Bus: Split the bus into a non-coherent and coherent bus

This patch introduces a class hierarchy of buses, a non-coherent one,
and a coherent one, splitting the existing bus functionality. By doing
so it also enables further specialisation of the two types of buses.

A non-coherent bus connects a number of non-snooping masters and
slaves, and routes the request and response packets based on the
address. The request packets issued by the master connected to a
non-coherent bus could still snoop in caches attached to a coherent
bus, as is the case with the I/O bus and memory bus in most system
configurations. No snoops will, however, reach any master on the
non-coherent bus itself. The non-coherent bus can be used as a
template for modelling PCI, PCIe, and non-coherent AMBA and OCP buses,
and is typically used for the I/O buses.

A coherent bus connects a number of (potentially) snooping masters and
slaves, and routes the request and response packets based on the
address, and also forwards all requests to the snoopers and deals with
the snoop responses. The coherent bus can be used as a template for
modelling QPI, HyperTransport, ACE and coherent OCP buses, and is
typically used for the L1-to-L2 buses and as the main system
interconnect.

The configuration scripts are updated to use a NoncoherentBus for all
peripheral and I/O buses.

A bit of minor tidying up has also been done.

--HG--
rename : src/mem/bus.cc => src/mem/coherent_bus.cc
rename : src/mem/bus.hh => src/mem/coherent_bus.hh
rename : src/mem/bus.cc => src/mem/noncoherent_bus.cc
rename : src/mem/bus.hh => src/mem/noncoherent_bus.hh

