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31 #ifndef __MEM_TPORT_HH__
32 #define __MEM_TPORT_HH__
37 * Declaration of SimpleTimingPort.
40 #include "mem/port.hh"
41 #include "sim/eventq.hh"
46 * A simple port for interfacing objects that basically have only
47 * functional memory behavior (e.g. I/O devices) to the memory system.
48 * Both timing and functional accesses are implemented in terms of
49 * atomic accesses. A derived port class thus only needs to provide
50 * recvAtomic() to support all memory access modes.
52 * The tricky part is handling recvTiming(), where the response must
53 * be scheduled separately via a later call to sendTiming(). This
54 * feature is handled by scheduling an internal event that calls
55 * sendTiming() after a delay, and optionally rescheduling the
56 * response if it is nacked.
58 class SimpleTimingPort : public Port
61 /** A deferred packet, buffered to transmit later. */
62 class DeferredPacket {
64 Tick tick; ///< The tick when the packet is ready to transmit
65 PacketPtr pkt; ///< Pointer to the packet to transmit
66 DeferredPacket(Tick t, PacketPtr p)
71 typedef std::list<DeferredPacket> DeferredPacketList;
72 typedef std::list<DeferredPacket>::iterator DeferredPacketIterator;
74 /** A list of outgoing timing response packets that haven't been
76 DeferredPacketList transmitList;
78 /** This function attempts to send deferred packets. Scheduled to
79 * be called in the future via SendEvent. */
80 void processSendEvent();
83 * This class is used to implemented sendTiming() with a delay. When
84 * a delay is requested a the event is scheduled if it isn't already.
85 * When the event time expires it attempts to send the packet.
86 * If it cannot, the packet sent when recvRetry() is called.
90 /** If we need to drain, keep the drain event around until we're done
94 /** Remember whether we're awaiting a retry from the bus. */
97 /** Check the list of buffered packets against the supplied
98 * functional request. */
99 bool checkFunctional(PacketPtr funcPkt);
101 /** Check whether we have a packet ready to go on the transmit list. */
102 bool deferredPacketReady()
103 { return !transmitList.empty() && transmitList.front().tick <= curTick; }
105 Tick deferredPacketReadyTime()
106 { return transmitList.empty() ? MaxTick : transmitList.front().tick; }
109 schedSendEvent(Tick when)
111 if (waitingOnRetry) {
112 assert(!sendEvent->scheduled());
116 if (!sendEvent->scheduled()) {
117 schedule(sendEvent, when);
118 } else if (sendEvent->when() > when) {
119 reschedule(sendEvent, when);
124 /** Schedule a sendTiming() event to be called in the future.
125 * @param pkt packet to send
126 * @param absolute time (in ticks) to send packet
128 void schedSendTiming(PacketPtr pkt, Tick when);
130 /** Attempt to send the packet at the head of the deferred packet
131 * list. Caller must guarantee that the deferred packet list is
132 * non-empty and that the head packet is scheduled for curTick (or
135 void sendDeferredPacket();
137 /** This function is notification that the device should attempt to send a
139 virtual void recvRetry();
141 /** Implemented using recvAtomic(). */
142 void recvFunctional(PacketPtr pkt);
144 /** Implemented using recvAtomic(). */
145 bool recvTiming(PacketPtr pkt);
148 * Simple ports generally don't care about any status
149 * changes... can always override this in cases where that's not
151 virtual void recvStatusChange(Status status) { }
155 SimpleTimingPort(std::string pname, MemObject *_owner);
158 /** Hook for draining timing accesses from the system. The
159 * associated SimObject's drain() functions should be implemented
160 * something like this when this class is used:
162 PioDevice::drain(Event *de)
165 count = SimpleTimingPort->drain(de);
167 changeState(Draining);
169 changeState(Drained);
174 unsigned int drain(Event *de);
177 #endif // __MEM_TPORT_HH__