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-rw-r--r--src/mem/bus.cc315
-rw-r--r--src/mem/bus.hh30
2 files changed, 198 insertions, 147 deletions
diff --git a/src/mem/bus.cc b/src/mem/bus.cc
index 827adc78e..0c0e3c3e2 100644
--- a/src/mem/bus.cc
+++ b/src/mem/bus.cc
@@ -50,13 +50,12 @@
#include "base/trace.hh"
#include "debug/Bus.hh"
#include "debug/BusAddrRanges.hh"
-#include "debug/MMU.hh"
#include "mem/bus.hh"
Bus::Bus(const BusParams *p)
- : MemObject(p), busId(p->bus_id), clock(p->clock),
+ : MemObject(p), clock(p->clock),
headerCycles(p->header_cycles), width(p->width), tickNextIdle(0),
- drainEvent(NULL), busIdle(this), inRetry(false),
+ drainEvent(NULL), busIdleEvent(this), inRetry(false),
nbrMasterPorts(p->port_master_connection_count),
defaultPortId(INVALID_PORT_ID), useDefaultRange(p->use_default_range),
defaultBlockSize(p->block_size),
@@ -82,21 +81,23 @@ Bus::Bus(const BusParams *p)
++id;
}
- // note that the first slave port is now stored on index
- // nbrMasterPorts in the vector
- for (int i = 0; i < p->port_slave_connection_count; ++i) {
- std::string portName = csprintf("%s-p%d", name(), id);
- interfaces.push_back(new BusPort(portName, this, id));
- ++id;
- }
-
// see if we have a default master connected and if so add the
- // port at the end
+ // port
if (p->port_default_connection_count) {
defaultPortId = id;
std::string portName = csprintf("%s-default", name());
interfaces.push_back(new BusPort(portName, this, id));
++id;
+ // this is an additional master port
+ ++nbrMasterPorts;
+ }
+
+ // note that the first slave port is now stored on index
+ // nbrMasterPorts in the vector
+ for (int i = 0; i < p->port_slave_connection_count; ++i) {
+ std::string portName = csprintf("%s-p%d", name(), id);
+ interfaces.push_back(new BusPort(portName, this, id));
+ ++id;
}
clearPortCache();
@@ -137,39 +138,17 @@ Bus::init()
}
}
-Bus::BusFreeEvent::BusFreeEvent(Bus *_bus)
- : bus(_bus)
-{}
-
-void
-Bus::BusFreeEvent::process()
-{
- bus->recvRetry(-1);
-}
-
-const char *
-Bus::BusFreeEvent::description() const
-{
- return "bus became available";
-}
-
Tick
Bus::calcPacketTiming(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. Anything
- // that happens later will have to "wait" for the end of that
- // cycle, and then start using the bus after that.
- if (tickNextIdle < curTick()) {
- tickNextIdle = curTick();
- if (tickNextIdle % clock != 0)
- tickNextIdle = curTick() - (curTick() % clock) + clock;
+ // determine the current time rounded to the closest following
+ // clock edge
+ Tick now = curTick();
+ if (now % clock != 0) {
+ now = ((now / clock) + 1) * clock;
}
- Tick headerTime = tickNextIdle + headerCycles * clock;
+ Tick headerTime = now + headerCycles * 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.
@@ -199,7 +178,7 @@ void Bus::occupyBus(Tick until)
}
tickNextIdle = until;
- reschedule(busIdle, tickNextIdle, true);
+ reschedule(busIdleEvent, tickNextIdle, true);
DPRINTF(Bus, "The bus is now occupied from tick %d to %d\n",
curTick(), tickNextIdle);
@@ -210,55 +189,72 @@ void Bus::occupyBus(Tick until)
bool
Bus::recvTiming(PacketPtr pkt)
{
- short src = pkt->getSrc();
+ // called for both requests and responses
- BusPort *src_port = interfaces[src];
+ // get the source id and port
+ Packet::NodeID src_id = pkt->getSrc();
+
+ BusPort *src_port = interfaces[src_id];
// If the bus is busy, or other devices are in line ahead of the current
// one, put this device on the retry list.
