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