coherent_xbar.hh revision 10405:7a618c07e663 
1/*
2 * Copyright (c) 2011-2014 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
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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 a coherent crossbar.
49 */
50
51#ifndef __MEM_COHERENT_XBAR_HH__
52#define __MEM_COHERENT_XBAR_HH__
53
54#include "base/hashmap.hh"
55#include "mem/snoop_filter.hh"
56#include "mem/xbar.hh"
57#include "params/CoherentXBar.hh"
58
59/**
60 * A coherent crossbar connects a number of (potentially) snooping
61 * masters and slaves, and routes the request and response packets
62 * based on the address, and also forwards all requests to the
63 * snoopers and deals with the snoop responses.
64 *
65 * The coherent crossbar can be used as a template for modelling QPI,
66 * HyperTransport, ACE and coherent OCP buses, and is typically used
67 * for the L1-to-L2 buses and as the main system interconnect.  @sa
68 * \ref gem5MemorySystem "gem5 Memory System"
69 */
70class CoherentXBar : public BaseXBar
71{
72
73  protected:
74
75    /**
76     * Declare the layers of this crossbar, one vector for requests,
77     * one for responses, and one for snoop responses
78     */
79    typedef Layer<SlavePort,MasterPort> ReqLayer;
80    typedef Layer<MasterPort,SlavePort> RespLayer;
81    typedef Layer<SlavePort,MasterPort> SnoopLayer;
82    std::vector<ReqLayer*> reqLayers;
83    std::vector<RespLayer*> respLayers;
84    std::vector<SnoopLayer*> snoopLayers;
85
86    /**
87     * Declaration of the coherent crossbar slave port type, one will
88     * be instantiated for each of the master ports connecting to the
89     * crossbar.
90     */
91    class CoherentXBarSlavePort : public SlavePort
92    {
93
94      private:
95
96        /** A reference to the crossbar to which this port belongs. */
97        CoherentXBar &xbar;
98
99      public:
100
101        CoherentXBarSlavePort(const std::string &_name,
102                             CoherentXBar &_xbar, PortID _id)
103            : SlavePort(_name, &_xbar, _id), xbar(_xbar)
104        { }
105
106      protected:
107
108        /**
109         * When receiving a timing request, pass it to the crossbar.
110         */
111        virtual bool recvTimingReq(PacketPtr pkt)
112        { return xbar.recvTimingReq(pkt, id); }
113
114        /**
115         * When receiving a timing snoop response, pass it to the crossbar.
116         */
117        virtual bool recvTimingSnoopResp(PacketPtr pkt)
118        { return xbar.recvTimingSnoopResp(pkt, id); }
119
120        /**
121         * When receiving an atomic request, pass it to the crossbar.
122         */
123        virtual Tick recvAtomic(PacketPtr pkt)
124        { return xbar.recvAtomic(pkt, id); }
125
126        /**
127         * When receiving a functional request, pass it to the crossbar.
128         */
129        virtual void recvFunctional(PacketPtr pkt)
130        { xbar.recvFunctional(pkt, id); }
131
132        /**
133         * When receiving a retry, pass it to the crossbar.
134         */
135        virtual void recvRetry()
136        { panic("Crossbar slave ports should never retry.\n"); }
137
138        /**
139         * Return the union of all adress ranges seen by this crossbar.
140         */
141        virtual AddrRangeList getAddrRanges() const
142        { return xbar.getAddrRanges(); }
143
144    };
145
146    /**
147     * Declaration of the coherent crossbar master port type, one will be
148     * instantiated for each of the slave interfaces connecting to the
149     * crossbar.
150     */
151    class CoherentXBarMasterPort : public MasterPort
152    {
153      private:
154        /** A reference to the crossbar to which this port belongs. */
155        CoherentXBar &xbar;
156
157      public:
158
159        CoherentXBarMasterPort(const std::string &_name,
160                              CoherentXBar &_xbar, PortID _id)
161            : MasterPort(_name, &_xbar, _id), xbar(_xbar)
162        { }
163
164      protected:
165
166        /**
167         * Determine if this port should be considered a snooper. For
168         * a coherent crossbar master port this is always true.
169         *
170         * @return a boolean that is true if this port is snooping
171         */
172        virtual bool isSnooping() const
173        { return true; }
174
175        /**
176         * When receiving a timing response, pass it to the crossbar.
177         */
178        virtual bool recvTimingResp(PacketPtr pkt)
179        { return xbar.recvTimingResp(pkt, id); }
180
181        /**
182         * When receiving a timing snoop request, pass it to the crossbar.
183         */
184        virtual void recvTimingSnoopReq(PacketPtr pkt)
185        { return xbar.recvTimingSnoopReq(pkt, id); }
186
187        /**
188         * When receiving an atomic snoop request, pass it to the crossbar.
189         */
190        virtual Tick recvAtomicSnoop(PacketPtr pkt)
191        { return xbar.recvAtomicSnoop(pkt, id); }
192
193        /**
194         * When receiving a functional snoop request, pass it to the crossbar.
195         */
196        virtual void recvFunctionalSnoop(PacketPtr pkt)
197        { xbar.recvFunctionalSnoop(pkt, id); }
198
199        /** When reciving a range change from the peer port (at id),
200            pass it to the crossbar. */
201        virtual void recvRangeChange()
202        { xbar.recvRangeChange(id); }
203
204        /** When reciving a retry from the peer port (at id),
205            pass it to the crossbar. */
206        virtual void recvRetry()
207        { xbar.recvRetry(id); }
208
209    };
210
211    /**
212     * Internal class to bridge between an incoming snoop response
213     * from a slave port and forwarding it through an outgoing slave
214     * port. It is effectively a dangling master port.
