mem: Rename Bus to XBar to better reflect its behaviour

This patch changes the name of the Bus classes to XBar to better
reflect the actual timing behaviour. The actual instances in the
config scripts are not renamed, and remain as e.g. iobus or membus.

As part of this renaming, the code has also been clean up slightly,
making use of range-based for loops and tidying up some comments. The
only changes outside the bus/crossbar code is due to the delay
variables in the packet.

--HG--
rename : src/mem/Bus.py => src/mem/XBar.py
rename : src/mem/coherent_bus.cc => src/mem/coherent_xbar.cc
rename : src/mem/coherent_bus.hh => src/mem/coherent_xbar.hh
rename : src/mem/noncoherent_bus.cc => src/mem/noncoherent_xbar.cc
rename : src/mem/noncoherent_bus.hh => src/mem/noncoherent_xbar.hh
rename : src/mem/bus.cc => src/mem/xbar.cc
rename : src/mem/bus.hh => src/mem/xbar.hh

1 files changed, 614 insertions, 0 deletions

diff --git a/src/mem/xbar.cc b/src/mem/xbar.cc
new file mode 100644
index 000000000..6e4630fb6
--- /dev/null
+++ b/src/mem/xbar.cc
@@ -0,0 +1,614 @@
+/*
+ * Copyright (c) 2011-2014 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Copyright (c) 2006 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Ali Saidi
+ *          Andreas Hansson
+ *          William Wang
+ */
+
+/**
+ * @file
+ * Definition of a crossbar object.
+ */
+
+#include "base/misc.hh"
+#include "base/trace.hh"
+#include "debug/AddrRanges.hh"
+#include "debug/Drain.hh"
+#include "debug/XBar.hh"
+#include "mem/xbar.hh"
+
+BaseXBar::BaseXBar(const BaseXBarParams *p)
+    : MemObject(p),
+      headerCycles(p->header_cycles), width(p->width),
+      gotAddrRanges(p->port_default_connection_count +
+                          p->port_master_connection_count, false),
+      gotAllAddrRanges(false), defaultPortID(InvalidPortID),
+      useDefaultRange(p->use_default_range)
+{}
+
+BaseXBar::~BaseXBar()
+{
+    for (auto m: masterPorts)
+        delete m;
+
+    for (auto s: slavePorts)
+        delete s;
+}
+
+void
+BaseXBar::init()
+{
+}
+
+BaseMasterPort &
+BaseXBar::getMasterPort(const std::string &if_name, PortID idx)
+{
+    if (if_name == "master" && idx < masterPorts.size()) {
+        // the master port index translates directly to the vector position
+        return *masterPorts[idx];
+    } else  if (if_name == "default") {
+        return *masterPorts[defaultPortID];
+    } else {
+        return MemObject::getMasterPort(if_name, idx);
+    }
+}
+
+BaseSlavePort &
+BaseXBar::getSlavePort(const std::string &if_name, PortID idx)
+{
+    if (if_name == "slave" && idx < slavePorts.size()) {
+        // the slave port index translates directly to the vector position
+        return *slavePorts[idx];
+    } else {
+        return MemObject::getSlavePort(if_name, idx);
+    }
+}
+
+void
+BaseXBar::calcPacketTiming(PacketPtr pkt)
+{
+    // the crossbar will be called at a time that is not necessarily
+    // coinciding with its own clock, so start by determining how long
+    // until the next clock edge (could be zero)
+    Tick offset = clockEdge() - curTick();
+
+    // determine how many cycles are needed to send the data
+    unsigned dataCycles = pkt->hasData() ? divCeil(pkt->getSize(), width) : 0;
+
+    // before setting the bus delay fields of the packet, ensure that
+    // the delay from any previous crossbar has been accounted for
+    if (pkt->firstWordDelay != 0 || pkt->lastWordDelay != 0)
+        panic("Packet %s already has delay (%d, %d) that should be "
+              "accounted for.\n", pkt->cmdString(), pkt->firstWordDelay,
+              pkt->lastWordDelay);
+
+    // The first word will be delivered on the cycle after the header.
