* @file Definition of a simple bus bridge without buffering.
*/
+#include <algorithm>
#include "base/trace.hh"
#include "mem/bridge.hh"
#include "sim/builder.hh"
+Bridge::BridgePort::BridgePort(const std::string &_name,
+ Bridge *_bridge, BridgePort *_otherPort,
+ int _delay, int _queueLimit)
+ : Port(_name), bridge(_bridge), otherPort(_otherPort),
+ delay(_delay), outstandingResponses(0),
+ queueLimit(_queueLimit), sendEvent(this)
+{
+}
+
+Bridge::Bridge(const std::string &n, int qsa, int qsb,
+ Tick _delay, int write_ack)
+ : MemObject(n),
+ portA(n + "-portA", this, &portB, _delay, qsa),
+ portB(n + "-portB", this, &portA, _delay, qsa),
+ ackWrites(write_ack)
+{
+}
+
+Port *
+Bridge::getPort(const std::string &if_name)
+{
+ BridgePort *port;
+
+ if (if_name == "side_a")
+ port = &portA;
+ else if (if_name == "side_b")
+ port = &portB;
+ else
+ return NULL;
+
+ if (port->getPeer() != NULL)
+ panic("bridge side %s already connected to.", if_name);
+ return port;
+}
+
+
void
Bridge::init()
{
// Make sure that both sides are connected to.
- if (sideA == NULL || sideB == NULL)
+ if (portA.getPeer() == NULL || portB.getPeer() == NULL)
panic("Both ports of bus bridge are not connected to a bus.\n");
}
-/** Function called by the port when the bus is recieving a Timing
+/** Function called by the port when the bus is receiving a Timing
* transaction.*/
bool
-Bridge::recvTiming(Packet *pkt, Side id)
+Bridge::BridgePort::recvTiming(Packet *pkt)
{
- if (blockedA && id == SideA)
- return false;
- if (blockedB && id == SideB)
- return false;
-
- if (delay) {
- if (!sendEvent.scheduled())
- sendEvent.schedule(curTick + delay);
- if (id == SideA) {
- inboundA.push_back(std::make_pair<Packet*, Tick>(pkt, curTick));
- blockCheck(SideA);
- } else {
- inboundB.push_back(std::make_pair<Packet*, Tick>(pkt, curTick));
- blockCheck(SideB);
- }
- } else {
- if (id == SideB) {
- sideA->sendPkt(pkt);
- blockCheck(SideB);
- } else {
- sideB->sendPkt(pkt);
- blockCheck(SideA);
- }
+ DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
+ pkt->getSrc(), pkt->getDest(), pkt->getAddr());
+
+ if (pkt->isResponse()) {
+ // This is a response for a request we forwarded earlier. The
+ // corresponding PacketBuffer should be stored in the packet's
+ // senderState field.
+ PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
+ assert(buf != NULL);
+ // set up new packet dest & senderState based on values saved
+ // from original request
+ buf->fixResponse(pkt);
+ DPRINTF(BusBridge, " is response, new dest %d\n", pkt->getDest());
+ delete buf;
}
- return true;
+ return otherPort->queueForSendTiming(pkt);
}
-void
-Bridge::blockCheck(Side id)
-{
- /* Check that we still have buffer space available. */
- if (id == SideB) {
- if (sideA->numQueued() + inboundB.size() >= queueSizeA && !blockedB) {
- sideB->sendStatusChange(Port::Blocked);
- blockedB = true;
- } else if (sideA->numQueued() + inboundB.size() < queueSizeA && blockedB) {
- sideB->sendStatusChange(Port::Unblocked);
- blockedB = false;
- }
- } else {
- if (sideB->numQueued() + inboundA.size() >= queueSizeB && !blockedA) {
- sideA->sendStatusChange(Port::Blocked);
- blockedA = true;
- } else if (sideB->numQueued() + inboundA.size() < queueSizeB && blockedA) {
- sideA->sendStatusChange(Port::Unblocked);
- blockedA = false;
- }
- }
-}
-void Bridge::timerEvent()
+bool
+Bridge::BridgePort::queueForSendTiming(Packet *pkt)
{
- Tick t = 0;
+ if (queueFull())
+ return false;
- assert(inboundA.size() || inboundB.size());
- if (inboundA.size()) {
- while (inboundA.front().second <= curTick + delay){
- sideB->sendPkt(inboundA.front());
- inboundA.pop_front();
- }
- if (inboundA.size())
- t = inboundA.front().second + delay;
- }
- if (inboundB.size()) {
- while (inboundB.front().second <= curTick + delay){
- sideB->sendPkt(inboundA.front());
- inboundB.pop_front();
- }
- if (inboundB.size())
- if (t == 0)
- t = inboundB.front().second + delay;
- else
- t = std::min(t,inboundB.front().second + delay);
- } else {
- panic("timerEvent() called but nothing to do?");
+ Tick readyTime = curTick + delay;
+ PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
+
+ // If we're about to put this packet at the head of the queue, we
+ // need to schedule an event to do the transmit. Otherwise there
+ // should already be an event scheduled for sending the head
+ // packet.
