mem: Support for specifying the destination of a WriteClean

Previously, WriteClean packets would always write to the first memory
below unless the memory was unable to allocate in which case it would
be forwarded further below.

This change adds support for specifying the destination of a
WriteClean packet. The cache annotates the request with the specified
destination and marks the packet as write-through upon its
creation. The coherent xbar checks packets for their destination and
resets the write-through flag when necessary e.g., the coherent xbar
that is set as the PoC will reset the write-through flag for packets
to the PoC.

Change-Id: I84b653f5cb6e46e97e09508649a3725d72d94606
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Anouk Van Laer <anouk.vanlaer@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5046
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

1 files changed, 22 insertions, 2 deletions

diff --git a/src/mem/request.hh b/src/mem/request.hh
index aff13075b..6fc98506c 100644
--- a/src/mem/request.hh
+++ b/src/mem/request.hh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2013 ARM Limited
+ * Copyright (c) 2012-2013,2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -87,7 +87,7 @@ typedef uint16_t MasterID;
 class Request
 {
   public:
-    typedef uint32_t FlagsType;
+    typedef uint64_t FlagsType;
     typedef uint8_t ArchFlagsType;
     typedef ::Flags<FlagsType> Flags;
 
@@ -182,6 +182,15 @@ class Request
         /** The request is a page table walk */
         PT_WALK                     = 0x20000000,
 
+        /** The request targets the point of unification */
+        DST_POU                     = 0x0000001000000000,
+
+        /** The request targets the point of coherence */
+        DST_POC                     = 0x0000002000000000,
+
+        /** Bits to define the destination of a request */
+        DST_BITS                    = 0x0000003000000000,
+
         /**
          * These flags are *not* cleared when a Request object is
          * reused (assigned a new address).
@@ -790,6 +799,17 @@ class Request
     }
 
     /**
+     * Accessor functions for the destination of a memory request. The
+     * destination flag can specify a point of reference for the
+     * operation (e.g. a cache block clean to the the point of
+     * unification). At the moment the destination is only used by the
+     * cache maintenance operations.
+     */
+    bool isToPOU() const { return _flags.isSet(DST_POU); }
+    bool isToPOC() const { return _flags.isSet(DST_POC); }
+    Flags getDest() const { return _flags & DST_BITS; }
+
+    /**
      * Accessor functions for the memory space configuration flags and used by
      * GPU ISAs such as the Heterogeneous System Architecture (HSA). Note that
      * these are for testing only; setting extraFlags should be done via