void
Bus::init()
{
- std::vector<Port*>::iterator intIter;
+ std::vector<BusPort*>::iterator intIter;
for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
(*intIter)->sendStatusChange(Port::RangeChange);
}
+Bus::BusFreeEvent::BusFreeEvent(Bus *_bus) : Event(&mainEventQueue), bus(_bus)
+{}
+
+void Bus::BusFreeEvent::process()
+{
+ bus->recvRetry(-1);
+}
+
+const char * Bus::BusFreeEvent::description()
+{
+ return "bus became available";
+}
+
+void Bus::occupyBus(PacketPtr pkt)
+{
+ //Bring tickNextIdle up to the present tick
+ //There is some potential ambiguity where a cycle starts, which might make
+ //a difference when devices are acting right around a cycle boundary. Using
+ //a < allows things which happen exactly on a cycle boundary to take up only
+ //the following cycle. Anthing that happens later will have to "wait" for
+ //the end of that cycle, and then start using the bus after that.
+ while (tickNextIdle < curTick)
+ tickNextIdle += clock;
+
+ // The packet will be sent. Figure out how long it occupies the bus, and
+ // how much of that time is for the first "word", aka bus width.
+ int numCycles = 0;
+ // Requests need one cycle to send an address
+ if (pkt->isRequest())
+ numCycles++;
+ else if (pkt->isResponse() || pkt->hasData()) {
+ // If a packet has data, it needs ceil(size/width) cycles to send it
+ // We're using the "adding instead of dividing" trick again here
+ if (pkt->hasData()) {
+ int dataSize = pkt->getSize();
+ for (int transmitted = 0; transmitted < dataSize;
+ transmitted += width) {
+ numCycles++;
+ }
+ } else {
+ // If the packet didn't have data, it must have been a response.
+ // Those use the bus for one cycle to send their data.
+ numCycles++;
+ }
+ }
+
+ // The first word will be delivered after the current tick, the delivery
+ // of the address if any, and one bus cycle to deliver the data
+ pkt->firstWordTime =
+ tickNextIdle +
+ pkt->isRequest() ? clock : 0 +
+ clock;
+
+ //Advance it numCycles bus cycles.
+ //XXX Should this use the repeated addition trick as well?
+ tickNextIdle += (numCycles * clock);
+ if (!busIdle.scheduled()) {
+ busIdle.schedule(tickNextIdle);
+ } else {
+ busIdle.reschedule(tickNextIdle);
+ }
+ DPRINTF(Bus, "The bus is now occupied from tick %d to %d\n",
+ curTick, tickNextIdle);
+
+ // The bus will become idle once the current packet is delivered.
+ pkt->finishTime = tickNextIdle;
+}
/** Function called by the port when the bus is receiving a Timing
* transaction.*/
DPRINTF(Bus, "recvTiming: packet src %d dest %d addr 0x%x cmd %s\n",
pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
+ BusPort *pktPort = interfaces[pkt->getSrc()];
+
+ // If the bus is busy, or other devices are in line ahead of the current
+ // one, put this device on the retry list.
+ if (tickNextIdle > curTick ||
+ (retryList.size() && (!inRetry || pktPort != retryList.front()))) {
+ addToRetryList(pktPort);
+ return false;
+ }
+
short dest = pkt->getDest();
if (dest == Packet::Broadcast) {
- if (timingSnoop(pkt))
- {
+ if (timingSnoop(pkt)) {
pkt->flags |= SNOOP_COMMIT;
bool success = timingSnoop(pkt);
assert(success);
if (pkt->flags & SATISFIED) {
//Cache-Cache transfer occuring
+ if (inRetry) {
+ retryList.front()->onRetryList(false);
+ retryList.pop_front();
+ inRetry = false;
+ }
+ occupyBus(pkt);
return true;
}
port = findPort(pkt->getAddr(), pkt->getSrc());
- }
- else
- {
+ } else {
//Snoop didn't succeed
- retryList.push_back(interfaces[pkt->getSrc()]);
+ addToRetryList(pktPort);
return false;
}
} else {
assert(dest != pkt->getSrc()); // catch infinite loops
port = interfaces[dest];
}
+
+ occupyBus(pkt);
+
if (port->sendTiming(pkt)) {
- // packet was successfully sent, just return true.
+ // Packet was successfully sent. Return true.
+ // Also take care of retries
+ if (inRetry) {
+ DPRINTF(Bus, "Remove retry from list %i\n", retryList.front());
+ retryList.front()->onRetryList(false);
+ retryList.pop_front();
+ inRetry = false;
+ }
return true;
}
- // packet not successfully sent
- retryList.push_back(interfaces[pkt->getSrc()]);
+ // Packet not successfully sent. Leave or put it on the retry list.
+ DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
+ addToRetryList(pktPort);
return false;
}
void
Bus::recvRetry(int id)
{
- // Go through all the elements on the list calling sendRetry on each
- // This is not very efficient at all but it works. Ultimately we should end
- // up with something that is more intelligent.
- int initialSize = retryList.size();
- int i;
- Port *p;
-
- for (i = 0; i < initialSize; i++) {
- assert(retryList.size() > 0);
- p = retryList.front();
- retryList.pop_front();
- p->sendRetry();
+ DPRINTF(Bus, "Received a retry\n");
+ // If there's anything waiting...
+ if (retryList.size()) {
+ //retryingPort = retryList.front();
+ inRetry = true;
+ DPRINTF(Bus, "Sending a retry\n");
+ retryList.front()->sendRetry();
+ // If inRetry is still true, sendTiming wasn't called
+ if (inRetry)
+ panic("Port %s didn't call sendTiming in it's recvRetry\n",\
+ retryList.front()->getPeer()->name());
+ //assert(!inRetry);
}
}
-
Port *
Bus::findPort(Addr addr, int id)
{
//Careful to not overlap ranges
//or snoop will be called more than once on the port
ports.push_back(portSnoopList[i].portId);
- DPRINTF(Bus, " found snoop addr %#llx on device%d\n", addr,
- portSnoopList[i].portId);
+// DPRINTF(Bus, " found snoop addr %#llx on device%d\n", addr,
+// portSnoopList[i].portId);
}
i++;
}
BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
Param<int> bus_id;
+ Param<int> clock;
+ Param<int> width;
END_DECLARE_SIM_OBJECT_PARAMS(Bus)
BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
- INIT_PARAM(bus_id, "a globally unique bus id")
+ INIT_PARAM(bus_id, "a globally unique bus id"),
+ INIT_PARAM(clock, "bus clock speed"),
+ INIT_PARAM(width, "width of the bus (bits)")
END_INIT_SIM_OBJECT_PARAMS(Bus)
CREATE_SIM_OBJECT(Bus)
{
- return new Bus(getInstanceName(), bus_id);
+ return new Bus(getInstanceName(), bus_id, clock, width);
}
REGISTER_SIM_OBJECT("Bus", Bus)
projects / gem5.git / blobdiff