1 files changed, 493 insertions, 0 deletions

diff --git a/src/mem/coherent_bus.cc b/src/mem/coherent_bus.cc
new file mode 100644
index 000000000..b40e84762
--- /dev/null
+++ b/src/mem/coherent_bus.cc
@@ -0,0 +1,493 @@
+/*
+ * Copyright (c) 2011-2012 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 bus object.
+ */
+
+#include "base/misc.hh"
+#include "base/trace.hh"
+#include "debug/BusAddrRanges.hh"
+#include "debug/CoherentBus.hh"
+#include "mem/coherent_bus.hh"
+
+CoherentBus::CoherentBus(const CoherentBusParams *p)
+    : BaseBus(p)
+{
+    // create the ports based on the size of the master and slave
+    // vector ports, and the presence of the default port, the ports
+    // are enumerated starting from zero
+    for (int i = 0; i < p->port_master_connection_count; ++i) {
+        std::string portName = csprintf("%s-p%d", name(), i);
+        MasterPort* bp = new CoherentBusMasterPort(portName, *this, i);
+        masterPorts.push_back(bp);
+    }
+
+    // see if we have a default slave device connected and if so add
+    // our corresponding master port
+    if (p->port_default_connection_count) {
+        defaultPortID = masterPorts.size();
+        std::string portName = csprintf("%s-default", name());
+        MasterPort* bp = new CoherentBusMasterPort(portName, *this,
+                                                   defaultPortID);
+        masterPorts.push_back(bp);
+    }
+
+    // create the slave ports, once again starting at zero
+    for (int i = 0; i < p->port_slave_connection_count; ++i) {
+        std::string portName = csprintf("%s-p%d", name(), i);
+        SlavePort* bp = new CoherentBusSlavePort(portName, *this, i);
+        slavePorts.push_back(bp);
+    }
+
+    clearPortCache();
+}
+
+void
+CoherentBus::init()
+{
+    // iterate over our slave ports and determine which of our
+    // neighbouring master ports are snooping and add them as snoopers
+    for (SlavePortConstIter p = slavePorts.begin(); p != slavePorts.end();
+         ++p) {
+        if ((*p)->getMasterPort().isSnooping()) {
+            DPRINTF(BusAddrRanges, "Adding snooping master %s\n",
+                    (*p)->getMasterPort().name());
+            snoopPorts.push_back(*p);
+        }
+    }
+
+    if (snoopPorts.empty())
+        warn("CoherentBus %s has no snooping ports attached!\n", name());
+}
+
+bool
+CoherentBus::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
+{
+    // determine the source port based on the id
+    SlavePort *src_port = slavePorts[slave_port_id];
+
+    // test if the bus should be considered occupied for the current
+    // port, and exclude express snoops from the check
+    if (!pkt->isExpressSnoop() && isOccupied(src_port)) {
+        DPRINTF(CoherentBus, "recvTimingReq: src %s %s 0x%x BUSY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
+        return false;
+    }
+
+    DPRINTF(CoherentBus, "recvTimingReq: src %s %s 0x%x\n",
+            src_port->name(), pkt->cmdString(), pkt->getAddr());
+
+    // set the source port for routing of the response
+    pkt->setSrc(slave_port_id);
+
+    Tick headerFinishTime = pkt->isExpressSnoop() ? 0 : calcPacketTiming(pkt);
+    Tick packetFinishTime = pkt->isExpressSnoop() ? 0 : pkt->finishTime;
+
+    // uncacheable requests need never be snooped
+    if (!pkt->req->isUncacheable()) {
+        // the packet is a memory-mapped request and should be
+        // broadcasted to our snoopers but the source
+        forwardTiming(pkt, slave_port_id);
+    }
+
+    // remember if we add an outstanding req so we can undo it if
+    // necessary, if the packet needs a response, we should add it
+    // as outstanding and express snoops never fail so there is
+    // not need to worry about them
+    bool add_outstanding = !pkt->isExpressSnoop() && pkt->needsResponse();
+
+    // keep track that we have an outstanding request packet
+    // matching this request, this is used by the coherency
+    // mechanism in determining what to do with snoop responses
+    // (in recvTimingSnoop)
+    if (add_outstanding) {
+        // we should never have an exsiting request outstanding
+        assert(outstandingReq.find(pkt->req) == outstandingReq.end());
+        outstandingReq.insert(pkt->req);
+    }
+
+    // since it is a normal request, determine the destination
+    // based on the address and attempt to send the packet
+    bool success = masterPorts[findPort(pkt->getAddr())]->sendTimingReq(pkt);
+
+    if (!success)  {
+        // inhibited packets should never be forced to retry
+        assert(!pkt->memInhibitAsserted());
+
+        // if it was added as outstanding and the send failed, then
+        // erase it again
+        if (add_outstanding)
+            outstandingReq.erase(pkt->req);
+
+        DPRINTF(CoherentBus, "recvTimingReq: src %s %s 0x%x RETRY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
+
+        addToRetryList(src_port);
+        occupyBus(headerFinishTime);
+
+        return false;
+    }
+
+    succeededTiming(packetFinishTime);
+
+    return true;
+}
+
+bool
+CoherentBus::recvTimingResp(PacketPtr pkt, PortID master_port_id)
