1/* 2 * Copyright (c) 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
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45#define __MEM_TPORT_HH__ 46 47/** 48 * @file 49 * 50 * Declaration of SimpleTimingPort. 51 */ 52
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53#include <list>
54#include <string>
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53#include "mem/qport.hh" |
54
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56#include "mem/port.hh"
57#include "sim/eventq.hh"
58
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55/**
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60 * A simple port for interfacing objects that basically have only
61 * functional memory behavior (e.g. I/O devices) to the memory system.
62 * Both timing and functional accesses are implemented in terms of
63 * atomic accesses. A derived port class thus only needs to provide
64 * recvAtomic() to support all memory access modes.
65 *
66 * The tricky part is handling recvTiming(), where the response must
67 * be scheduled separately via a later call to sendTiming(). This
68 * feature is handled by scheduling an internal event that calls
69 * sendTiming() after a delay, and optionally rescheduling the
70 * response if it is nacked.
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56 * The simple timing port uses a queued port to implement 57 * recvFunctional and recvTiming through recvAtomic. It is always a 58 * slave port. |
59 */
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72class SimpleTimingPort : public Port
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60class SimpleTimingPort : public QueuedPort |
61{
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62 |
63 protected:
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75 /** A deferred packet, buffered to transmit later. */
76 class DeferredPacket {
77 public:
78 Tick tick; ///< The tick when the packet is ready to transmit
79 PacketPtr pkt; ///< Pointer to the packet to transmit
80 DeferredPacket(Tick t, PacketPtr p)
81 : tick(t), pkt(p)
82 {}
83 };
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64
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85 typedef std::list<DeferredPacket> DeferredPacketList;
86 typedef std::list<DeferredPacket>::iterator DeferredPacketIterator;
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65 /** The packet queue used to store outgoing responses. */ 66 PacketQueue queue; |
67
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88 /** A list of outgoing timing response packets that haven't been
89 * serviced yet. */
90 DeferredPacketList transmitList;
91
92 /** Label to use for print request packets label stack. */
93 const std::string label;
94
95 /** This function attempts to send deferred packets. Scheduled to
96 * be called in the future via SendEvent. */
97 void processSendEvent();
98
99 /**
100 * This class is used to implemented sendTiming() with a delay. When
101 * a delay is requested a the event is scheduled if it isn't already.
102 * When the event time expires it attempts to send the packet.
103 * If it cannot, the packet sent when recvRetry() is called.
104 **/
105 EventWrapper<SimpleTimingPort,
106 &SimpleTimingPort::processSendEvent> sendEvent;
107
108 /** If we need to drain, keep the drain event around until we're done
109 * here.*/
110 Event *drainEvent;
111
112 /** Remember whether we're awaiting a retry from the bus. */
113 bool waitingOnRetry;
114
115 /** Check whether we have a packet ready to go on the transmit list. */
116 bool deferredPacketReady()
117 { return !transmitList.empty() && transmitList.front().tick <= curTick(); }
118
119 Tick deferredPacketReadyTime()
120 { return transmitList.empty() ? MaxTick : transmitList.front().tick; }
121
122 /**
123 * Schedule a send even if not already waiting for a retry. If the
124 * requested time is before an already scheduled send event it
125 * will be rescheduled.
126 *
127 * @param when
128 */
129 void schedSendEvent(Tick when);
130
131 /** Schedule a sendTiming() event to be called in the future.
132 * @param pkt packet to send
133 * @param absolute time (in ticks) to send packet
134 */
135 void schedSendTiming(PacketPtr pkt, Tick when);
136
137 /** Attempt to send the packet at the head of the deferred packet
138 * list. Caller must guarantee that the deferred packet list is
139 * non-empty and that the head packet is scheduled for curTick() (or
140 * earlier).
141 */
142 virtual void sendDeferredPacket();
143
144 /**
145 * Attempt to send the packet at the front of the transmit list,
146 * and set waitingOnRetry accordingly. The packet is temporarily
147 * taken off the list, but put back at the front if not
148 * successfully sent.
149 */
150 void trySendTiming();
151
152 /**
153 * Based on the transmit list, or the provided time, schedule a
154 * send event if there are packets to send. If we are idle and
155 * asked to drain then do so.
156 *
157 * @param time an alternative time for the next send event
158 */
159 void scheduleSend(Tick time = MaxTick);
160
161 /** This function is notification that the device should attempt to send a
162 * packet again. */
163 virtual void recvRetry();
164
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68 /** Implemented using recvAtomic(). */ 69 void recvFunctional(PacketPtr pkt); 70 71 /** Implemented using recvAtomic(). */ 72 bool recvTiming(PacketPtr pkt); 73
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171 /**
172 * Simple ports are generally used as slave ports (i.e. the
173 * respond to requests) and thus do not expect to receive any
174 * range changes (as the neighbouring port has a master role and
175 * do not have any address ranges. A subclass can override the
176 * default behaviuor if needed.
177 */
178 virtual void recvRangeChange() { }
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74 virtual Tick recvAtomic(PacketPtr pkt) = 0; |
75
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180
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76 public:
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182 SimpleTimingPort(const std::string &_name, MemObject *_owner,
183 const std::string _label = "SimpleTimingPort");
184 ~SimpleTimingPort();
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77
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186 /** Check the list of buffered packets against the supplied
187 * functional request. */
188 bool checkFunctional(PacketPtr pkt);
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78 /** 79 * Create a new SimpleTimingPort that relies on a packet queue to 80 * hold responses, and implements recvTiming and recvFunctional 81 * through calls to recvAtomic. Once a request arrives, it is 82 * passed to recvAtomic, and in the case of a timing access any 83 * response is scheduled to be sent after the delay of the atomic 84 * operation. 85 * 86 * @param name port name 87 * @param owner structural owner 88 */ 89 SimpleTimingPort(const std::string& name, MemObject* owner); |
90
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190 /** Hook for draining timing accesses from the system. The
191 * associated SimObject's drain() functions should be implemented
192 * something like this when this class is used:
193 \code
194 PioDevice::drain(Event *de)
195 {
196 unsigned int count;
197 count = SimpleTimingPort->drain(de);
198 if (count)
199 changeState(Draining);
200 else
201 changeState(Drained);
202 return count;
203 }
204 \endcode
205 */
206 unsigned int drain(Event *de);
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91 virtual ~SimpleTimingPort() { } 92 |
93}; 94 95#endif // __MEM_TPORT_HH__
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