+    pkt->firstWordDelay = (headerCycles + 1) * clockPeriod() + offset;
+
+    // Note that currently lastWordDelay can be smaller than
+    // firstWordDelay if the packet has no data
+    pkt->lastWordDelay = (headerCycles + dataCycles) * clockPeriod() +
+        offset;
+}
+
+template <typename SrcType, typename DstType>
+BaseXBar::Layer<SrcType,DstType>::Layer(DstType& _port, BaseXBar& _xbar,
+                                       const std::string& _name) :
+    port(_port), xbar(_xbar), _name(_name), state(IDLE), drainManager(NULL),
+    waitingForPeer(NULL), releaseEvent(this)
+{
+}
+
+template <typename SrcType, typename DstType>
+void BaseXBar::Layer<SrcType,DstType>::occupyLayer(Tick until)
+{
+    // ensure the state is busy at this point, as the layer should
+    // transition from idle as soon as it has decided to forward the
+    // packet to prevent any follow-on calls to sendTiming seeing an
+    // unoccupied layer
+    assert(state == BUSY);
+
+    // until should never be 0 as express snoops never occupy the layer
+    assert(until != 0);
+    xbar.schedule(releaseEvent, until);
+
+    // account for the occupied ticks
+    occupancy += until - curTick();
+
+    DPRINTF(BaseXBar, "The crossbar layer is now busy from tick %d to %d\n",
+            curTick(), until);
+}
+
+template <typename SrcType, typename DstType>
+bool
+BaseXBar::Layer<SrcType,DstType>::tryTiming(SrcType* src_port)
+{
+    // if we are in the retry state, we will not see anything but the
+    // retrying port (or in the case of the snoop ports the snoop
+    // response port that mirrors the actual slave port) as we leave
+    // this state again in zero time if the peer does not immediately
+    // call the layer when receiving the retry
+
+    // first we see if the layer is busy, next we check if the
+    // destination port is already engaged in a transaction waiting
+    // for a retry from the peer
+    if (state == BUSY || waitingForPeer != NULL) {
+        // the port should not be waiting already
+        assert(std::find(waitingForLayer.begin(), waitingForLayer.end(),
+                         src_port) == waitingForLayer.end());
+
+        // put the port at the end of the retry list waiting for the
+        // layer to be freed up (and in the case of a busy peer, for
+        // that transaction to go through, and then the layer to free
+        // up)
+        waitingForLayer.push_back(src_port);
+        return false;
+    }
+
+    state = BUSY;
+
+    return true;
+}
+
+template <typename SrcType, typename DstType>
+void
+BaseXBar::Layer<SrcType,DstType>::succeededTiming(Tick busy_time)
+{
+    // we should have gone from idle or retry to busy in the tryTiming
+    // test
+    assert(state == BUSY);
+
+    // occupy the layer accordingly
+    occupyLayer(busy_time);
+}
+
+template <typename SrcType, typename DstType>
+void
+BaseXBar::Layer<SrcType,DstType>::failedTiming(SrcType* src_port,
+                                              Tick busy_time)
+{
+    // ensure no one got in between and tried to send something to
+    // this port
+    assert(waitingForPeer == NULL);
+
+    // if the source port is the current retrying one or not, we have
+    // failed in forwarding and should track that we are now waiting
+    // for the peer to send a retry
+    waitingForPeer = src_port;
+
+    // we should have gone from idle or retry to busy in the tryTiming
+    // test
+    assert(state == BUSY);
+
+    // occupy the bus accordingly
+    occupyLayer(busy_time);
+}
+
+template <typename SrcType, typename DstType>
+void
+BaseXBar::Layer<SrcType,DstType>::releaseLayer()
+{
+    // releasing the bus means we should now be idle
+    assert(state == BUSY);
+    assert(!releaseEvent.scheduled());
+
+    // update the state
+    state = IDLE;
+
+    // bus layer is now idle, so if someone is waiting we can retry
+    if (!waitingForLayer.empty()) {
+        // there is no point in sending a retry if someone is still
+        // waiting for the peer
+        if (waitingForPeer == NULL)
+            retryWaiting();
+    } else if (waitingForPeer == NULL && drainManager) {
+        DPRINTF(Drain, "Crossbar done draining, signaling drain manager\n");
+        //If we weren't able to drain before, do it now.
+        drainManager->signalDrainDone();
+        // Clear the drain event once we're done with it.
