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31 #ifndef __MEM_TPORT_HH__
32 #define __MEM_TPORT_HH__
37 * Declaration of SimpleTimingPort.
43 #include "mem/port.hh"
44 #include "sim/eventq.hh"
47 * A simple port for interfacing objects that basically have only
48 * functional memory behavior (e.g. I/O devices) to the memory system.
49 * Both timing and functional accesses are implemented in terms of
50 * atomic accesses. A derived port class thus only needs to provide
51 * recvAtomic() to support all memory access modes.
53 * The tricky part is handling recvTiming(), where the response must
54 * be scheduled separately via a later call to sendTiming(). This
55 * feature is handled by scheduling an internal event that calls
56 * sendTiming() after a delay, and optionally rescheduling the
57 * response if it is nacked.
59 class SimpleTimingPort : public Port
62 /** A deferred packet, buffered to transmit later. */
63 class DeferredPacket {
65 Tick tick; ///< The tick when the packet is ready to transmit
66 PacketPtr pkt; ///< Pointer to the packet to transmit
67 DeferredPacket(Tick t, PacketPtr p)
72 typedef std::list<DeferredPacket> DeferredPacketList;
73 typedef std::list<DeferredPacket>::iterator DeferredPacketIterator;
75 /** A list of outgoing timing response packets that haven't been
77 DeferredPacketList transmitList;
79 /** This function attempts to send deferred packets. Scheduled to
80 * be called in the future via SendEvent. */
81 void processSendEvent();
84 * This class is used to implemented sendTiming() with a delay. When
85 * a delay is requested a the event is scheduled if it isn't already.
86 * When the event time expires it attempts to send the packet.
87 * If it cannot, the packet sent when recvRetry() is called.
91 /** If we need to drain, keep the drain event around until we're done
95 /** Remember whether we're awaiting a retry from the bus. */
98 /** Check the list of buffered packets against the supplied
99 * functional request. */
100 bool checkFunctional(PacketPtr funcPkt);
102 /** Check whether we have a packet ready to go on the transmit list. */
103 bool deferredPacketReady()
104 { return !transmitList.empty() && transmitList.front().tick <= curTick(); }
106 Tick deferredPacketReadyTime()
107 { return transmitList.empty() ? MaxTick : transmitList.front().tick; }
110 schedSendEvent(Tick when)
112 if (waitingOnRetry) {
113 assert(!sendEvent->scheduled());
117 if (!sendEvent->scheduled()) {
118 schedule(sendEvent, when);
119 } else if (sendEvent->when() > when) {
120 reschedule(sendEvent, when);
125 /** Schedule a sendTiming() event to be called in the future.
126 * @param pkt packet to send
127 * @param absolute time (in ticks) to send packet
129 void schedSendTiming(PacketPtr pkt, Tick when);
131 /** Attempt to send the packet at the head of the deferred packet
132 * list. Caller must guarantee that the deferred packet list is
133 * non-empty and that the head packet is scheduled for curTick() (or
136 void sendDeferredPacket();
138 /** This function is notification that the device should attempt to send a
140 virtual void recvRetry();
142 /** Implemented using recvAtomic(). */
143 void recvFunctional(PacketPtr pkt);
145 /** Implemented using recvAtomic(). */
146 bool recvTiming(PacketPtr pkt);
149 * Simple ports generally don't care about any status
150 * changes... can always override this in cases where that's not
152 virtual void recvStatusChange(Status status) { }
156 SimpleTimingPort(std::string pname, MemObject *_owner);
159 /** Hook for draining timing accesses from the system. The
160 * associated SimObject's drain() functions should be implemented
161 * something like this when this class is used:
163 PioDevice::drain(Event *de)
166 count = SimpleTimingPort->drain(de);
168 changeState(Draining);
170 changeState(Drained);
175 unsigned int drain(Event *de);
178 #endif // __MEM_TPORT_HH__