+{
+    // determine the source port based on the id
+    MasterPort *src_port = masterPorts[master_port_id];
+
+    // test if the bus should be considered occupied for the current
+    // port
+    if (isOccupied(src_port)) {
+        DPRINTF(CoherentBus, "recvTimingResp: src %s %s 0x%x BUSY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
+        return false;
+    }
+
+    DPRINTF(CoherentBus, "recvTimingResp: src %s %s 0x%x\n",
+            src_port->name(), pkt->cmdString(), pkt->getAddr());
+
+    calcPacketTiming(pkt);
+    Tick packetFinishTime = pkt->finishTime;
+
+    // the packet is a normal response to a request that we should
+    // have seen passing through the bus
+    assert(outstandingReq.find(pkt->req) != outstandingReq.end());
+
+    // remove it as outstanding
+    outstandingReq.erase(pkt->req);
+
+    // send the packet to the destination through one of our slave
+    // ports, as determined by the destination field
+    bool success M5_VAR_USED = slavePorts[pkt->getDest()]->sendTimingResp(pkt);
+
+    // currently it is illegal to block responses... can lead to
+    // deadlock
+    assert(success);
+
+    succeededTiming(packetFinishTime);
+
+    return true;
+}
+
+void
+CoherentBus::recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id)
+{
+    DPRINTF(CoherentBus, "recvTimingSnoopReq: src %s %s 0x%x\n",
+            masterPorts[master_port_id]->name(), pkt->cmdString(),
+            pkt->getAddr());
+
+    // we should only see express snoops from caches
+    assert(pkt->isExpressSnoop());
+
+    // set the source port for routing of the response
+    pkt->setSrc(master_port_id);
+
+    // forward to all snoopers
+    forwardTiming(pkt, InvalidPortID);
+
+    // a snoop request came from a connected slave device (one of
+    // our master ports), and if it is not coming from the slave
+    // device responsible for the address range something is
+    // wrong, hence there is nothing further to do as the packet
+    // would be going back to where it came from
+    assert(master_port_id == findPort(pkt->getAddr()));
+
+    // this is an express snoop and is never forced to retry
+    assert(!inRetry);
+}
+
+bool
+CoherentBus::recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id)
+{
+    // determine the source port based on the id
+    SlavePort* src_port = slavePorts[slave_port_id];
+
+    // test if the bus should be considered occupied for the current
+    // port
+    if (isOccupied(src_port)) {
+        DPRINTF(CoherentBus, "recvTimingSnoopResp: src %s %s 0x%x BUSY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
+        return false;
+    }
+
+    DPRINTF(CoherentBus, "recvTimingSnoop: src %s %s 0x%x\n",
+            src_port->name(), pkt->cmdString(), pkt->getAddr());
+
+    // get the destination from the packet
+    PortID dest = pkt->getDest();
+
+    // responses are never express snoops
+    assert(!pkt->isExpressSnoop());
+
+    calcPacketTiming(pkt);
+    Tick packetFinishTime = pkt->finishTime;
+
+    // determine if the response is from a snoop request we
+    // created as the result of a normal request (in which case it
+    // should be in the outstandingReq), or if we merely forwarded
+    // someone else's snoop request
+    if (outstandingReq.find(pkt->req) == outstandingReq.end()) {
+        // this is a snoop response to a snoop request we
+        // forwarded, e.g. coming from the L1 and going to the L2
+        // this should be forwarded as a snoop response
+        bool success M5_VAR_USED = masterPorts[dest]->sendTimingSnoopResp(pkt);
+        assert(success);
+    } else {
+        // we got a snoop response on one of our slave ports,
+        // i.e. from a coherent master connected to the bus, and
+        // since we created the snoop request as part of
+        // recvTiming, this should now be a normal response again
+        outstandingReq.erase(pkt->req);
+
+        // this is a snoop response from a coherent master, with a
+        // destination field set on its way through the bus as
+        // request, hence it should never go back to where the
+        // snoop response came from, but instead to where the
+        // original request came from
+        assert(slave_port_id != dest);
+
+        // as a normal response, it should go back to a master
+        // through one of our slave ports
+        bool success M5_VAR_USED = slavePorts[dest]->sendTimingResp(pkt);
+
+        // currently it is illegal to block responses... can lead
+        // to deadlock
+        assert(success);
+    }
+
+    succeededTiming(packetFinishTime);
+
+    return true;
+}
+
+
+void
+CoherentBus::forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id)
+{
+    for (SlavePortIter s = snoopPorts.begin(); s != snoopPorts.end(); ++s) {
+        SlavePort *p = *s;
+        // 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 (exclude_slave_port_id == InvalidPortID ||
+            p->getId() != exclude_slave_port_id) {
+            // cache is not allowed to refuse snoop
+            p->sendTimingSnoopReq(pkt);
+        }
+    }
+}
+
+Tick