+        drainManager = NULL;
+    }
+}
+
+template <typename SrcType, typename DstType>
+void
+BaseXBar::Layer<SrcType,DstType>::retryWaiting()
+{
+    // this should never be called with no one waiting
+    assert(!waitingForLayer.empty());
+
+    // we always go to retrying from idle
+    assert(state == IDLE);
+
+    // update the state
+    state = RETRY;
+
+    // set the retrying port to the front of the retry list and pop it
+    // off the list
+    SrcType* retryingPort = waitingForLayer.front();
+    waitingForLayer.pop_front();
+
+    // tell the port to retry, which in some cases ends up calling the
+    // layer again
+    retryingPort->sendRetry();
+
+    // If the layer is still in the retry state, sendTiming wasn't
+    // called in zero time (e.g. the cache does this), burn a cycle
+    if (state == RETRY) {
+        // update the state to busy and reset the retrying port, we
+        // have done our bit and sent the retry
+        state = BUSY;
+
+        // occupy the crossbar layer until the next cycle ends
+        occupyLayer(xbar.clockEdge(Cycles(1)));
+    }
+}
+
+template <typename SrcType, typename DstType>
+void
+BaseXBar::Layer<SrcType,DstType>::recvRetry()
+{
+    // we should never get a retry without having failed to forward
+    // something to this port
+    assert(waitingForPeer != NULL);
+
+    // add the port where the failed packet originated to the front of
+    // the waiting ports for the layer, this allows us to call retry
+    // on the port immediately if the crossbar layer is idle
+    waitingForLayer.push_front(waitingForPeer);
+
+    // we are no longer waiting for the peer
+    waitingForPeer = NULL;
+
+    // if the layer is idle, retry this port straight away, if we
+    // are busy, then simply let the port wait for its turn
+    if (state == IDLE) {
+        retryWaiting();
+    } else {
+        assert(state == BUSY);
+    }
+}
+
+PortID
+BaseXBar::findPort(Addr addr)
+{
+    // we should never see any address lookups before we've got the
+    // ranges of all connected slave modules
+    assert(gotAllAddrRanges);
+
+    // Check the cache
+    PortID dest_id = checkPortCache(addr);
+    if (dest_id != InvalidPortID)
+        return dest_id;
+
+    // Check the address map interval tree
+    auto i = portMap.find(addr);
+    if (i != portMap.end()) {
+        dest_id = i->second;
+        updatePortCache(dest_id, i->first);
+        return dest_id;
+    }
+
+    // Check if this matches the default range
+    if (useDefaultRange) {
+        if (defaultRange.contains(addr)) {
+            DPRINTF(AddrRanges, "  found addr %#llx on default\n",
+                    addr);
+            return defaultPortID;
+        }
+    } else if (defaultPortID != InvalidPortID) {
+        DPRINTF(AddrRanges, "Unable to find destination for addr %#llx, "
+                "will use default port\n", addr);
+        return defaultPortID;
+    }
+
+    // we should use the range for the default port and it did not
+    // match, or the default port is not set
+    fatal("Unable to find destination for addr %#llx on %s\n", addr,
+          name());
+}
+
+/** Function called by the port when the crossbar is receiving a range change.*/
+void
+BaseXBar::recvRangeChange(PortID master_port_id)
+{
+    DPRINTF(AddrRanges, "Received range change from slave port %s\n",
+            masterPorts[master_port_id]->getSlavePort().name());
+
+    // remember that we got a range from this master port and thus the
+    // connected slave module
+    gotAddrRanges[master_port_id] = true;
+
+    // update the global flag
+    if (!gotAllAddrRanges) {
+        // take a logical AND of all the ports and see if we got
+        // ranges from everyone
+        gotAllAddrRanges = true;
+        std::vector<bool>::const_iterator r = gotAddrRanges.begin();
+        while (gotAllAddrRanges &&  r != gotAddrRanges.end()) {
+            gotAllAddrRanges &= *r++;
+        }
+        if (gotAllAddrRanges)
+            DPRINTF(AddrRanges, "Got address ranges from all slaves\n");
+    }
+
+    // note that we could get the range from the default port at any
+    // point in time, and we cannot assume that the default range is
+    // set before the other ones are, so we do additional checks once
+    // all ranges are provided
+    if (master_port_id == defaultPortID) {
+        // only update if we are indeed checking ranges for the
+        // default port since the port might not have a valid range
