src/mem/serial_link.hh

   1 /*
   2  * Copyright (c) 2011-2013 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) 2006 The Regents of The University of Michigan
  15  * Copyright (c) 2015 The University of Bologna
  16  * All rights reserved.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions are
  20  * met: redistributions of source code must retain the above copyright
  21  * notice, this list of conditions and the following disclaimer;
  22  * redistributions in binary form must reproduce the above copyright
  23  * notice, this list of conditions and the following disclaimer in the
  24  * documentation and/or other materials provided with the distribution;
  25  * neither the name of the copyright holders nor the names of its
  26  * contributors may be used to endorse or promote products derived from
  27  * this software without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  30  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  31  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  32  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  33  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  34  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  35  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  36  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  37  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  38  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  39  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  40  */
  41
  42 /**
  43  * @file
  44  * Declaration of the SerialLink Class, modeling Hybrid-Memory-Cube's serial
  45  * interface.
  46  */
  47
  48 #ifndef __MEM_SERIAL_LINK_HH__
  49 #define __MEM_SERIAL_LINK_HH__
  50
  51 #include <deque>
  52
  53 #include "base/types.hh"
  54 #include "mem/port.hh"
  55 #include "params/SerialLink.hh"
  56 #include "sim/clocked_object.hh"
  57
  58 /**
  59  * SerialLink is a simple variation of the Bridge class, with the ability to
  60  * account for the latency of packet serialization. We assume that the
  61  * serializer component at the transmitter side does not need to receive the
  62  * whole packet to start the serialization. But the deserializer waits for the
  63  * complete packet to check its integrity first.
  64   */
  65 class SerialLink : public ClockedObject
  66 {
  67   protected:
  68
  69     /**
  70      * A deferred packet stores a packet along with its scheduled
  71      * transmission time
  72      */
  73     class DeferredPacket
  74     {
  75
  76       public:
  77
  78         const Tick tick;
  79         const PacketPtr pkt;
  80
  81         DeferredPacket(PacketPtr _pkt, Tick _tick) : tick(_tick), pkt(_pkt)
  82         { }
  83     };
  84
  85     // Forward declaration to allow the CPU-side port to have a pointer
  86     class SerialLinkRequestPort;
  87
  88     /**
  89      * The port on the side that receives requests and sends
  90      * responses. The CPU-side port has a set of address ranges that it
  91      * is responsible for. The CPU-side port also has a buffer for the
  92      * responses not yet sent.
  93      */
  94     class SerialLinkResponsePort : public ResponsePort
  95     {
  96
  97       private:
  98
  99         /** The serial_link to which this port belongs. */
 100         SerialLink& serial_link;
 101
 102         /**
 103          * Request port on the other side of the serial_link.
 104          */
 105         SerialLinkRequestPort& mem_side_port;
 106
 107         /** Minimum request delay though this serial_link. */
 108         const Cycles delay;
 109
 110         /** Address ranges to pass through the serial_link */
 111         const AddrRangeList ranges;
 112
 113         /**
 114          * Response packet queue. Response packets are held in this
 115          * queue for a specified delay to model the processing delay
 116          * of the serial_link. We use a deque as we need to iterate over
 117          * the items for functional accesses.
 118          */
 119         std::deque<DeferredPacket> transmitList;
 120
 121         /** Counter to track the outstanding responses. */
 122         unsigned int outstandingResponses;
 123
 124         /** If we should send a retry when space becomes available. */
 125         bool retryReq;
 126
 127         /** Max queue size for reserved responses. */
 128         unsigned int respQueueLimit;
 129
 130         /**
 131          * Is this side blocked from accepting new response packets.
 132          *
 133          * @return true if the reserved space has reached the set limit
 134          */
 135         bool respQueueFull() const;
 136
 137         /**
 138          * Handle send event, scheduled when the packet at the head of
 139          * the response queue is ready to transmit (for timing
 140          * accesses only).
 141          */
 142         void trySendTiming();
 143
 144         /** Send event for the response queue. */
 145         EventFunctionWrapper sendEvent;
 146
 147       public:
 148
 149         /**
 150          * Constructor for the SerialLinkResponsePort.
 151          *
 152          * @param _name the port name including the owner
 153          * @param _serial_link the structural owner
 154          * @param _mem_side_port the memory-side port on the other side of the
 155          * serial_link
 156          * @param _delay the delay in cycles from receiving to sending
 157          * @param _resp_limit the size of the response queue
 158          * @param _ranges a number of address ranges to forward
 159          */
 160         SerialLinkResponsePort(const std::string& _name, SerialLink&
 161                         _serial_link, SerialLinkRequestPort& _mem_side_port,
 162                         Cycles _delay, int _resp_limit, const
 163                         std::vector<AddrRange>& _ranges);
 164
 165         /**
 166          * Queue a response packet to be sent out later and also schedule
 167          * a send if necessary.
