BaseXBar& _xbar, const std::string& _name);
 102
 103         /**
 104          * Drain according to the normal semantics, so that the crossbar
 105          * can tell the layer to drain, and pass an event to signal
 106          * back when drained.
 107          *
 108          * @param de drain event to call once drained
 109          *
 110          * @return 1 if busy or waiting to retry, or 0 if idle
 111          */
 112         DrainState drain() override;
 113
 114         const std::string name() const { return _name; }
 115
 116
 117         /**
 118          * Determine if the layer accepts a packet from a specific
 119          * port. If not, the port in question is also added to the
 120          * retry list. In either case the state of the layer is
 121          * updated accordingly.
 122          *
 123          * @param port Source port presenting the packet
 124          *
 125          * @return True if the layer accepts the packet
 126          */
 127         bool tryTiming(SrcType* src_port);
 128
 129         /**
 130          * Deal with a destination port accepting a packet by potentially
 131          * removing the source port from the retry list (if retrying) and
 132          * occupying the layer accordingly.
 133          *
 134          * @param busy_time Time to spend as a result of a successful send
 135          */
 136         void succeededTiming(Tick busy_time);
 137
 138         /**
 139          * Deal with a destination port not accepting a packet by
 140          * potentially adding the source port to the retry list (if
 141          * not already at the front) and occupying the layer
 142          * accordingly.
 143          *
 144          * @param src_port Source port
 145          * @param busy_time Time to spend as a result of a failed send
 146          */
 147         void failedTiming(SrcType* src_port, Tick busy_time);
 148
 149         void occupyLayer(Tick until);
 150
 151         /**
 152          * Send a retry to the port at the head of waitingForLayer. The
 153          * caller must ensure that the list is not empty.
 154          */
 155         void retryWaiting();
 156
 157         /**
 158          * Handle a retry from a neighbouring module. This wraps
 159          * retryWaiting by verifying that there are ports waiting
 160          * before calling retryWaiting.
 161          */
 162         void recvRetry();
 163
 164       protected:
 165
 166         /**
 167          * Sending the actual retry, in a manner specific to the
 168          * individual layers. Note that for a RequestPort, there is
 169          * both a RequestLayer and a SnoopResponseLayer using the same
 170          * port, but using different functions for the flow control.
 171          */
 172         virtual void sendRetry(SrcType* retry_port) = 0;
 173
 174       private:
 175
 176         /** The destination port this layer converges at. */
 177         DstType& port;
 178
 179         /** The crossbar this layer is a part of. */
 180         BaseXBar& xbar;
 181
 182         std::string _name;
 183
 184         /**
 185          * We declare an enum to track the state of the layer. The
 186          * starting point is an idle state where the layer is waiting
 187          * for a packet to arrive. Upon arrival, the layer
 188          * transitions to the busy state, where it remains either
 189          * until the packet transfer is done, or the header time is
 190          * spent. Once the layer leaves the busy state, it can
 191          * either go back to idle, if no packets have arrived while it
 192          * was busy, or the layer goes on to retry the first port
 193          * in waitingForLayer. A similar transition takes place from
 194          * idle to retry if the layer receives a retry from one of
 195          * its connected ports. The retry state lasts until the port
 196          * in questions calls sendTiming and returns control to the
 197          * layer, or goes to a busy state if the port does not
 198          * immediately react to the retry by calling sendTiming.
 199          */
 200         enum State { IDLE, BUSY, RETRY };
 201
 202         State state;
 203
 204         /**
 205          * A deque of ports that retry should be called on because
 206          * the original send was delayed due to a busy layer.
 207          */
 208         std::deque<SrcType*> waitingForLayer;
 209
 210         /**
 211          * Track who is waiting for the retry when receiving it from a
 212          * peer. If no port is waiting NULL is stored.
 213          */
 214         SrcType* waitingForPeer;
 215
 216         /**
 217          * Release the layer after being occupied and return to an
 218          * idle state where we proceed to send a retry to any
 219          * potential waiting port, or drain if asked to do so.
 220          */
 221         void releaseLayer();
 222         EventFunctionWrapper releaseEvent;
 223
 224         /**
 225          * Stats for occupancy and utilization. These stats capture
 226          * the time the layer spends in the busy state and are thus only
 227          * relevant when the memory system is in timing mode.
 228          */
 229         Stats::Scalar occupancy;
 230         Stats::Formula utilization;
 231
 232     };
 233
 234     class ReqLayer : public Layer<ResponsePort, RequestPort>
 235     {
 236       public:
 237         /**
 238          * Create a request layer and give it a name.
 239          *
 240          * @param _port destination port the layer converges at
 241          * @param _xbar the crossbar this layer belongs to
 242          * @param _name the layer's name
 243          */
 244         ReqLayer(RequestPort& _port, BaseXBar& _xbar,
 245         const std::string& _name) :
 246             Layer(_port, _xbar, _name)
 247         {}
 248
 249       protected:
 250         void
 251         sendRetry(ResponsePort* retry_port) override
 252         {
 253             retry_port->sendRetryReq();
 254         }
 255     };
 256
 257     class RespLayer : public Layer<RequestPort, ResponsePort>
 258     {
 259       public:
 260         /**
 261          * Create a response layer and give it a name.