+        // otherwise
+        if (useDefaultRange) {
+            AddrRangeList ranges = masterPorts[master_port_id]->getAddrRanges();
+
+            if (ranges.size() != 1)
+                fatal("Crossbar %s may only have a single default range",
+                      name());
+
+            defaultRange = ranges.front();
+        }
+    } else {
+        // the ports are allowed to update their address ranges
+        // dynamically, so remove any existing entries
+        if (gotAddrRanges[master_port_id]) {
+            for (auto p = portMap.begin(); p != portMap.end(); ) {
+                if (p->second == master_port_id)
+                    // erasing invalidates the iterator, so advance it
+                    // before the deletion takes place
+                    portMap.erase(p++);
+                else
+                    p++;
+            }
+        }
+
+        AddrRangeList ranges = masterPorts[master_port_id]->getAddrRanges();
+
+        for (const auto& r: ranges) {
+            DPRINTF(AddrRanges, "Adding range %s for id %d\n",
+                    r.to_string(), master_port_id);
+            if (portMap.insert(r, master_port_id) == portMap.end()) {
+                PortID conflict_id = portMap.find(r)->second;
+                fatal("%s has two ports with same range:\n\t%s\n\t%s\n",
+                      name(),
+                      masterPorts[master_port_id]->getSlavePort().name(),
+                      masterPorts[conflict_id]->getSlavePort().name());
+            }
+        }
+    }
+
+    // if we have received ranges from all our neighbouring slave
+    // modules, go ahead and tell our connected master modules in
+    // turn, this effectively assumes a tree structure of the system
+    if (gotAllAddrRanges) {
+        DPRINTF(AddrRanges, "Aggregating address ranges\n");
+        xbarRanges.clear();
+
+        // start out with the default range
+        if (useDefaultRange) {
+            if (!gotAddrRanges[defaultPortID])
+                fatal("Crossbar %s uses default range, but none provided",
+                      name());
+
+            xbarRanges.push_back(defaultRange);
+            DPRINTF(AddrRanges, "-- Adding default %s\n",
+                    defaultRange.to_string());
+        }
+
+        // merge all interleaved ranges and add any range that is not
+        // a subset of the default range
+        std::vector<AddrRange> intlv_ranges;
+        for (const auto& r: portMap) {
+            // if the range is interleaved then save it for now
+            if (r.first.interleaved()) {
+                // if we already got interleaved ranges that are not
+                // part of the same range, then first do a merge
+                // before we add the new one
+                if (!intlv_ranges.empty() &&
+                    !intlv_ranges.back().mergesWith(r.first)) {
+                    DPRINTF(AddrRanges, "-- Merging range from %d ranges\n",
+                            intlv_ranges.size());
+                    AddrRange merged_range(intlv_ranges);
+                    // next decide if we keep the merged range or not
+                    if (!(useDefaultRange &&
+                          merged_range.isSubset(defaultRange))) {
+                        xbarRanges.push_back(merged_range);
+                        DPRINTF(AddrRanges, "-- Adding merged range %s\n",
+                                merged_range.to_string());
+                    }
+                    intlv_ranges.clear();
+                }
+                intlv_ranges.push_back(r.first);
+            } else {
+                // keep the current range if not a subset of the default
+                if (!(useDefaultRange &&
+                      r.first.isSubset(defaultRange))) {
+                    xbarRanges.push_back(r.first);
+                    DPRINTF(AddrRanges, "-- Adding range %s\n",
+                            r.first.to_string());
+                }
+            }
+        }
+
+        // if there is still interleaved ranges waiting to be merged,
+        // go ahead and do it
+        if (!intlv_ranges.empty()) {
+            DPRINTF(AddrRanges, "-- Merging range from %d ranges\n",
+                    intlv_ranges.size());
+            AddrRange merged_range(intlv_ranges);
+            if (!(useDefaultRange && merged_range.isSubset(defaultRange))) {
+                xbarRanges.push_back(merged_range);
+                DPRINTF(AddrRanges, "-- Adding merged range %s\n",
