arm: Share a port for the two table walker objects

This patch changes how the MMU and table walkers are created such that
a single port is used to connect the MMU and the TLBs to the memory
system. Previously two ports were needed as there are two table walker
objects (stage one and stage two), and they both had a port. Now the
port itself is moved to the Stage2MMU, and each TableWalker is simply
using the port from the parent.

By using the same port we also remove the need for having an
additional crossbar joining the two ports before the walker cache or
the L2. This simplifies the creation of the CPU cache topology in
BaseCPU.py considerably. Moreover, for naming and symmetry reasons,
the TLB walker port is connected through the stage-one table walker
thus making the naming identical to x86. Along the same line, we use
the stage-one table walker to generate the master id that is used by
all TLB-related requests.

1 files changed, 3 insertions, 23 deletions

diff --git a/src/cpu/BaseCPU.py b/src/cpu/BaseCPU.py
index 052df5702..ee6c05f46 100644
--- a/src/cpu/BaseCPU.py
+++ b/src/cpu/BaseCPU.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2012-2013 ARM Limited
+# Copyright (c) 2012-2013, 2015 ARM Limited
 # All rights reserved.
 #
 # The license below extends only to copyright in the software and shall
@@ -214,9 +214,6 @@ class BaseCPU(MemObject):
 
     if buildEnv['TARGET_ISA'] in ['x86', 'arm']:
         _cached_ports += ["itb.walker.port", "dtb.walker.port"]
-        if buildEnv['TARGET_ISA'] in ['arm']:
-            _cached_ports += ["istage2_mmu.stage2_tlb.walker.port",
-                              "dstage2_mmu.stage2_tlb.walker.port"]
 
     _uncached_slave_ports = []
     _uncached_master_ports = []
@@ -273,35 +270,18 @@ class BaseCPU(MemObject):
             if iwc and dwc:
                 self.itb_walker_cache = iwc
                 self.dtb_walker_cache = dwc
-                if buildEnv['TARGET_ISA'] in ['arm']:
-                    self.itb_walker_cache_bus = CoherentXBar()
-                    self.dtb_walker_cache_bus = CoherentXBar()
-                    self.itb_walker_cache_bus.master = iwc.cpu_side
-                    self.dtb_walker_cache_bus.master = dwc.cpu_side
-                    self.itb.walker.port = self.itb_walker_cache_bus.slave
-                    self.dtb.walker.port = self.dtb_walker_cache_bus.slave
-                    self.istage2_mmu.stage2_tlb.walker.port = self.itb_walker_cache_bus.slave
-                    self.dstage2_mmu.stage2_tlb.walker.port = self.dtb_walker_cache_bus.slave
-                else:
-                    self.itb.walker.port = iwc.cpu_side
-                    self.dtb.walker.port = dwc.cpu_side
+                self.itb.walker.port = iwc.cpu_side
+                self.dtb.walker.port = dwc.cpu_side
                 self._cached_ports += ["itb_walker_cache.mem_side", \
                                        "dtb_walker_cache.mem_side"]
             else:
                 self._cached_ports += ["itb.walker.port", "dtb.walker.port"]
 
-                if buildEnv['TARGET_ISA'] in ['arm']:
-                    self._cached_ports += ["istage2_mmu.stage2_tlb.walker.port", \
-                                           "dstage2_mmu.stage2_tlb.walker.port"]
-
             # Checker doesn't need its own tlb caches because it does
             # functional accesses only
             if self.checker != NULL:
                 self._cached_ports += ["checker.itb.walker.port", \
                                        "checker.dtb.walker.port"]
-                if buildEnv['TARGET_ISA'] in ['arm']:
-                    self._cached_ports += ["checker.istage2_mmu.stage2_tlb.walker.port", \
-                                           "checker.dstage2_mmu.stage2_tlb.walker.port"]
 
     def addTwoLevelCacheHierarchy(self, ic, dc, l2c, iwc = None, dwc = None):
         self.addPrivateSplitL1Caches(ic, dc, iwc, dwc)