if (!pkt->isExpressSnoop() &&
(tickNextIdle > curTick() ||
- (retryList.size() && (!inRetry || src_port != retryList.front()))))
+ (!retryList.empty() && (!inRetry || src_port != retryList.front()))))
{
addToRetryList(src_port);
DPRINTF(Bus, "recvTiming: src %d dst %d %s 0x%x BUSY\n",
- src, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+ src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
return false;
}
DPRINTF(Bus, "recvTiming: src %d dst %d %s 0x%x\n",
- src, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+ src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
Tick headerFinishTime = pkt->isExpressSnoop() ? 0 : calcPacketTiming(pkt);
Tick packetFinishTime = pkt->isExpressSnoop() ? 0 : pkt->finishTime;
- short dest = pkt->getDest();
- int dest_port_id;
+ Packet::NodeID dest = pkt->getDest();
+ int dest_id;
Port *dest_port;
if (dest == Packet::Broadcast) {
- dest_port_id = findPort(pkt->getAddr());
- dest_port = interfaces[dest_port_id];
+ // the packet is a memory-mapped request and should be broadcasted to
+ // our snoopers
+ assert(pkt->isRequest());
+
SnoopIter s_end = snoopPorts.end();
for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
BusPort *p = *s_iter;
- if (p != dest_port && p != src_port) {
+ // we got this request from a snooping master
+ // (corresponding to our own slave port that is also in
+ // snoopPorts) and should not send it back to where it
+ // came from
+ if (p->getId() != src_id) {
// cache is not allowed to refuse snoop
bool success M5_VAR_USED = p->sendTiming(pkt);
assert(success);
}
}
+
+ // since it is a request, similar to functional and atomic,
+ // determine the destination based on the address and forward
+ // through the corresponding master port
+ dest_id = findPort(pkt->getAddr());
+ dest_port = interfaces[dest_id];
} else {
- assert(dest < interfaces.size());
- assert(dest != src); // catch infinite loops
- dest_port_id = dest;
- dest_port = interfaces[dest_port_id];
+ // the packet is a response, and it should always go back to
+ // the port determined by the destination field
+ dest_id = dest;
+ assert(dest_id != src_id); // catch infinite loops
+ assert(dest_id < interfaces.size());
+ dest_port = interfaces[dest_id];
}
- if (dest_port_id == src) {
- // Must be forwarded snoop up from below...
- assert(dest == Packet::Broadcast);
- } else {
+ // if this is a snoop from a slave (corresponding to our own
+ // master), i.e. the memory side of the bus, then do not send it
+ // back to where it came from
+ if (dest_id != src_id) {
// send to actual target
if (!dest_port->sendTiming(pkt)) {
// Packet not successfully sent. Leave or put it on the retry list.
@@ -268,7 +264,7 @@ Bus::recvTiming(PacketPtr pkt)
// someone else has committed to respond.
assert(!pkt->memInhibitAsserted());
DPRINTF(Bus, "recvTiming: src %d dst %d %s 0x%x TGT RETRY\n",
- src, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+ src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
addToRetryList(src_port);
occupyBus(headerFinishTime);
return false;
@@ -284,7 +280,7 @@ Bus::recvTiming(PacketPtr pkt)
// Packet was successfully sent.
// Also take care of retries
if (inRetry) {
- DPRINTF(Bus, "Remove retry from list %d\n", src);
+ DPRINTF(Bus, "Remove retry from list %d\n", src_id);
retryList.pop_front();
inRetry = false;
}
@@ -292,38 +288,81 @@ Bus::recvTiming(PacketPtr pkt)
}
void
-Bus::recvRetry(int id)
+Bus::releaseBus()
{
- // If there's anything waiting, and the bus isn't busy...
- if (retryList.size() && curTick() >= tickNextIdle) {
- //retryingPort = retryList.front();
- inRetry = true;
- DPRINTF(Bus, "Sending a retry to %s\n", retryList.front()->getPeer()->name());
- retryList.front()->sendRetry();
- // If inRetry is still true, sendTiming wasn't called
- if (inRetry)
- {
- retryList.pop_front();
- inRetry = false;
-
- //Bring tickNextIdle up to the present
- while (tickNextIdle < curTick())
- tickNextIdle += clock;
-
- //Burn a cycle for the missed grant.
- tickNextIdle += clock;
-
- reschedule(busIdle, tickNextIdle, true);
- }
+ // releasing the bus means we should now be idle
+ assert(curTick() >= tickNextIdle);
+
+ // bus is now idle, so if someone is waiting we can retry
+ if (!retryList.empty()) {
+ // note that we block (return false on recvTiming) both
+ // because the bus is busy and because the destination is
+ // busy, and in the latter case the bus may be released before
+ // we see a retry from the destination
+ retryWaiting();
}
+
//If we weren't able to drain before, we might be able to now.
- if (drainEvent && retryList.size() == 0 && curTick() >= tickNextIdle) {
+ if (drainEvent && retryList.empty() && curTick() >= tickNextIdle) {
drainEvent->process();
// Clear the drain event once we're done with it.
drainEvent = NULL;
}
}
+void
+Bus::retryWaiting()
+{
+ // this should never be called with an empty retry list
+ assert(!retryList.empty());
+
+ // send a retry to the port at the head of the retry list
+ inRetry = true;
+ DPRINTF(Bus, "Sending a retry to %s\n",
+ retryList.front()->getPeer()->name());
+
+ // note that we might have blocked on the receiving port being
+ // busy (rather than the bus itself) and now call retry before the
+ // destination called retry on the bus
+ retryList.front()->sendRetry();
+
+ // If inRetry is still true, sendTiming wasn't called in zero time
+ // (e.g. the cache does this)
+ if (inRetry) {
+ retryList.pop_front();
+ inRetry = false;
+
+ //Bring tickNextIdle up to the present
+ while (tickNextIdle < curTick())
+ tickNextIdle += clock;
+
+ //Burn a cycle for the missed grant.