215     */
216    class SnoopRespPort : public MasterPort
217    {
218
219      private:
220
221        /** The port which we mirror internally. */
222        SlavePort& slavePort;
223
224      public:
225
226        /**
227         * Create a snoop response port that mirrors a given slave port.
228         */
229        SnoopRespPort(SlavePort& slave_port, CoherentXBar& _xbar) :
230            MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
231            slavePort(slave_port) { }
232
233        /**
234         * Override the sending of retries and pass them on through
235         * the mirrored slave port.
236         */
237        void sendRetry() {
238            slavePort.sendRetry();
239        }
240
241        /**
242         * Provided as necessary.
243         */
244        void recvRetry() { panic("SnoopRespPort should never see retry\n"); }
245
246        /**
247         * Provided as necessary.
248         */
249        bool recvTimingResp(PacketPtr pkt)
250        {
251            panic("SnoopRespPort should never see timing response\n");
252            return false;
253        }
254
255    };
256
257    std::vector<SnoopRespPort*> snoopRespPorts;
258
259    std::vector<SlavePort*> snoopPorts;
260
261    /**
262     * Store the outstanding requests so we can determine which ones
263     * we generated and which ones were merely forwarded. This is used
264     * in the coherent crossbar when coherency responses come back.
265     */
266    m5::hash_set<RequestPtr> outstandingReq;
267
268    /**
269     * Keep a pointer to the system to be allow to querying memory system
270     * properties.
271     */
272    System *system;
273
274    /** A snoop filter that tracks cache line residency and can restrict the
275      * broadcast needed for probes.  NULL denotes an absent filter. */
276    SnoopFilter *snoopFilter;
277
278    /** Function called by the port when the crossbar is recieving a Timing
279      request packet.*/
280    bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
281
282    /** Function called by the port when the crossbar is recieving a Timing
283      response packet.*/
284    bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
285
286    /** Function called by the port when the crossbar is recieving a timing
287        snoop request.*/
288    void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
289
290    /** Function called by the port when the crossbar is recieving a timing
291        snoop response.*/
292    bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
293
294    /** Timing function called by port when it is once again able to process
295     * requests. */
296    void recvRetry(PortID master_port_id);
297
298    /**
299     * Forward a timing packet to our snoopers, potentially excluding
300     * one of the connected coherent masters to avoid sending a packet
301     * back to where it came from.
302     *
303     * @param pkt Packet to forward
304     * @param exclude_slave_port_id Id of slave port to exclude
305     */
306    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) {
307        forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
308    }
309
310    /**
311     * Forward a timing packet to a selected list of snoopers, potentially
312     * excluding one of the connected coherent masters to avoid sending a packet
313     * back to where it came from.
314     *
315     * @param pkt Packet to forward
316     * @param exclude_slave_port_id Id of slave port to exclude
317     * @param dests Vector of destination ports for the forwarded pkt
318     */
319    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
320                       const std::vector<SlavePort*>& dests);
321
322    /** Function called by the port when the crossbar is recieving a Atomic
323      transaction.*/
324    Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
325
326    /** Function called by the port when the crossbar is recieving an
327        atomic snoop transaction.*/
328    Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);
329
330    /**
331     * Forward an atomic packet to our snoopers, potentially excluding
332     * one of the connected coherent masters to avoid sending a packet
333     * back to where it came from.
334     *
335     * @param pkt Packet to forward
336     * @param exclude_slave_port_id Id of slave port to exclude
337     *
338     * @return a pair containing the snoop response and snoop latency
339     */
340    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
341                                          PortID exclude_slave_port_id)
342    {
343        return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID, snoopPorts);
344    }
345
346    /**
347     * Forward an atomic packet to a selected list of snoopers, potentially
348     * excluding one of the connected coherent masters to avoid sending a packet
349     * back to where it came from.
350     *
351     * @param pkt Packet to forward
352     * @param exclude_slave_port_id Id of slave port to exclude
353     * @param source_master_port_id Id of the master port for snoops from below
354     * @param dests Vector of destination ports for the forwarded pkt
355     *
356     * @return a pair containing the snoop response and snoop latency
357     */
358    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
359                                          PortID exclude_slave_port_id,
360                                          PortID source_master_port_id,
361                                          const std::vector<SlavePort*>& dests);
362
363    /** Function called by the port when the crossbar is recieving a Functional
364        transaction.*/
365    void recvFunctional(PacketPtr pkt, PortID slave_port_id);
366
367    /** Function called by the port when the crossbar is recieving a functional
368        snoop transaction.*/
369    void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
370
371    /**
372     * Forward a functional packet to our snoopers, potentially
373     * excluding one of the connected coherent masters to avoid
374     * sending a packet back to where it came from.
375     *
376     * @param pkt Packet to forward
377     * @param exclude_slave_port_id Id of slave port to exclude
378     */
379    void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
380
381    Stats::Scalar snoops;
382    Stats::Distribution snoopFanout;
383
384  public:
385
386    virtual void init();
387
388    CoherentXBar(const CoherentXBarParams *p);
389
390    virtual ~CoherentXBar();
391
392    unsigned int drain(DrainManager *dm);
393
394    virtual void regStats();
395};
396
397#endif //__MEM_COHERENT_XBAR_HH__
398