+ if (sendQueue.empty()) {
+ sendEvent.schedule(readyTime);
}
- if (t != 0)
- sendEvent.schedule(t);
+ sendQueue.push_back(buf);
+
+ // Did we just become blocked? If yes, let other side know.
+ if (queueFull())
+ otherPort->sendStatusChange(Port::Blocked);
+
+ return true;
}
void
-Bridge::BridgePort::sendPkt(Packet *pkt)
+Bridge::BridgePort::finishSend(PacketBuffer *buf)
{
- if (!sendTiming(pkt))
- outbound.push_back(std::make_pair<Packet*,Tick>(pkt, curTick));
+ if (buf->expectResponse) {
+ // Must wait for response. We just need to count outstanding
+ // responses (in case we want to cap them); PacketBuffer
+ // pointer will be recovered on response.
+ ++outstandingResponses;
+ DPRINTF(BusBridge, " successful: awaiting response (%d)\n",
+ outstandingResponses);
+ } else {
+ // no response expected... deallocate packet buffer now.
+ DPRINTF(BusBridge, " successful: no response expected\n");
+ delete buf;
+ }
+
+ // If there are more packets to send, schedule event to try again.
+ if (!sendQueue.empty()) {
+ buf = sendQueue.front();
+ sendEvent.schedule(std::max(buf->ready, curTick + 1));
+ }
}
+
void
-Bridge::BridgePort::sendPkt(std::pair<Packet*, Tick> p)
+Bridge::BridgePort::trySend()
{
- if (!sendTiming(p.first))
- outbound.push_back(p);
+ assert(!sendQueue.empty());
+
+ PacketBuffer *buf = sendQueue.front();
+
+ assert(buf->ready <= curTick);
+
+ Packet *pkt = buf->pkt;
+
+ DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
+ buf->origSrc, pkt->getDest(), pkt->getAddr());
+
+ if (sendTiming(pkt)) {
+ // send successful
+ sendQueue.pop_front();
+ buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
+ finishSend(buf);
+ } else {
+ DPRINTF(BusBridge, " unsuccessful\n");
+ }
}
Packet *
Bridge::BridgePort::recvRetry()
{
- Packet *pkt;
- assert(outbound.size() > 0);
- assert(outbound.front().second >= curTick + bridge->delay);
- pkt = outbound.front().first;
- outbound.pop_front();
- bridge->blockCheck(side);
+ PacketBuffer *buf = sendQueue.front();
+ Packet *pkt = buf->pkt;
+ finishSend(buf);
return pkt;
}
-/** Function called by the port when the bus is recieving a Atomic
+/** Function called by the port when the bus is receiving a Atomic
* transaction.*/
Tick
-Bridge::recvAtomic(Packet *pkt, Side id)
+Bridge::BridgePort::recvAtomic(Packet *pkt)
{
- pkt->time += delay;
-
- if (id == SideA)
- return sideB->sendAtomic(pkt);
- else
- return sideA->sendAtomic(pkt);
+ return otherPort->sendAtomic(pkt) + delay;
}
-/** Function called by the port when the bus is recieving a Functional
+/** Function called by the port when the bus is receiving a Functional
* transaction.*/
void
-Bridge::recvFunctional(Packet *pkt, Side id)
+Bridge::BridgePort::recvFunctional(Packet *pkt)
{
- pkt->time += delay;
- std::list<std::pair<Packet*, Tick> >::iterator i;
+ std::list<PacketBuffer*>::iterator i;
bool pktContinue = true;
- for(i = inboundA.begin(); i != inboundA.end(); ++i) {
- if (pkt->intersect(i->first)) {
- pktContinue &= fixPacket(pkt, i->first);
- }
- }
-
- for(i = inboundB.begin(); i != inboundB.end(); ++i) {
- if (pkt->intersect(i->first)) {
- pktContinue &= fixPacket(pkt, i->first);
- }
- }
-
- for(i = sideA->outbound.begin(); i != sideA->outbound.end(); ++i) {
- if (pkt->intersect(i->first)) {
- pktContinue &= fixPacket(pkt, i->first);
- }
- }
-
- for(i = sideB->outbound.begin(); i != sideB->outbound.end(); ++i) {
- if (pkt->intersect(i->first)) {
- pktContinue &= fixPacket(pkt, i->first);
+ for (i = sendQueue.begin(); i != sendQueue.end(); ++i) {
+ if (pkt->intersect((*i)->pkt)) {
+ pktContinue &= fixPacket(pkt, (*i)->pkt);
}
}
if (pktContinue) {
- if (id == SideA)
- sideB->sendFunctional(pkt);
- else
- sideA->sendFunctional(pkt);
+ otherPort->sendFunctional(pkt);
