mem: Add a WriteClean command to the packet class

A WriteClean packet allows a cache to write a block to a memory below
without evicting its copy. A typical usecase for a WriteClean packet
is a cache clean operation.

Change-Id: If356cb067da5ddf3210c135f41ef0891fb811568
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Anouk Van Laer <anouk.vanlaer@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5044
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

src/mem/packet.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011-2016 ARM Limited
+ * Copyright (c) 2011-2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -95,6 +95,9 @@ MemCmd::commandInfo[] =
      * dirty. */
     { SET5(IsWrite, IsRequest, IsEviction, HasData, FromCache),
             InvalidCmd, "WritebackClean" },
+    /* WriteClean - This allows a cache to write a dirty block to a memory
+       below without evicting its copy. */
+    { SET4(IsWrite, IsRequest, HasData, FromCache), InvalidCmd, "WriteClean" },
     /* CleanEvict */
     { SET3(IsRequest, IsEviction, FromCache), InvalidCmd, "CleanEvict" },
     /* SoftPFReq */

src/mem/packet.hh

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2016 ARM Limited
+ * Copyright (c) 2012-2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -88,6 +88,7 @@ class MemCmd
         WriteResp,
         WritebackDirty,
         WritebackClean,
+        WriteClean,            // writes dirty data below without evicting
         CleanEvict,
         SoftPFReq,
         HardPFReq,