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, 28 insertions, 29 deletions

diff --git a/src/mem/packet.hh b/src/mem/packet.hh
index c070eaea7..4ed307f66 100644
--- a/src/mem/packet.hh
+++ b/src/mem/packet.hh
@@ -293,14 +293,14 @@ class Packet : public Printable
     /**
      * Source port identifier set on a request packet to enable
      * appropriate routing of the responses. The source port
-     * identifier is set by any multiplexing component, e.g. a bus, as
-     * the timing responses need this information to be routed back to
-     * the appropriate port at a later point in time. The field can be
-     * updated (over-written) as the request packet passes through
-     * additional multiplexing components, and it is their
-     * responsibility to remember the original source port identifier,
-     * for example by using an appropriate sender state. The latter is
-     * done in the cache and bridge.
+     * identifier is set by any multiplexing component, e.g. a
+     * crossbar, as the timing responses need this information to be
+     * routed back to the appropriate port at a later point in
+     * time. The field can be updated (over-written) as the request
+     * packet passes through additional multiplexing components, and
+     * it is their responsibility to remember the original source port
+     * identifier, for example by using an appropriate sender
+     * state. The latter is done in the cache and bridge.
      */
     PortID src;
 
@@ -309,7 +309,7 @@ class Packet : public Printable
      * packets that passed through a multiplexing component as a
      * request packet. The source port identifier is turned into a
      * destination port identifier when the packet is turned into a
-     * response, and the destination is used, e.g. by the bus, to
+     * response, and the destination is used, e.g. by the crossbar, to
      * select the appropriate path through the interconnect.
      */
     PortID dest;
@@ -333,21 +333,22 @@ class Packet : public Printable
 
     /**
      * The extra delay from seeing the packet until the first word is
-     * transmitted by the bus that provided it (if any). This delay is
-     * used to communicate the bus waiting time to the neighbouring
-     * object (e.g. a cache) that actually makes the packet wait. As
-     * the delay is relative, a 32-bit unsigned should be sufficient.
+     * transmitted. This delay is used to communicate the crossbar
+     * forwarding latency to the neighbouring object (e.g. a cache)
+     * that actually makes the packet wait. As the delay is relative,
+     * a 32-bit unsigned should be sufficient.
      */
-    uint32_t busFirstWordDelay;
+    uint32_t firstWordDelay;
 
     /**
-     * The extra delay from seeing the packet until the last word is
-     * transmitted by the bus that provided it (if any). Similar to
-     * the first word time, this is used to make up for the fact that
-     * the bus does not make the packet wait. As the delay is relative,
-     * a 32-bit unsigned should be sufficient.
+     * The extra pipelining delay from seeing the packet until the
+     * last word is transmitted by the component that provided it (if
+     * any). This includes the first word delay. Similar to the first
+     * word delay, this is used to make up for the fact that the
+     * crossbar does not make the packet wait. As the delay is
+     * relative, a 32-bit unsigned should be sufficient.
      */
-    uint32_t busLastWordDelay;
+    uint32_t lastWordDelay;
 
     /**
      * A virtual base opaque structure used to hold state associated
@@ -541,8 +542,6 @@ class Packet : public Printable
     PortID getSrc() const { assert(isSrcValid()); return src; }
     /// Accessor function to set the source index of the packet.
     void setSrc(PortID _src) { src = _src; }
-    /// Reset source field, e.g. to retransmit packet on different bus.
-    void clearSrc() { src = InvalidPortID; }
 
     bool isDestValid() const { return dest != InvalidPortID; }
     /// Accessor function for the destination index of the packet.
@@ -604,7 +603,7 @@ class Packet : public Printable
         :  cmd(_cmd), req(_req), data(nullptr), addr(0), _isSecure(false),
            src(InvalidPortID), dest(InvalidPortID),
            bytesValidStart(0), bytesValidEnd(0),
-           busFirstWordDelay(0), busLastWordDelay(0),
+           firstWordDelay(0), lastWordDelay(0),
            senderState(NULL)
     {
         if (req->hasPaddr()) {
@@ -627,7 +626,7 @@ class Packet : public Printable
         :  cmd(_cmd), req(_req), data(nullptr), addr(0), _isSecure(false),
            src(InvalidPortID), dest(InvalidPortID),
            bytesValidStart(0), bytesValidEnd(0),
-           busFirstWordDelay(0), busLastWordDelay(0),
+           firstWordDelay(0), lastWordDelay(0),
            senderState(NULL)
     {
         if (req->hasPaddr()) {
@@ -653,8 +652,8 @@ class Packet : public Printable
            src(pkt->src), dest(pkt->dest),
            bytesValidStart(pkt->bytesValidStart),
            bytesValidEnd(pkt->bytesValidEnd),
-           busFirstWordDelay(pkt->busFirstWordDelay),
-           busLastWordDelay(pkt->busLastWordDelay),
+           firstWordDelay(pkt->firstWordDelay),
+           lastWordDelay(pkt->lastWordDelay),
            senderState(pkt->senderState)
     {
         if (!clearFlags)
@@ -739,8 +738,8 @@ class Packet : public Printable
         dest = InvalidPortID;
         bytesValidStart = 0;
         bytesValidEnd = 0;
-        busFirstWordDelay = 0;
-        busLastWordDelay = 0;
+        firstWordDelay = 0;
+        lastWordDelay = 0;
 
         flags.set(VALID_ADDR|VALID_SIZE);
         deleteData();
@@ -766,7 +765,7 @@ class Packet : public Printable
         flags.clear(EXPRESS_SNOOP);
 
         dest = src;
-        clearSrc();
+        src = InvalidPortID;
     }
 
     void