# Copyright (c) 2021 The Regents of the University of California
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"""
This gem5 configuation script creates a simple board to run an ARM
"hello world" binary.

This is setup is the close to the simplest setup possible using the gem5
library. It does not contain any kind of caching, IO, or any non-essential
components.

Usage
-----

```
scons build/ARM/gem5.opt
./build/ARM/gem5.opt configs/example/gem5_library/arm-hello.py
```
"""

from gem5.isas import ISA
from gem5.utils.requires import requires
from gem5.resources.resource import Resource
from gem5.components.memory import SingleChannelDDR3_1600
from gem5.components.processors.cpu_types import CPUTypes
from gem5.components.boards.simple_board import SimpleBoard
from gem5.components.cachehierarchies.classic.no_cache import NoCache
from gem5.components.processors.simple_processor import SimpleProcessor
from gem5.simulate.simulator import Simulator

# This check ensures the gem5 binary is compiled to the ARM ISA target. If not,
# an exception will be thrown.
requires(isa_required=ISA.ARM)

# In this setup we don't have a cache. `NoCache` can be used for such setups.
cache_hierarchy = NoCache()

# We use a single channel DDR3_1600 memory system
memory = SingleChannelDDR3_1600(size="32MB")

# We use a simple Timing processor with one core.
processor = SimpleProcessor(cpu_type=CPUTypes.TIMING, isa=ISA.ARM, num_cores=1)

# The gem5 library simble board which can be used to run simple SE-mode
# simulations.
board = SimpleBoard(
    clk_freq="3GHz",
    processor=processor,
    memory=memory,
    cache_hierarchy=cache_hierarchy,
)

# Here we set the workload. In this case we want to run a simple "Hello World!"
# program compiled to the ARM ISA. The `Resource` class will automatically
# download the binary from the gem5 Resources cloud bucket if it's not already
# present.
board.set_se_binary_workload(
    # The `Resource` class reads the `resources.json` file from the gem5
    # resources repository:
    # https://gem5.googlesource.com/public/gem5-resource.
    # Any resource specified in this file will be automatically retrieved.
    # At the time of writing, this file is a WIP and does not contain all
    # resources. Jira ticket: https://gem5.atlassian.net/browse/GEM5-1096
    Resource("arm-hello64-static")
)

# Lastly we run the simulation.
simulator = Simulator(board=board)
simulator.run()

print(
    "Exiting @ tick {} because {}.".format(
        simulator.get_current_tick(),
        simulator.get_last_exit_event_cause(),
    )
)