}
}
-/** Function called by the port when the bus is recieving a status change.*/
+/** Function called by the port when the bus is receiving a status change.*/
void
-Bridge::recvStatusChange(Port::Status status, Side id)
+Bridge::BridgePort::recvStatusChange(Port::Status status)
{
if (status == Port::Blocked || status == Port::Unblocked)
- return ;
+ return;
- if (id == SideA)
- sideB->sendStatusChange(status);
- else
- sideA->sendStatusChange(status);
+ otherPort->sendStatusChange(status);
}
void
-Bridge::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, Side id)
+Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
+ AddrRangeList &snoop)
{
- if (id == SideA)
- sideB->getPeerAddressRanges(resp, snoop);
- else
- sideA->getPeerAddressRanges(resp, snoop);
+ otherPort->getPeerAddressRanges(resp, snoop);
}
BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
class Bridge : public MemObject
{
- public:
- enum Side
+ protected:
+ /** Decleration of the buses port type, one will be instantiated for each
+ of the interfaces connecting to the bus. */
+ class BridgePort : public Port
{
- SideA,
- SideB
- };
+ /** A pointer to the bridge to which this port belongs. */
+ Bridge *bridge;
- protected:
- /** Function called by the port when the bus is recieving a Timing
- transaction.*/
- bool recvTiming(Packet *pkt, Side id);
+ /**
+ * Pointer to the port on the other side of the bridge
+ * (connected to the other bus).
+ */
+ BridgePort *otherPort;
- /** Function called by the port when the bus is recieving a Atomic
- transaction.*/
- Tick recvAtomic(Packet *pkt, Side id);
+ /** Minimum delay though this bridge. */
+ Tick delay;
- /** Function called by the port when the bus is recieving a Functional
- transaction.*/
- void recvFunctional(Packet *pkt, Side id);
+ class PacketBuffer : public Packet::SenderState {
- /** Function called by the port when the bus is recieving a status change.*/
- void recvStatusChange(Port::Status status, Side id);
+ public:
+ Tick ready;
+ Packet *pkt;
+ Packet::SenderState *origSenderState;
+ short origSrc;
+ bool expectResponse;
- /** Process address range request.
- * @param resp addresses that we can respond to
- * @param snoop addresses that we would like to snoop
- * @param id ide of the busport that made the request.
- */
- void addressRanges(AddrRangeList &resp, AddrRangeList &snoop, Side id);
+ PacketBuffer(Packet *_pkt, Tick t)
+ : ready(t), pkt(_pkt),
+ origSenderState(_pkt->senderState), origSrc(_pkt->getSrc()),
+ expectResponse(_pkt->needsResponse())
+ {
+ pkt->senderState = this;
+ }
+ void fixResponse(Packet *pkt)
+ {
+ assert(pkt->senderState == this);
+ pkt->setDest(origSrc);
+ pkt->senderState = origSenderState;
+ }
+ };
- /** Event that the SendEvent calls when it fires. This code must reschedule
- * the send event as required. */
- void timerEvent();
+ /**
+ * Outbound packet queue. Packets are held in this queue for a
+ * specified delay to model the processing delay of the
+ * bridge.
+ */
+ std::list<PacketBuffer*> sendQueue;
- /** Decleration of the buses port type, one will be instantiated for each
- of the interfaces connecting to the bus. */
- class BridgePort : public Port
- {
- /** A pointer to the bus to which this port belongs. */
- Bridge *bridge;
+ int outstandingResponses;
+
+ /** Max queue size for outbound packets */
+ int queueLimit;
+
+ /**
+ * Is this side blocked from accepting outbound packets?
+ */
+ bool queueFull() { return (sendQueue.size() == queueLimit); }
+
+ bool queueForSendTiming(Packet *pkt);
+
+ void finishSend(PacketBuffer *buf);
+
+ /**
+ * Handle send event, scheduled when the packet at the head of
+ * the outbound queue is ready to transmit (for timing
+ * accesses only).