+                        merged_range.to_string());
+            }
+        }
+
+        // also check that no range partially overlaps with the
+        // default range, this has to be done after all ranges are set
+        // as there are no guarantees for when the default range is
+        // update with respect to the other ones
+        if (useDefaultRange) {
+            for (const auto& r: xbarRanges) {
+                // see if the new range is partially
+                // overlapping the default range
+                if (r.intersects(defaultRange) &&
+                    !r.isSubset(defaultRange))
+                    fatal("Range %s intersects the "                    \
+                          "default range of %s but is not a "           \
+                          "subset\n", r.to_string(), name());
+            }
+        }
+
+        // tell all our neighbouring master ports that our address
+        // ranges have changed
+        for (const auto& s: slavePorts)
+            s->sendRangeChange();
+    }
+
+    clearPortCache();
+}
+
+AddrRangeList
+BaseXBar::getAddrRanges() const
+{
+    // we should never be asked without first having sent a range
+    // change, and the latter is only done once we have all the ranges
+    // of the connected devices
+    assert(gotAllAddrRanges);
+
+    // at the moment, this never happens, as there are no cycles in
+    // the range queries and no devices on the master side of a crossbar
+    // (CPU, cache, bridge etc) actually care about the ranges of the
+    // ports they are connected to
+
+    DPRINTF(AddrRanges, "Received address range request\n");
+
+    return xbarRanges;
+}
+
+void
+BaseXBar::regStats()
+{
+    using namespace Stats;
+
+    transDist
+        .init(MemCmd::NUM_MEM_CMDS)
+        .name(name() + ".trans_dist")
+        .desc("Transaction distribution")
+        .flags(nozero);
+
+    // get the string representation of the commands
+    for (int i = 0; i < MemCmd::NUM_MEM_CMDS; i++) {
+        MemCmd cmd(i);
+        const std::string &cstr = cmd.toString();
+        transDist.subname(i, cstr);
+    }
+
+    pktCount
+        .init(slavePorts.size(), masterPorts.size())
+        .name(name() + ".pkt_count")
+        .desc("Packet count per connected master and slave (bytes)")
+        .flags(total | nozero | nonan);
+
+    pktSize
+        .init(slavePorts.size(), masterPorts.size())
+        .name(name() + ".pkt_size")
+        .desc("Cumulative packet size per connected master and slave (bytes)")
+        .flags(total | nozero | nonan);
+
+    // both the packet count and total size are two-dimensional
+    // vectors, indexed by slave port id and master port id, thus the
+    // neighbouring master and slave, they do not differentiate what
+    // came from the master and was forwarded to the slave (requests
+    // and snoop responses) and what came from the slave and was
+    // forwarded to the master (responses and snoop requests)
+    for (int i = 0; i < slavePorts.size(); i++) {
+        pktCount.subname(i, slavePorts[i]->getMasterPort().name());
+        pktSize.subname(i, slavePorts[i]->getMasterPort().name());
+        for (int j = 0; j < masterPorts.size(); j++) {
+            pktCount.ysubname(j, masterPorts[j]->getSlavePort().name());
+            pktSize.ysubname(j, masterPorts[j]->getSlavePort().name());
+        }
+    }
+}
+
+template <typename SrcType, typename DstType>
+unsigned int
+BaseXBar::Layer<SrcType,DstType>::drain(DrainManager *dm)
+{
+    //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 (state != IDLE) {
+        DPRINTF(Drain, "Crossbar not drained\n");
+        drainManager = dm;
+        return 1;
+    }
+    return 0;
+}
+
+template <typename SrcType, typename DstType>
+void
+BaseXBar::Layer<SrcType,DstType>::regStats()
+{
+    using namespace Stats;
+
+    occupancy
+        .name(name() + ".occupancy")
+        .desc("Layer occupancy (ticks)")
+        .flags(nozero);
+
+    utilization
+        .name(name() + ".utilization")
+        .desc("Layer utilization (%)")
+        .precision(1)
+        .flags(nozero);
+
+    utilization = 100 * occupancy / simTicks;
+}
+
+/**
+ * Crossbar layer template instantiations. Could be removed with _impl.hh
+ * file, but since there are only two given options (MasterPort and
+ * SlavePort) it seems a bit excessive at this point.
+ */
+template class BaseXBar::Layer<SlavePort,MasterPort>;
+template class BaseXBar::Layer<MasterPort,SlavePort>;