misc: Coupling gem5 with SystemC TLM2.0

Transaction Level Modeling (TLM2.0) is widely used in industry for creating
virtual platforms (IEEE 1666 SystemC). This patch contains a standard compliant
implementation of an external gem5 port, that enables the usage of gem5 as a
TLM initiator component in SystemC based virtual platforms. Both TLM coding
paradigms loosely timed (b_transport) and aproximately timed (nb_transport) are
supported.

Compared to the original patch a TLM memory manager was added. Furthermore, the
transaction object was removed and for each TLM payload a PacketPointer that
points to the original gem5 packet is added as an TLM extension.  For event
handling single events are now created.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>

configs/common/MemConfig.py

@@ -151,6 +151,15 @@ def config_mem(options, system):
     them.
     """
 
+    if options.tlm_memory:
+        system.external_memory = m5.objects.ExternalSlave(
+            port_type="tlm",
+            port_data=options.tlm_memory,
+            port=system.membus.master,
+            addr_ranges=system.mem_ranges)
+        system.kernel_addr_check = False
+        return
+
     if options.external_memory_system:
         system.external_memory = m5.objects.ExternalSlave(
             port_type=options.external_memory_system,