XBar.py (10719:b4fc9ad648aa) XBar.py (10720:67b3e74de9ae)
1# Copyright (c) 2012, 2015 ARM Limited
2# All rights reserved.
3#
4# The license below extends only to copyright in the software and shall
5# not be construed as granting a license to any other intellectual
6# property including but not limited to intellectual property relating
7# to a hardware implementation of the functionality of the software
8# licensed hereunder. You may use the software subject to the license

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61 #
62 # A request incurs the frontend latency, possibly snoop filter
63 # lookup latency, and forward latency. A response incurs the
64 # response latency. Frontend latency encompasses arbitration and
65 # deciding what to do when a request arrives. the forward latency
66 # is the latency involved once a decision is made to forward the
67 # request. The response latency, is similar to the forward
68 # latency, but for responses rather than requests.
1# Copyright (c) 2012, 2015 ARM Limited
2# All rights reserved.
3#
4# The license below extends only to copyright in the software and shall
5# not be construed as granting a license to any other intellectual
6# property including but not limited to intellectual property relating
7# to a hardware implementation of the functionality of the software
8# licensed hereunder. You may use the software subject to the license

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61 #
62 # A request incurs the frontend latency, possibly snoop filter
63 # lookup latency, and forward latency. A response incurs the
64 # response latency. Frontend latency encompasses arbitration and
65 # deciding what to do when a request arrives. the forward latency
66 # is the latency involved once a decision is made to forward the
67 # request. The response latency, is similar to the forward
68 # latency, but for responses rather than requests.
69 frontend_latency = Param.Cycles(3, "Frontend latency")
70 forward_latency = Param.Cycles(4, "Forward latency")
71 response_latency = Param.Cycles(2, "Response latency")
69 frontend_latency = Param.Cycles("Frontend latency")
70 forward_latency = Param.Cycles("Forward latency")
71 response_latency = Param.Cycles("Response latency")
72
73 # Width governing the throughput of the crossbar
72
73 # Width governing the throughput of the crossbar
74 width = Param.Unsigned(8, "Datapath width per port (bytes)")
74 width = Param.Unsigned("Datapath width per port (bytes)")
75
76 # The default port can be left unconnected, or be used to connect
77 # a default slave port
78 default = MasterPort("Port for connecting an optional default slave")
79
80 # The default port can be used unconditionally, or based on
81 # address range, in which case it may overlap with other
82 # ports. The default range is always checked first, thus creating

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90 cxx_header = "mem/noncoherent_xbar.hh"
91
92class CoherentXBar(BaseXBar):
93 type = 'CoherentXBar'
94 cxx_header = "mem/coherent_xbar.hh"
95
96 # The coherent crossbar additionally has snoop responses that are
97 # forwarded after a specific latency.
75
76 # The default port can be left unconnected, or be used to connect
77 # a default slave port
78 default = MasterPort("Port for connecting an optional default slave")
79
80 # The default port can be used unconditionally, or based on
81 # address range, in which case it may overlap with other
82 # ports. The default range is always checked first, thus creating

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90 cxx_header = "mem/noncoherent_xbar.hh"
91
92class CoherentXBar(BaseXBar):
93 type = 'CoherentXBar'
94 cxx_header = "mem/coherent_xbar.hh"
95
96 # The coherent crossbar additionally has snoop responses that are
97 # forwarded after a specific latency.
98 snoop_response_latency = Param.Cycles(4, "Snoop response latency")
98 snoop_response_latency = Param.Cycles("Snoop response latency")
99
100 # An optional snoop filter
101 snoop_filter = Param.SnoopFilter(NULL, "Selected snoop filter")
102
103 system = Param.System(Parent.any, "System that the crossbar belongs to.")
104
105class SnoopFilter(SimObject):
106 type = 'SnoopFilter'
107 cxx_header = "mem/snoop_filter.hh"
108
109 # Lookup latency of the snoop filter, added to requests that pass
110 # through a coherent crossbar.
111 lookup_latency = Param.Cycles(1, "Lookup latency")
112
113 system = Param.System(Parent.any, "System that the crossbar belongs to.")
99
100 # An optional snoop filter
101 snoop_filter = Param.SnoopFilter(NULL, "Selected snoop filter")
102
103 system = Param.System(Parent.any, "System that the crossbar belongs to.")
104
105class SnoopFilter(SimObject):
106 type = 'SnoopFilter'
107 cxx_header = "mem/snoop_filter.hh"
108
109 # Lookup latency of the snoop filter, added to requests that pass
110 # through a coherent crossbar.
111 lookup_latency = Param.Cycles(1, "Lookup latency")
112
113 system = Param.System(Parent.any, "System that the crossbar belongs to.")
114
115# We use a coherent crossbar to connect multiple masters to the L2
116# caches. Normally this crossbar would be part of the cache itself.
117class L2XBar(CoherentXBar):
118 # 256-bit crossbar by default
119 width = 32
120
121 # Assume that most of this is covered by the cache latencies, with
122 # no more than a single pipeline stage for any packet.
123 frontend_latency = 1
124 forward_latency = 0
125 response_latency = 1
126 snoop_response_latency = 1
127
128# One of the key coherent crossbar instances is the system
129# interconnect, tying together the CPU clusters, GPUs, and any I/O
130# coherent masters, and DRAM controllers.
131class SystemXBar(CoherentXBar):
132 # 128-bit crossbar by default
133 width = 16
134
135 # A handful pipeline stages for each portion of the latency
136 # contributions.
137 frontend_latency = 3
138 forward_latency = 4
139 response_latency = 2
140 snoop_response_latency = 4
141
142# In addition to the system interconnect, we typically also have one
143# or more on-chip I/O crossbars. Note that at some point we might want
144# to also define an off-chip I/O crossbar such as PCIe.
145class IOXBar(NoncoherentXBar):
146 # 128-bit crossbar by default
147 width = 16
148
149 # Assume a simpler datapath than a coherent crossbar, incuring
150 # less pipeline stages for decision making and forwarding of
151 # requests.
152 frontend_latency = 2
153 forward_latency = 1
154 response_latency = 2