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# Authors: Thomas Grass
#          Andreas Hansson
#          Sascha Bischoff

from m5.params import *
from m5.proxy import *
from MemObject import MemObject

# The traffic generator is a master module that generates stimuli for
# the memory system, based on a collection of simple behaviours that
# are either probabilistic or based on traces. It can be used stand
# alone for creating test cases for interconnect and memory
# controllers, or function as a black-box replacement for system
# components that are not yet modelled in detail, e.g. a video engine
# or baseband subsystem in an SoC.
#
# The traffic generator has a single master port that is used to send
# requests, independent of the specific behaviour. The behaviour of
# the traffic generator is specified in a configuration file, and this
# file describes a state transition graph where each state is a
# specific generator behaviour. Examples include idling, generating
# linear address sequences, random sequences and replay of captured
# traces. By describing these behaviours as states, it is straight
# forward to create very complex behaviours, simply by arranging them
# in graphs. The graph transitions can also be annotated with
# probabilities, effectively making it a Markov Chain.
class TrafficGen(MemObject):
    type = 'TrafficGen'
    cxx_header = "cpu/testers/traffic_gen/traffic_gen.hh"

    # Port used for sending requests and receiving responses
    port = MasterPort("Master port")

    # Config file to parse for the state descriptions
    config_file = Param.String("Configuration file describing the behaviour")

    # System used to determine the mode of the memory system
    system = Param.System(Parent.any, "System this generator is part of")

    # Should requests respond to back-pressure or not, if true, the
    # rate of the traffic generator will be slowed down if requests
    # are not immediately accepted
    elastic_req = Param.Bool(False,
                             "Slow down requests in case of backpressure")

    # Let the user know if we have waited for a retry and not made any
    # progress for a long period of time. The default value is
    # somewhat arbitrary and may well have to be tuned.
    progress_check = Param.Latency('1ms', "Time before exiting " \
                                   "due to lack of progress")