xbar.hh revision 9291 
1/*
2 * Copyright (c) 2011-2012 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 bus base class.
49 */
50
51#ifndef __MEM_BUS_HH__
52#define __MEM_BUS_HH__
53
54#include <deque>
55#include <set>
56
57#include "base/addr_range_map.hh"
58#include "base/types.hh"
59#include "mem/mem_object.hh"
60#include "params/BaseBus.hh"
61
62/**
63 * The base bus contains the common elements of the non-coherent and
64 * coherent bus. It is an abstract class that does not have any of the
65 * functionality relating to the actual reception and transmission of
66 * packets, as this is left for the subclasses.
67 *
68 * The BaseBus is responsible for the basic flow control (busy or
69 * not), the administration of retries, and the address decoding.
70 */
71class BaseBus : public MemObject
72{
73
74  protected:
75
76    /**
77     * A bus layer is an internal bus structure with its own flow
78     * control and arbitration. Hence, a single-layer bus mimics a
79     * traditional off-chip tri-state bus (like PCI), where only one
80     * set of wires are shared. For on-chip buses, a good starting
81     * point is to have three layers, for requests, responses, and
82     * snoop responses respectively (snoop requests are instantaneous
83     * and do not need any flow control or arbitration). This case is
84     * similar to AHB and some OCP configurations.
85     *
86     * As a further extensions beyond the three-layer bus, a future
87     * multi-layer bus has with one layer per connected slave port
88     * provides a full or partial crossbar, like AXI, OCP, PCIe etc.
89     *
90     * The template parameter, PortClass, indicates the destination
91     * port type for the bus. The retry list holds either master ports
92     * or slave ports, depending on the direction of the layer. Thus,
93     * a request layer has a retry list containing slave ports,
94     * whereas a response layer holds master ports.
95     */
96    template <typename PortClass>
97    class Layer
98    {
99
100      public:
101
102        /**
103         * Create a bus layer and give it a name. The bus layer uses
104         * the bus an event manager.
105         *
106         * @param _bus the bus this layer belongs to
107         * @param _name the layer's name
108         * @param _clock clock period in ticks
109         */
110        Layer(BaseBus& _bus, const std::string& _name, Tick _clock);
111
112        /**
113         * Drain according to the normal semantics, so that the bus
114         * can tell the layer to drain, and pass an event to signal
115         * back when drained.
116         *
117         * @param de drain event to call once drained
118         *
119         * @return 1 if busy or waiting to retry, or 0 if idle
120         */
121        unsigned int drain(Event *de);
122
123        /**
124         * Get the bus layer's name
125         */
126        const std::string name() const { return bus.name() + _name; }
127
128
129        /**
130         * Determine if the bus layer accepts a packet from a specific
131         * port. If not, the port in question is also added to the
132         * retry list. In either case the state of the layer is updated
133         * accordingly.
134         *
135         * @param port Source port resenting the packet
136         *
137         * @return True if the bus layer accepts the packet
138         */
139        bool tryTiming(PortClass* port);
140
141        /**
142         * Deal with a destination port accepting a packet by potentially
143         * removing the source port from the retry list (if retrying) and
144         * occupying the bus layer accordingly.
145         *
146         * @param busy_time Time to spend as a result of a successful send
147         */
148        void succeededTiming(Tick busy_time);
149
150        /**
151         * Deal with a destination port not accepting a packet by
152         * potentially adding the source port to the retry list (if
153         * not already at the front) and occupying the bus layer
154         * accordingly.
155         *
156         * @param busy_time Time to spend as a result of a failed send
157         */
158        void failedTiming(PortClass* port, Tick busy_time);
159
160        /** Occupy the bus layer until until */
161        void occupyLayer(Tick until);
162
163        /**
164         * Send a retry to the port at the head of the retryList. The
165         * caller must ensure that the list is not empty.
166         */
167        void retryWaiting();
168
169        /**
170         * Handler a retry from a neighbouring module. Eventually this
171         * should be all encapsulated in the bus. This wraps
172         * retryWaiting by verifying that there are ports waiting
173         * before calling retryWaiting.
174         */
175        void recvRetry();
176
177      private:
178
179        /** The bus this layer is a part of. */
180        BaseBus& bus;
181
182        /** A name for this layer. */
183        std::string _name;
184
185        /**
186         * We declare an enum to track the state of the bus layer. The
187         * starting point is an idle state where the bus layer is
188         * waiting for a packet to arrive. Upon arrival, the bus layer
189         * transitions to the busy state, where it remains either
190         * until the packet transfer is done, or the header time is
191         * spent. Once the bus layer leaves the busy state, it can
192         * either go back to idle, if no packets have arrived while it
193         * was busy, or the bus layer goes on to retry the first port
194         * on the retryList. A similar transition takes place from
195         * idle to retry if the bus layer receives a retry from one of
196         * its connected ports. The retry state lasts until the port
197         * in questions calls sendTiming and returns control to the
198         * bus layer, or goes to a busy state if the port does not
199         * immediately react to the retry by calling sendTiming.
200         */
201        enum State { IDLE, BUSY, RETRY };
202
203        /** track the state of the bus layer */
204        State state;
205
206        /** the clock speed for the bus layer */
207        Tick clock;
208
209        /** event for signalling when drained */
210        Event * drainEvent;
211
212        /**
213         * An array of ports that retry should be called
214         * on because the original send failed for whatever reason.