+ tickNextIdle += clock;
+
+ reschedule(busIdleEvent, tickNextIdle, true);
+ }
+}
+
+void
+Bus::recvRetry(int id)
+{
+ // we got a retry from a peer that we tried to send something to
+ // and failed, but we sent it on the account of someone else, and
+ // that source port should be on our retry list, however if the
+ // bus is released before this happens and the retry (from the bus
+ // point of view) is successful then this no longer holds and we
+ // could in fact have an empty retry list
+ if (retryList.empty())
+ return;
+
+ // if the bus isn't busy
+ if (curTick() >= tickNextIdle) {
+ // note that we do not care who told us to retry at the moment, we
+ // merely let the first one on the retry list go
+ retryWaiting();
+ }
+}
+
int
Bus::findPort(Addr addr)
{
@@ -371,28 +410,33 @@ Bus::recvAtomic(PacketPtr pkt)
{
DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
+
+ // we should always see a request routed based on the address
assert(pkt->getDest() == Packet::Broadcast);
assert(pkt->isRequest());
- // Variables for recording original command and snoop response (if
- // any)... if a snooper respondes, we will need to restore
- // original command so that additional snoops can take place
- // properly
+ // the packet may be changed by another bus on snoops, record the
+ // source id here
+ Packet::NodeID src_id = pkt->getSrc();
+
+ // record the original command to enable us to restore it between
+ // snoops so that additional snoops can take place properly
MemCmd orig_cmd = pkt->cmd;
MemCmd snoop_response_cmd = MemCmd::InvalidCmd;
Tick snoop_response_latency = 0;
- int orig_src = pkt->getSrc();
-
- int target_port_id = findPort(pkt->getAddr());
- BusPort *target_port = interfaces[target_port_id];
SnoopIter s_end = snoopPorts.end();
for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
BusPort *p = *s_iter;
- // same port should not have both target addresses and snooping
- assert(p != target_port);
- if (p->getId() != pkt->getSrc()) {
+ // we could have gotten this request from a snooping master
+ // (corresponding to our own slave port that is also in
+ // snoopPorts) and should not send it back to where it came
+ // from
+ if (p->getId() != src_id) {
Tick latency = p->sendAtomic(pkt);
+ // in contrast to a functional access, we have to keep on
+ // going as all snoopers must be updated even if we get a
+ // response
if (pkt->isResponse()) {
// response from snoop agent
assert(pkt->cmd != orig_cmd);
@@ -404,18 +448,23 @@ Bus::recvAtomic(PacketPtr pkt)
snoop_response_latency = latency;
// restore original packet state for remaining snoopers
pkt->cmd = orig_cmd;
- pkt->setSrc(orig_src);
+ pkt->setSrc(src_id);
pkt->setDest(Packet::Broadcast);
}
}
}
+ // even if we had a snoop response, we must continue and also
+ // perform the actual request at the destination
+ int dest_id = findPort(pkt->getAddr());
+
Tick response_latency = 0;
- // we can get requests sent up from the memory side of the bus for
- // snooping... don't send them back down!
- if (target_port_id != pkt->getSrc()) {
- response_latency = target_port->sendAtomic(pkt);
+ // if this is a snoop from a slave (corresponding to our own
+ // master), i.e. the memory side of the bus, then do not send it
+ // back to where it came from
+ if (dest_id != src_id) {
+ response_latency = interfaces[dest_id]->sendAtomic(pkt);
}
// if we got a response from a snooper, restore it here
@@ -437,40 +486,50 @@ Bus::recvAtomic(PacketPtr pkt)
void
Bus::recvFunctional(PacketPtr pkt)
{
- assert(pkt->getDest() == Packet::Broadcast);
-
- int port_id = findPort(pkt->getAddr());
- Port *port = interfaces[port_id];
- // The packet may be changed by another bus on snoops, restore the
- // id after each
- int src_id = pkt->getSrc();
-
if (!pkt->isPrint()) {
// don't do DPRINTFs on PrintReq as it clutters up the output
DPRINTF(Bus,
"recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
- src_id, port_id, pkt->getAddr(),
+ pkt->getSrc(), pkt->getDest(), pkt->getAddr(),
pkt->cmdString());
}
- assert(pkt->isRequest()); // hasn't already been satisfied
+ // we should always see a request routed based on the address
+ assert(pkt->getDest() == Packet::Broadcast);
+ assert(pkt->isRequest());
+
+ // the packet may be changed by another bus on snoops, record the
+ // source id here
+ Packet::NodeID src_id = pkt->getSrc();
SnoopIter s_end = snoopPorts.end();
for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
BusPort *p = *s_iter;
- if (p != port && p->getId() != src_id) {
+ // we could have gotten this request from a snooping master
+ // (corresponding to our own slave port that is also in
+ // snoopPorts) and should not send it back to where it came
+ // from
+ if (p->getId() != src_id) {
p->sendFunctional(pkt);
+
+ // if we get a response we are done
+ if (pkt->isResponse()) {
+ break;
+ }
}
- if (pkt->isResponse()) {
- break;
- }
- pkt->setSrc(src_id);
}
- // If the snooping hasn't found what we were looking for and it is not
- // a forwarded snoop from below, keep going.
