MEM: Introduce the master/slave port roles in the Python classes

This patch classifies all ports in Python as either Master or Slave
and enforces a binding of master to slave. Conceptually, a master (such
as a CPU or DMA port) issues requests, and receives responses, and
conversely, a slave (such as a memory or a PIO device) receives
requests and sends back responses. Currently there is no
differentiation between coherent and non-coherent masters and slaves.

The classification as master/slave also involves splitting the dual
role port of the bus into a master and slave port and updating all the
system assembly scripts to use the appropriate port. Similarly, the
interrupt devices have to have their int_port split into a master and
slave port. The intdev and its children have minimal changes to
facilitate the extra port.

Note that this patch does not enforce any port typing in the C++
world, it merely ensures that the Python objects have a notion of the
port roles and are connected in an appropriate manner. This check is
carried when two ports are connected, e.g. bus.master =
memory.port. The following patches will make use of the
classifications and specialise the C++ ports into masters and slaves.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/dev/Device.py b/src/dev/Device.py
index c32946277..96c95ebc9 100644
--- a/src/dev/Device.py
+++ b/src/dev/Device.py
@@ -33,7 +33,7 @@ from MemObject import MemObject
 class PioDevice(MemObject):
     type = 'PioDevice'
     abstract = True
-    pio = Port("Programmed I/O port")
+    pio = SlavePort("Programmed I/O port")
     system = Param.System(Parent.any, "System this device is part of")
 
 class BasicPioDevice(PioDevice):
@@ -45,7 +45,7 @@ class BasicPioDevice(PioDevice):
 class DmaDevice(PioDevice):
     type = 'DmaDevice'
     abstract = True
-    dma = Port("DMA port")
+    dma = MasterPort("DMA port")
     min_backoff_delay = Param.Latency('4ns',
       "min time between a nack packet being received and the next request made by the device")
     max_backoff_delay = Param.Latency('10us',