From 860155a5fc48f983e9af40c19bf8db8250709c26 Mon Sep 17 00:00:00 2001
From: Andreas Hansson <andreas.hansson@arm.com>
Date: Tue, 19 Feb 2013 05:56:06 -0500
Subject: mem: Enforce strict use of busFirst- and busLastWordTime

This patch adds a check to ensure that the delay incurred by
the bus is not simply disregarded, but accounted for by someone. At
this point, all the modules do is to zero it out, and no additional
time is spent. This highlights where the bus timing is simply dropped
instead of being paid for.

As a follow up, the locations identified in this patch should add this
additional time to the packets in one way or another. For now it
simply acts as a sanity check and highlights where the delay is simply
ignored.

Since no time is added, all regressions remain the same.
---
 src/mem/cache/cache_impl.hh | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'src/mem/cache/cache_impl.hh')

diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh
index 8fd28728b..b30132748 100644
--- a/src/mem/cache/cache_impl.hh
+++ b/src/mem/cache/cache_impl.hh
@@ -381,6 +381,8 @@ Cache<TagStore>::recvTimingSnoopResp(PacketPtr pkt)
 
     pkt->setDest(rec->prevSrc);
     delete rec;
+    // @todo someone should pay for this
+    pkt->busFirstWordDelay = pkt->busLastWordDelay = 0;
     memSidePort->schedTimingSnoopResp(pkt, time);
 }
 
@@ -419,6 +421,9 @@ Cache<TagStore>::recvTimingReq(PacketPtr pkt)
         // supplier had exclusive copy to begin with.
         if (pkt->needsExclusive() && !pkt->isSupplyExclusive()) {
             Packet *snoopPkt = new Packet(pkt, true);  // clear flags
+            // also reset the bus time that the original packet has
+            // not yet paid for
+            snoopPkt->busFirstWordDelay = snoopPkt->busLastWordDelay = 0;
             snoopPkt->setExpressSnoop();
             snoopPkt->assertMemInhibit();
             memSidePort->sendTimingReq(snoopPkt);
@@ -437,6 +442,9 @@ Cache<TagStore>::recvTimingReq(PacketPtr pkt)
     if (pkt->req->isUncacheable()) {
         uncacheableFlush(pkt);
 
+        // @todo: someone should pay for this
+        pkt->busFirstWordDelay = pkt->busLastWordDelay = 0;
+
         // writes go in write buffer, reads use MSHR
         if (pkt->isWrite() && !pkt->isRead()) {
             allocateWriteBuffer(pkt, time, true);
@@ -489,6 +497,8 @@ Cache<TagStore>::recvTimingReq(PacketPtr pkt)
 
         if (needsResponse) {
             pkt->makeTimingResponse();
+            // @todo: Make someone pay for this
+            pkt->busFirstWordDelay = pkt->busLastWordDelay = 0;
             cpuSidePort->schedTimingResp(pkt, clockEdge(lat));
         } else {
             /// @todo nominally we should just delete the packet here,
@@ -499,6 +509,9 @@ Cache<TagStore>::recvTimingReq(PacketPtr pkt)
     } else {
         // miss
 
+        // @todo: Make someone pay for this
+        pkt->busFirstWordDelay = pkt->busLastWordDelay = 0;
+
         Addr blk_addr = blockAlign(pkt->getAddr());
         MSHR *mshr = mshrQueue.findMatch(blk_addr);
 
@@ -946,6 +959,8 @@ Cache<TagStore>::recvTimingResp(PacketPtr pkt)
                 // isInvalidate() set otherwise.
                 target->pkt->cmd = MemCmd::ReadRespWithInvalidate;
             }
+            // reset the bus additional time as it is now accounted for
+            target->pkt->busFirstWordDelay = target->pkt->busLastWordDelay = 0;
             cpuSidePort->schedTimingResp(target->pkt, completion_time);
             break;
 
@@ -1250,6 +1265,8 @@ doTimingSupplyResponse(PacketPtr req_pkt, uint8_t *blk_data,
     assert(req_pkt->isInvalidate() || pkt->sharedAsserted());
     pkt->allocate();
     pkt->makeTimingResponse();
+    // @todo Make someone pay for this
+    pkt->busFirstWordDelay = pkt->busLastWordDelay = 0;
     if (pkt->isRead()) {
         pkt->setDataFromBlock(blk_data, blkSize);
     }
@@ -1293,6 +1310,9 @@ Cache<TagStore>::handleSnoop(PacketPtr pkt, BlkType *blk,
             Packet snoopPkt(pkt, true);  // clear flags
             snoopPkt.setExpressSnoop();
             snoopPkt.pushSenderState(new ForwardResponseRecord(pkt->getSrc()));
+            // the snoop packet does not need to wait any additional
+            // time
+            snoopPkt.busFirstWordDelay = snoopPkt.busLastWordDelay = 0;
             cpuSidePort->sendTimingSnoopReq(&snoopPkt);
             if (snoopPkt.memInhibitAsserted()) {
                 // cache-to-cache response from some upper cache
-- 
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