configs: Use absolute import paths

Use absoluate import paths to be Python 3 compatible. This also
imports absolute_import from __future__ to ensure that Python 2.7
behaves the same way as Python 3.

Change-Id: Ica06ed95814e9cd3e768b3e1785075e36f6e56d0
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16708
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

configs: Fix Python 3 iterator and exec compatibility issues

Python 2.7 used to return lists for operations such as map and range,
this has changed in Python 3. To make the configs Python 3 compliant,
add explicit conversions from iterators to lists where needed, replace
xrange with range, and fix changes to exec syntax.

This change doesn't fix import paths since that might require us to
restructure the configs slightly.

Change-Id: Idcea8482b286779fc98b4e144ca8f54069c08024
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/16002
Reviewed-by: Gabe Black <gabeblack@google.com>

config, mem, hmc: fix HMC test script

This patch keeps the logic behind the HMC model implementation untouched.

Additional changes:
- simple hello world script using HMC (SE simulation)

Usage examples:

./build/ARM/gem5.opt configs/example/hmctest.py
./build/ARM/gem5.opt configs/example/hmctest.py --enable-global-monitor --enable-link-monitor --arch=same
./build/ARM/gem5.opt configs/example/hmctest.py --enable-global-monitor --enable-link-monitor --arch=mixed
./build/ARM/gem5.opt configs/example/hmc_hello.py
./build/ARM/gem5.opt configs/example/hmc_hello.py --enable-global-monitor --enable-link-monitor

Change-Id: I64eb6c9abb45376b6ed72722926acddd50765394
Reviewed-on: https://gem5-review.googlesource.com/6061
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

mem: Update DRAM configuration names

Names of DRAM configurations were updated to reflect both
the channel and device data width.

Previous naming format was:
<DEVICE_TYPE>_<DATA_RATE>_<CHANNEL_WIDTH>

The following nomenclature is now used:
<DEVICE_TYPE>_<DATA_RATE>_<n>x<w>
where n = The number of devices per rank on the channel
x = Device width

Total channel width can be calculated by n*w

Example:
A 64-bit DDR4, 2400 channel consisting of 4-bit devices:
n = 16
w = 4
The resulting configuration name is:
DDR4_2400_16x4

Updated scripts to match new naming convention.

Added unique configurations for DDR4 for:
1) 16x4
2) 8x8
3) 4x16

Change-Id: Ibd7f763b7248835c624309143cb9fc29d56a69d1
Reviewed-by: Radhika Jagtap <radhika.jagtap@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>

mem: different HMC configuration

In this new hmc configuration we have used the existing components in gem5
mainly [SerialLink] [NoncoherentXbar]& [DRAMCtrl] to define 3 different
architecture for HMC.

Highlights

1- It explores 3 different HMC architectures

2- It creates 4-HMC crossbars and attaches 16 vault controllers with it.
This will connect vaults to serial links

3- From the previous version, HMCController with round robin funtionality
is being removed and all the serial links are being accessible directly
from user ports

4- Latency incorporated by HMCController (in previous version) is being
added to SerialLink

Committed by Jason Lowe-Power <jason@lowepower.com>

configs: Fix inheritance of HMCSystem and cleanup spacing

Minor fix to ensure the HMCSystem can actually be instantiated
(SimObject cannot be created). Also address some spacing issues.

configs: fix bug introduced due to 276ad9121192

I had made a typo in changeset 276ad9121192. This changeset fixes it

mem: hmc: top level design

This patch enables modeling a complete Hybrid Memory Cube (HMC) device. It
highly reuses the existing components in gem5's general memory system with some
small modifications. This changeset requires additional patches to model a
complete HMC device.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>