MEM: Make the bus bridge unidirectional and fixed address range

This patch makes the bus bridge uni-directional and specialises the
bus ports to be a master port and a slave port. This greatly
simplifies the assumptions on both sides as either port only has to
deal with requests or responses. The following patches introduce the
notion of master and slave ports, and would not be possible without
this split of responsibilities.

In making the bridge unidirectional, the address range mechanism of
the bridge is also changed. For the cases where communication is
taking place both ways, an additional bridge is needed. This causes
issues with the existing mechanism, as the busses cannot determine
when to stop iterating the address updates from the two bridges. To
avoid this issue, and also greatly simplify the specification, the
bridge now has a fixed set of address ranges, specified at creation
time.

src/dev/arm/RealView.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2009 ARM Limited
+# Copyright (c) 2009-2011 ARM Limited
 # All rights reserved.
 #
 # The license below extends only to copyright in the software and shall
@@ -177,12 +177,18 @@ class RealViewPBX(RealView):
     rtc_fake      = AmbaFake(pio_addr=0x10017000, amba_id=0x41031)
 
 
-    # Attach I/O devices that are on chip
-    def attachOnChipIO(self, bus):
+    # Attach I/O devices that are on chip and also set the appropriate
+    # ranges for the bridge
+    def attachOnChipIO(self, bus, bridge):
        self.gic.pio = bus.port
        self.l2x0_fake.pio = bus.port
        self.a9scu.pio = bus.port
        self.local_cpu_timer.pio = bus.port
+       # Bridge ranges based on excluding what is part of on-chip I/O
+       # (gic, l2x0, a9scu, local_cpu_timer)
+       bridge.ranges = [AddrRange(self.realview_io.pio_addr,
+                                  self.a9scu.pio_addr - 1),
+                        AddrRange(self.flash_fake.pio_addr, Addr.max)]
 
     # Attach I/O devices to specified bus object.  Can't do this
     # earlier, since the bus object itself is typically defined at the
@@ -248,10 +254,16 @@ class RealViewEB(RealView):
 
 
 
-    # Attach I/O devices that are on chip
-    def attachOnChipIO(self, bus):
+    # Attach I/O devices that are on chip and also set the appropriate
+    # ranges for the bridge
+    def attachOnChipIO(self, bus, bridge):
        self.gic.pio = bus.port
        self.l2x0_fake.pio = bus.port
+       # Bridge ranges based on excluding what is part of on-chip I/O
+       # (gic, l2x0)
+       bridge.ranges = [AddrRange(self.realview_io.pio_addr,
+                                  self.gic.cpu_addr - 1),
+                        AddrRange(self.flash_fake.pio_addr, Addr.max)]
 
     # Attach I/O devices to specified bus object.  Can't do this
     # earlier, since the bus object itself is typically defined at the
@@ -329,10 +341,15 @@ class VExpress_ELT(RealView):
     usb_fake       = IsaFake(pio_addr=0xFB000000, pio_size=0x1ffff)
 
 
-    # Attach I/O devices that are on chip
-    def attachOnChipIO(self, bus):
+    # Attach I/O devices that are on chip and also set the appropriate
+    # ranges for the bridge
+    def attachOnChipIO(self, bus, bridge):
        self.gic.pio = bus.port
        self.a9scu.pio = bus.port
+       # Bridge ranges based on excluding what is part of on-chip I/O
+       # (gic, a9scu)
+       bridge.ranges = [AddrRange(self.pci_cfg_base, self.a9scu.pio_addr - 1),
+                        AddrRange(self.local_cpu_timer.pio_addr, Addr.max)]
 
     # Attach I/O devices to specified bus object.  Can't do this
     # earlier, since the bus object itself is typically defined at the