- if (!pkt->isResponse() && port_id != pkt->getSrc()) {
- port->sendFunctional(pkt);
+ // there is no need to continue if the snooping has found what we
+ // were looking for and the packet is already a response
+ if (!pkt->isResponse()) {
+ int dest_id = findPort(pkt->getAddr());
+
+ // if this is a snoop from a slave (corresponding to our own
+ // master), i.e. the memory side of the bus, then do not send
+ // it back to where it came from,
+ if (dest_id != src_id) {
+ interfaces[dest_id]->sendFunctional(pkt);
+ }
}
}
@@ -526,7 +585,7 @@ Bus::recvRangeChange(int id)
}
}
}
- DPRINTF(MMU, "port list has %d entries\n", portMap.size());
+ DPRINTF(BusAddrRanges, "port list has %d entries\n", portMap.size());
// tell all our peers that our address range has changed.
// Don't tell the device that caused this change, it already knows
@@ -583,17 +642,8 @@ Bus::getAddrRanges(int id)
bool
Bus::isSnooping(int id)
{
- // in essence, answer the question if there are other snooping
- // ports rather than the port that is asking
- bool snoop = false;
- for (SnoopIter s_iter = snoopPorts.begin(); s_iter != snoopPorts.end();
- s_iter++) {
- if ((*s_iter)->getId() != id) {
- snoop = true;
- break;
- }
- }
- return snoop;
+ // in essence, answer the question if there are snooping ports
+ return !snoopPorts.empty();
}
unsigned
@@ -633,7 +683,8 @@ Bus::drain(Event * de)
//We should check that we're not "doing" anything, and that noone is
//waiting. We might be idle but have someone waiting if the device we
//contacted for a retry didn't actually retry.
- if (retryList.size() || (curTick() < tickNextIdle && busIdle.scheduled())) {
+ if (!retryList.empty() || (curTick() < tickNextIdle &&
+ busIdleEvent.scheduled())) {
drainEvent = de;
return 1;
}
diff --git a/src/mem/bus.hh b/src/mem/bus.hh
index 7fdf5db26..4ea92308a 100644
--- a/src/mem/bus.hh
+++ b/src/mem/bus.hh
@@ -54,14 +54,12 @@
#include <set>
#include <string>
-#include "base/hashmap.hh"
#include "base/range.hh"
#include "base/range_map.hh"
#include "base/types.hh"
#include "mem/mem_object.hh"
#include "mem/packet.hh"
#include "mem/port.hh"
-#include "mem/request.hh"
#include "params/Bus.hh"
#include "sim/eventq.hh"
@@ -137,18 +135,6 @@ class Bus : public MemObject
};
- class BusFreeEvent : public Event
- {
- Bus * bus;
-
- public:
- BusFreeEvent(Bus * _bus);
- void process();
- const char *description() const;
- };
-
- /** a globally unique id for this bus. */
- int busId;
/** the clock speed for the bus */
int clock;
/** cycles of overhead per transaction */
@@ -276,13 +262,27 @@ class Bus : public MemObject
/** Occupy the bus until until */
void occupyBus(Tick until);
+ /**
+ * Release the bus after being occupied and return to an idle
+ * state where we proceed to send a retry to any potential waiting
+ * port, or drain if asked to do so.
+ */
+ void releaseBus();
+
+ /**
+ * Send a retry to the port at the head of the retryList. The
+ * caller must ensure that the list is not empty.
+ */
+ void retryWaiting();
+
/** Ask everyone on the bus what their size is
* @param id id of the busport that made the request
* @return the max of all the sizes
*/
unsigned findBlockSize(int id);
- BusFreeEvent busIdle;
+ // event used to schedule a release of the bus
+ EventWrapper<Bus, &Bus::releaseBus> busIdleEvent;
bool inRetry;
std::set<int> inRecvRangeChange;
generated by cgit v1.2.3 (git 2.25.1) at 2024-10-30 08:43:06 +0000