+CoherentBus::recvAtomic(PacketPtr pkt, PortID slave_port_id)
+{
+    DPRINTF(CoherentBus, "recvAtomic: packet src %s addr 0x%x cmd %s\n",
+            slavePorts[slave_port_id]->name(), pkt->getAddr(),
+            pkt->cmdString());
+
+    MemCmd snoop_response_cmd = MemCmd::InvalidCmd;
+    Tick snoop_response_latency = 0;
+
+    // uncacheable requests need never be snooped
+    if (!pkt->req->isUncacheable()) {
+        // forward to all snoopers but the source
+        std::pair<MemCmd, Tick> snoop_result =
+            forwardAtomic(pkt, slave_port_id);
+        snoop_response_cmd = snoop_result.first;
+        snoop_response_latency = snoop_result.second;
+    }
+
+    // even if we had a snoop response, we must continue and also
+    // perform the actual request at the destination
+    PortID dest_id = findPort(pkt->getAddr());
+
+    // forward the request to the appropriate destination
+    Tick response_latency = masterPorts[dest_id]->sendAtomic(pkt);
+
+    // if we got a response from a snooper, restore it here
+    if (snoop_response_cmd != MemCmd::InvalidCmd) {
+        // no one else should have responded
+        assert(!pkt->isResponse());
+        pkt->cmd = snoop_response_cmd;
+        response_latency = snoop_response_latency;
+    }
+
+    pkt->finishTime = curTick() + response_latency;
+    return response_latency;
+}
+
+Tick
+CoherentBus::recvAtomicSnoop(PacketPtr pkt, PortID master_port_id)
+{
+    DPRINTF(CoherentBus, "recvAtomicSnoop: packet src %s addr 0x%x cmd %s\n",
+            masterPorts[master_port_id]->name(), pkt->getAddr(),
+            pkt->cmdString());
+
+    // forward to all snoopers
+    std::pair<MemCmd, Tick> snoop_result =
+        forwardAtomic(pkt, InvalidPortID);
+    MemCmd snoop_response_cmd = snoop_result.first;
+    Tick snoop_response_latency = snoop_result.second;
+
+    if (snoop_response_cmd != MemCmd::InvalidCmd)
+        pkt->cmd = snoop_response_cmd;
+
+    pkt->finishTime = curTick() + snoop_response_latency;
+    return snoop_response_latency;
+}
+
+std::pair<MemCmd, Tick>
+CoherentBus::forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id)
+{
+    // the packet may be changed on snoops, 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;
+
+    for (SlavePortIter s = snoopPorts.begin(); s != snoopPorts.end(); ++s) {
+        SlavePort *p = *s;
+        // 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 (exclude_slave_port_id == InvalidPortID ||
+            p->getId() != exclude_slave_port_id) {
+            Tick latency = p->sendAtomicSnoop(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);
+                assert(pkt->memInhibitAsserted());
+                // should only happen once
+                assert(snoop_response_cmd == MemCmd::InvalidCmd);
+                // save response state
+                snoop_response_cmd = pkt->cmd;
+                snoop_response_latency = latency;
+                // restore original packet state for remaining snoopers
+                pkt->cmd = orig_cmd;
+            }
+        }
+    }
+
+    // the packet is restored as part of the loop and any potential
+    // snoop response is part of the returned pair
+    return std::make_pair(snoop_response_cmd, snoop_response_latency);
+}
+
+void
+CoherentBus::recvFunctional(PacketPtr pkt, PortID slave_port_id)
+{
+    if (!pkt->isPrint()) {
+        // don't do DPRINTFs on PrintReq as it clutters up the output
+        DPRINTF(CoherentBus,
+                "recvFunctional: packet src %s addr 0x%x cmd %s\n",
+                slavePorts[slave_port_id]->name(), pkt->getAddr(),
+                pkt->cmdString());
+    }
+
+    // uncacheable requests need never be snooped
+    if (!pkt->req->isUncacheable()) {
+        // forward to all snoopers but the source
+        forwardFunctional(pkt, slave_port_id);
+    }
+
+    // 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()) {
+        PortID dest_id = findPort(pkt->getAddr());
+
+        masterPorts[dest_id]->sendFunctional(pkt);
+    }
+}
+
+void
+CoherentBus::recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id)
+{
+    if (!pkt->isPrint()) {
+        // don't do DPRINTFs on PrintReq as it clutters up the output
+        DPRINTF(CoherentBus,
+                "recvFunctionalSnoop: packet src %s addr 0x%x cmd %s\n",
+                masterPorts[master_port_id]->name(), pkt->getAddr(),
+                pkt->cmdString());
+    }
+
+    // forward to all snoopers
+    forwardFunctional(pkt, InvalidPortID);
+}
+
+void
+CoherentBus::forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id)
+{
+    for (SlavePortIter s = snoopPorts.begin(); s != snoopPorts.end(); ++s) {
+        SlavePort *p = *s;
+        // 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 (exclude_slave_port_id == InvalidPortID ||
+            p->getId() != exclude_slave_port_id)
+            p->sendFunctionalSnoop(pkt);
+
+        // if we get a response we are done
+        if (pkt->isResponse()) {
+            break;
+        }
+    }
+}
+
+CoherentBus *
+CoherentBusParams::create()
+{
+    return new CoherentBus(this);
+}