 262          *
 263          * @param _port destination port the layer converges at
 264          * @param _xbar the crossbar this layer belongs to
 265          * @param _name the layer's name
 266          */
 267         RespLayer(ResponsePort& _port, BaseXBar& _xbar,
 268                   const std::string& _name) :
 269             Layer(_port, _xbar, _name)
 270         {}
 271
 272       protected:
 273         void
 274         sendRetry(RequestPort* retry_port) override
 275         {
 276             retry_port->sendRetryResp();
 277         }
 278     };
 279
 280     class SnoopRespLayer : public Layer<ResponsePort, RequestPort>
 281     {
 282       public:
 283         /**
 284          * Create a snoop response layer and give it a name.
 285          *
 286          * @param _port destination port the layer converges at
 287          * @param _xbar the crossbar this layer belongs to
 288          * @param _name the layer's name
 289          */
 290         SnoopRespLayer(RequestPort& _port, BaseXBar& _xbar,
 291                        const std::string& _name) :
 292             Layer(_port, _xbar, _name)
 293         {}
 294
 295       protected:
 296
 297         void
 298         sendRetry(ResponsePort* retry_port) override
 299         {
 300             retry_port->sendRetrySnoopResp();
 301         }
 302     };
 303
 304     /**
 305      * Cycles of front-end pipeline including the delay to accept the request
 306      * and to decode the address.
 307      */
 308     const Cycles frontendLatency;
 309     const Cycles forwardLatency;
 310     const Cycles responseLatency;
 311     /** Cycles the layer is occupied processing the packet header */
 312     const Cycles headerLatency;
 313     /** the width of the xbar in bytes */
 314     const uint32_t width;
 315
 316     AddrRangeMap<PortID, 3> portMap;
 317
 318     /**
 319      * Remember where request packets came from so that we can route
 320      * responses to the appropriate port. This relies on the fact that
 321      * the underlying Request pointer inside the Packet stays
 322      * constant.
 323      */
 324     std::unordered_map<RequestPtr, PortID> routeTo;
 325
 326     /** all contigous ranges seen by this crossbar */
 327     AddrRangeList xbarRanges;
 328
 329     AddrRange defaultRange;
 330
 331     /**
 332      * Function called by the port when the crossbar is recieving a
 333      * range change.
 334      *
 335      * @param mem_side_port_id id of the port that received the change
 336      */
 337     virtual void recvRangeChange(PortID mem_side_port_id);
 338
 339     /**
 340      * Find which port connected to this crossbar (if any) should be
 341      * given a packet with this address range.
 342      *
 343      * @param addr_range Address range to find port for.
 344      * @return id of port that the packet should be sent out of.
 345      */
 346     PortID findPort(AddrRange addr_range);
 347
 348     /**
 349      * Return the address ranges the crossbar is responsible for.
 350      *
 351      * @return a list of non-overlapping address ranges
 352      */
 353     AddrRangeList getAddrRanges() const;
 354
 355     /**
 356      * Calculate the timing parameters for the packet. Updates the
 357      * headerDelay and payloadDelay fields of the packet
 358      * object with the relative number of ticks required to transmit
 359      * the header and the payload, respectively.
 360      *
 361      * @param pkt Packet to populate with timings
 362      * @param header_delay Header delay to be added
 363      */
 364     void calcPacketTiming(PacketPtr pkt, Tick header_delay);
 365
 366     /**
 367      * Remember for each of the memory-side ports of the crossbar if we got
 368      * an address range from the connected CPU-side ports. For convenience,
 369      * also keep track of if we got ranges from all the CPU-side-port modules
 370      * or not.
 371      */
 372     std::vector<bool> gotAddrRanges;
 373     bool gotAllAddrRanges;
 374
 375     /** The memory-side ports and CPU-side ports of the crossbar */
 376     std::vector<QueuedResponsePort*> cpuSidePorts;
 377     std::vector<RequestPort*> memSidePorts;
 378
 379     /** Port that handles requests that don't match any of the interfaces.*/
 380     PortID defaultPortID;
 381
 382     /** If true, use address range provided by default device.  Any
 383        address not handled by another port and not in default device's
 384        range will cause a fatal error.  If false, just send all
 385        addresses not handled by another port to default device. */
 386     const bool useDefaultRange;
 387
 388     BaseXBar(const BaseXBarParams &p);
 389
 390     /**
 391      * Stats for transaction distribution and data passing through the
 392      * crossbar. The transaction distribution is globally counting
 393      * different types of commands. The packet count and total packet
 394      * size are two-dimensional vectors that are indexed by the
 395      * CPU-side port and memory-side port id (thus the neighbouring memory-side
 396      * ports and neighbouring CPU-side ports), summing up both directions
 397      * (request and response).
 398      */
 399     Stats::Vector transDist;
 400     Stats::Vector2d pktCount;
 401     Stats::Vector2d pktSize;
 402
 403   public:
 404
 405     virtual ~BaseXBar();
 406
 407     /** A function used to return the port associated with this object. */
 408     Port &getPort(const std::string &if_name,
 409                   PortID idx=InvalidPortID) override;
 410
 411     void regStats() override;
 412 };
 413
 414 #endif //__MEM_XBAR_HH__