215         */
216        std::deque<PortClass*> retryList;
217
218        /**
219         * Release the bus layer after being occupied and return to an
220         * idle state where we proceed to send a retry to any
221         * potential waiting port, or drain if asked to do so.
222         */
223        void releaseLayer();
224
225        /** event used to schedule a release of the layer */
226        EventWrapper<Layer, &Layer::releaseLayer> releaseEvent;
227
228    };
229
230    /** cycles of overhead per transaction */
231    const Cycles headerCycles;
232    /** the width of the bus in bytes */
233    const uint32_t width;
234
235    typedef AddrRangeMap<PortID>::iterator PortMapIter;
236    typedef AddrRangeMap<PortID>::const_iterator PortMapConstIter;
237    AddrRangeMap<PortID> portMap;
238
239    AddrRange defaultRange;
240
241    /**
242     * Function called by the port when the bus is recieving a range change.
243     *
244     * @param master_port_id id of the port that received the change
245     */
246    void recvRangeChange(PortID master_port_id);
247
248    /** Find which port connected to this bus (if any) should be given a packet
249     * with this address.
250     * @param addr Address to find port for.
251     * @return id of port that the packet should be sent out of.
252     */
253    PortID findPort(Addr addr);
254
255    // Cache for the findPort function storing recently used ports from portMap
256    struct PortCache {
257        bool valid;
258        PortID id;
259        AddrRange range;
260    };
261
262    PortCache portCache[3];
263
264    // Checks the cache and returns the id of the port that has the requested
265    // address within its range
266    inline PortID checkPortCache(Addr addr) const {
267        if (portCache[0].valid && portCache[0].range == addr) {
268            return portCache[0].id;
269        }
270        if (portCache[1].valid && portCache[1].range == addr) {
271            return portCache[1].id;
272        }
273        if (portCache[2].valid && portCache[2].range == addr) {
274            return portCache[2].id;
275        }
276
277        return InvalidPortID;
278    }
279
280    // Clears the earliest entry of the cache and inserts a new port entry
281    inline void updatePortCache(short id, const AddrRange& range) {
282        portCache[2].valid = portCache[1].valid;
283        portCache[2].id    = portCache[1].id;
284        portCache[2].range = portCache[1].range;
285
286        portCache[1].valid = portCache[0].valid;
287        portCache[1].id    = portCache[0].id;
288        portCache[1].range = portCache[0].range;
289
290        portCache[0].valid = true;
291        portCache[0].id    = id;
292        portCache[0].range = range;
293    }
294
295    // Clears the cache. Needs to be called in constructor.
296    inline void clearPortCache() {
297        portCache[2].valid = false;
298        portCache[1].valid = false;
299        portCache[0].valid = false;
300    }
301
302    /**
303     * Return the address ranges the bus is responsible for.
304     *
305     * @return a list of non-overlapping address ranges
306     */
307    AddrRangeList getAddrRanges() const;
308
309    /** Calculate the timing parameters for the packet.  Updates the
310     * firstWordTime and finishTime fields of the packet object.
311     * Returns the tick at which the packet header is completed (which
312     * will be all that is sent if the target rejects the packet).
313     */
314    Tick calcPacketTiming(PacketPtr pkt);
315
316    /**
317     * Ask everyone on the bus what their size is and determine the
318     * bus size as either the maximum, or if no device specifies a
319     * block size return the default.
320     *
321     * @return the max of all the sizes or the default if none is set
322     */
323    unsigned deviceBlockSize() const;
324
325    /**
326     * Remember for each of the master ports of the bus if we got an
327     * address range from the connected slave. For convenience, also
328     * keep track of if we got ranges from all the slave modules or
329     * not.
330     */
331    std::vector<bool> gotAddrRanges;
332    bool gotAllAddrRanges;
333
334    /** The master and slave ports of the bus */
335    std::vector<SlavePort*> slavePorts;
336    std::vector<MasterPort*> masterPorts;
337
338    /** Convenience typedefs. */
339    typedef std::vector<SlavePort*>::iterator SlavePortIter;
340    typedef std::vector<MasterPort*>::iterator MasterPortIter;
341    typedef std::vector<SlavePort*>::const_iterator SlavePortConstIter;
342    typedef std::vector<MasterPort*>::const_iterator MasterPortConstIter;
343
344    /** Port that handles requests that don't match any of the interfaces.*/
345    PortID defaultPortID;
346
347    /** If true, use address range provided by default device.  Any
348       address not handled by another port and not in default device's
349       range will cause a fatal error.  If false, just send all
350       addresses not handled by another port to default device. */
351    const bool useDefaultRange;
352
353    uint32_t blockSize;
354
355    BaseBus(const BaseBusParams *p);
356
357    virtual ~BaseBus();
358
359  public:
360
361    virtual void init();
362
363    /** A function used to return the port associated with this bus object. */
364    virtual MasterPort& getMasterPort(const std::string& if_name, int idx = -1);
365    virtual SlavePort& getSlavePort(const std::string& if_name, int idx = -1);
366
367    virtual unsigned int drain(Event *de) = 0;
368
369};
370
371#endif //__MEM_BUS_HH__
372