+ */
+ void trySend();
+
+ class SendEvent : public Event
+ {
+ BridgePort *port;
+
+ public:
+ SendEvent(BridgePort *p)
+ : Event(&mainEventQueue), port(p) {}
+
+ virtual void process() { port->trySend(); }
- /** A id to keep track of the intercafe ID this port is connected to. */
- Bridge::Side side;
+ virtual const char *description() { return "bridge send event"; }
+ };
+
+ SendEvent sendEvent;
public:
/** Constructor for the BusPort.*/
- BridgePort(Bridge *_bridge, Side _side)
- : Port(""), bridge(_bridge), side(_side)
- { }
-
- int numQueued() { return outbound.size(); }
+ BridgePort(const std::string &_name,
+ Bridge *_bridge, BridgePort *_otherPort,
+ int _delay, int _queueLimit);
protected:
- /** Data this is waiting to be transmitted. */
- std::list<std::pair<Packet*, Tick> > outbound;
-
- void sendPkt(Packet *pkt);
- void sendPkt(std::pair<Packet*, Tick> p);
- /** When reciving a timing request from the peer port,
+ /** When receiving a timing request from the peer port,
pass it to the bridge. */
- virtual bool recvTiming(Packet *pkt)
- { return bridge->recvTiming(pkt, side); }
+ virtual bool recvTiming(Packet *pkt);
- /** When reciving a retry request from the peer port,
+ /** When receiving a retry request from the peer port,
pass it to the bridge. */
virtual Packet* recvRetry();
- /** When reciving a Atomic requestfrom the peer port,
+ /** When receiving a Atomic requestfrom the peer port,
pass it to the bridge. */
- virtual Tick recvAtomic(Packet *pkt)
- { return bridge->recvAtomic(pkt, side); }
+ virtual Tick recvAtomic(Packet *pkt);
- /** When reciving a Functional request from the peer port,
+ /** When receiving a Functional request from the peer port,
pass it to the bridge. */
- virtual void recvFunctional(Packet *pkt)
- { bridge->recvFunctional(pkt, side); }
+ virtual void recvFunctional(Packet *pkt);
- /** When reciving a status changefrom the peer port,
+ /** When receiving a status changefrom the peer port,
pass it to the bridge. */
- virtual void recvStatusChange(Status status)
- { bridge->recvStatusChange(status, side); }
+ virtual void recvStatusChange(Status status);
- /** When reciving a address range request the peer port,
+ /** When receiving a address range request the peer port,
pass it to the bridge. */
- virtual void getDeviceAddressRanges(AddrRangeList &resp, AddrRangeList &snoop)
- { bridge->addressRanges(resp, snoop, side); }
-
- friend class Bridge;
- };
-
- class SendEvent : public Event
- {
- Bridge *bridge;
-
- SendEvent(Bridge *b)
- : Event(&mainEventQueue), bridge(b) {}
-
- virtual void process() { bridge->timerEvent(); }
-
- virtual const char *description() { return "bridge delay event"; }
- friend class Bridge;
+ virtual void getDeviceAddressRanges(AddrRangeList &resp,
+ AddrRangeList &snoop);
};
- SendEvent sendEvent;
-
- /** Sides of the bus bridges. */
- BridgePort* sideA;
- BridgePort* sideB;
-
- /** inbound queues on both sides. */
- std::list<std::pair<Packet*, Tick> > inboundA;
- std::list<std::pair<Packet*, Tick> > inboundB;
-
- /** The size of the queue for data coming into side a */
- int queueSizeA;
- int queueSizeB;
-
- /* if the side is blocked or not. */
- bool blockedA;
- bool blockedB;
-
- /** Miminum delay though this bridge. */
- Tick delay;
+ BridgePort portA, portB;
/** If this bridge should acknowledge writes. */
bool ackWrites;
public:
/** A function used to return the port associated with this bus object. */
- virtual Port *getPort(const std::string &if_name)
- {
- if (if_name == "side_a") {
- if (sideA != NULL)
- panic("bridge side a already connected to.");
- sideA = new BridgePort(this, SideA);
- return sideA;
- } else if (if_name == "side_b") {
- if (sideB != NULL)
- panic("bridge side b already connected to.");
- sideB = new BridgePort(this, SideB);
- return sideB;
- } else
- return NULL;
- }
+ virtual Port *getPort(const std::string &if_name);
virtual void init();
- Bridge(const std::string &n, int qsa, int qsb, Tick _delay, int write_ack)
- : MemObject(n), sendEvent(this), sideA(NULL), sideB(NULL),
- queueSizeA(qsa), queueSizeB(qsb), blockedA(false), blockedB(false),
- delay(_delay), ackWrites(write_ack)
- {}
-
- /** Check if the port should block/unblock after recieving/sending a packet.
- * */
- void blockCheck(Side id);
-
- friend class Bridge::SendEvent;
-
+ Bridge(const std::string &n, int qsa, int qsb, Tick _delay, int write_ack);
};
#endif //__MEM_BUS_HH__
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