 168          *
 169          * @param pkt a response to send out after a delay
 170          * @param when tick when response packet should be sent
 171          */
 172         void schedTimingResp(PacketPtr pkt, Tick when);
 173
 174         /**
 175          * Retry any stalled request that we have failed to accept at
 176          * an earlier point in time. This call will do nothing if no
 177          * request is waiting.
 178          */
 179         void retryStalledReq();
 180
 181       protected:
 182
 183         /** When receiving a timing request from the peer port,
 184             pass it to the serial_link. */
 185         bool recvTimingReq(PacketPtr pkt);
 186
 187         /** When receiving a retry request from the peer port,
 188             pass it to the serial_link. */
 189         void recvRespRetry();
 190
 191         /** When receiving a Atomic requestfrom the peer port,
 192             pass it to the serial_link. */
 193         Tick recvAtomic(PacketPtr pkt);
 194
 195         /** When receiving a Functional request from the peer port,
 196             pass it to the serial_link. */
 197         void recvFunctional(PacketPtr pkt);
 198
 199         /** When receiving a address range request the peer port,
 200             pass it to the serial_link. */
 201         AddrRangeList getAddrRanges() const;
 202     };
 203
 204
 205     /**
 206      * Port on the side that forwards requests and receives
 207      * responses. The memory-side port has a buffer for the requests not
 208      * yet sent.
 209      */
 210     class SerialLinkRequestPort : public RequestPort
 211     {
 212
 213       private:
 214
 215         /** The serial_link to which this port belongs. */
 216         SerialLink& serial_link;
 217
 218         /**
 219          * The response (CPU-side port) port on the other side of
 220          * the serial_link.
 221          */
 222         SerialLinkResponsePort& cpu_side_port;
 223
 224         /** Minimum delay though this serial_link. */
 225         const Cycles delay;
 226
 227         /**
 228          * Request packet queue. Request packets are held in this
 229          * queue for a specified delay to model the processing delay
 230          * of the serial_link.  We use a deque as we need to iterate over
 231          * the items for functional accesses.
 232          */
 233         std::deque<DeferredPacket> transmitList;
 234
 235         /** Max queue size for request packets */
 236         const unsigned int reqQueueLimit;
 237
 238         /**
 239          * Handle send event, scheduled when the packet at the head of
 240          * the outbound queue is ready to transmit (for timing
 241          * accesses only).
 242          */
 243         void trySendTiming();
 244
 245         /** Send event for the request queue. */
 246         EventFunctionWrapper sendEvent;
 247
 248       public:
 249
 250         /**
 251          * Constructor for the SerialLinkRequestPort.
 252          *
 253          * @param _name the port name including the owner
 254          * @param _serial_link the structural owner
 255          * @param _cpu_side_port the CPU-side port on the other
 256          * side of the serial_link
 257          * @param _delay the delay in cycles from receiving to sending
 258          * @param _req_limit the size of the request queue
 259          */
 260         SerialLinkRequestPort(const std::string& _name, SerialLink&
 261                          _serial_link, SerialLinkResponsePort& _cpu_side_port,
 262                          Cycles _delay, int _req_limit);
 263
 264         /**
 265          * Is this side blocked from accepting new request packets.
 266          *
 267          * @return true if the occupied space has reached the set limit
 268          */
 269         bool reqQueueFull() const;
 270
 271         /**
 272          * Queue a request packet to be sent out later and also schedule
 273          * a send if necessary.
 274          *
 275          * @param pkt a request to send out after a delay
 276          * @param when tick when response packet should be sent
 277          */
 278         void schedTimingReq(PacketPtr pkt, Tick when);
 279
 280         /**
 281          * Check a functional request against the packets in our
 282          * request queue.
 283          *
 284          * @param pkt packet to check against
 285          *
 286          * @return true if we find a match
 287          */
 288         bool trySatisfyFunctional(PacketPtr pkt);
 289
 290       protected:
 291
 292         /** When receiving a timing request from the peer port,
 293             pass it to the serial_link. */
 294         bool recvTimingResp(PacketPtr pkt);
 295
 296         /** When receiving a retry request from the peer port,
 297             pass it to the serial_link. */
 298         void recvReqRetry();
 299     };
 300
 301     /** Response port of the serial_link. */
 302     SerialLinkResponsePort cpu_side_port;
 303
 304     /** Request port of the serial_link. */
 305     SerialLinkRequestPort mem_side_port;
 306
 307     /** Number of parallel lanes in this serial link */
 308     unsigned num_lanes;
 309
 310     /** Speed of each link (Gb/s) in this serial link */
 311     uint64_t link_speed;
 312
 313   public:
 314
 315     Port &getPort(const std::string &if_name,
 316                   PortID idx=InvalidPortID);
 317
 318     virtual void init();
 319
 320     typedef SerialLinkParams Params;
 321
 322     SerialLink(const SerialLinkParams &p);
 323 };
 324
 325 #endif //__MEM_SERIAL_LINK_HH__