Recent breaking changes in the DRAMSys API require user code to be
updated. These updates have been applied to the gem5 integration.
Furthermore, as DRAMSys started to use CMake dependency management,
it is no longer sensible to maintain two separate build systems for
DRAMSys. The use of the DRAMSys integration in gem5 will therefore
from now on require that CMake is installed on the target machine.
Additionally, support for snapshots have been implemented into DRAMSys
and coupled with gem5's checkpointing API.
TracingExtension contains a stack recording the port names
passed through of the Packet. The target receiving the Packet
can dump out the whole path of this Packet for the debug purpose.
This mechanism can be enabled with the debug flag PortTrace.
Change-Id: Ic11e708b35fdddc4f4b786d91b35fd4def08948c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71538
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Yu-hsin Wang <yuhsingw@google.com>
The port_wrapper classes convert the Request/ResponsePort from
inherit-base to callback registrations. This help 'composition over
inheritance' that most design pattern follows, which help reducing
code length and increase reusability.
Change-Id: Ia13cc62507ac8425bd7cf143a2e080d041c173f9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67232
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
By default backdoor access fall back to atomic if not
implemented in the ResponsePort. Given this is a common
behavior for most of the IPs, having them print all the
warning creates large number of warning in a big system.
Ideally we want to make this a debug level log, but this
can only be done through the debug trace mechanism.
Change-Id: I8a4074fc58b13c1881ad62897a89774c66880ccb
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/60790
Reviewed-by: Yu-hsin Wang <yuhsingw@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
This change adds an hbm memory controller in gem5,
which is capable of controlling two hbm memory interfaces
(two pseudo channels). HBMCtrl inherits from MemCtrl
and tries to reuse most of the MemCtrl functions for two
different dram interfaces. Morever, a notion of pseudo
channel is added in the memory interface itself, to make
sure that the scheduling decisions in any interface are
based on the pkts for that pseudo channel only. Also, the
command bandwidth checks are divided into row and column
commands, which are shared by both pseudo channels.
Change-Id: Ie2ee8183d0f7f744aff2ed05cabc75fec3ea2171
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59732
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Wendy Elsasser <welsasser@rambus.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This change splits the default gem5 memory controller into two
memory controllers: MemCtrl (base memory controller which can be
used with only a single memory interface dram/nvm), and
HeteroMemCtrl (heterogeneous memory controller which inherits from
MemCtrl and requires a dram and an nvm memory interface).
New arguments are added to many of the base class (MemCtrl) functions
(for example memory inteface to use that function for) which helps
in easier use of these in the inherited class (HeteroMemCtrl).
Change-Id: Ifa4e9f9f1560c47063d1a8159a8c94add2e670bb
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59731
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
This change primarily splits the dram and nvm interfaces
into separate files. And also updates the interfaces so that
they can be handled in a more general way by the controller.
For example, both interfaces now override a virtual isBusy()
function defined in the mem_interface.
Change-Id: Id98bf0be3836a4b6245d5dea1b8fad0a60ce299a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59730
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
This makes what are configuration and what are internal SCons variables
explicit and separate, and makes it unnecessary to call out what
variables to export to C++.
These variables will also be plumbed into and out of kconfiglib in later
changes.
Change-Id: Iaf5e098d7404af06285c421dbdf8ef4171b3f001
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56892
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Add an utility class that provides a service for another process
query and get the fd of the corresponding region in gem5's physmem.
Basically, the service works in this way:
1. client connect to the unix socket created by a SharedMemoryServer
2. client send a request {start, end} to gem5
3. the server locates the corresponding shared memory
4. gem5 response {offset} and pass {fd} in ancillary data
mmap fd at offset will provide the client the view into the physical
memory of the request range.
Change-Id: I9d42fd8a41fc28dcfebb45dec10bc9ebb8e21d11
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/57729
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Boris Shingarov <shingarov@labware.com>
Tested-by: kokoro <noreply+kokoro@google.com>
It's possible to bridge together the memory interconnect of two
systems, either as parallel peers, or one nested inside the other. Each
System will have its own set of RequestorIDs, and using an ID from one
System inside the other can lead to a number of different problems.
This change adds a new SimObject called SysBridge which connects two
Systems interconnect together. The object allocates a requestor ID in
each system, and for all PacketPtrs passing through it, the requestor
ID from the target system is installed in the associated Request. On
the way back, either inline or in a split, delayed response, the
original RequestorID is restored by reinstalling the original Request
object.
Change-Id: I237c668962a04ef6dfc872df16762a884c05ede9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54743
Reviewed-by: Jesse Pai <jessepai@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This change adds the source code for the PortTerminator SimObject.
It could be used to connect request/response ports in the system
that can not be connected to any other ports. This will prevent
errors caused by orphan ports in the system. As an example if
you have set up a cache hierarchy and do not want to test its
performance in full system mode and want to use PyTrafficGen
instead, your system will end up with an icache or walker ports
that are not connected to anything. In this case, you can use a
PortTerminator to connect the orphan ports in your system.
Change-Id: I5e19cdd3ce064638ffabf29d29225eda77ffc146
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/51609
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
This class helps translate a region of memory one chunk at a time. The
generator returns an iterator through its begin and end methods which
can be used as part of a regular for loop, or as part of a range based
for loop. The iterator points to a Range object which holds the virtual
and physical address of the translation, the size of the region included
in the translation, and a Fault if the translation of that chunk
faulted.
When incrementing the iterator, if there was no fault it simply moves
ahead to the next region and attempts to translate it using a virtual
method implemented by subclasses. It's up to the subclass to determine
if there is now a fault, how many bytes have been translated if, for
instance, the page size is variable, and what the translated physical
address is.
If there was a fault, the iterator does not increment, it just clears
the fault and tries the previous translation again. This gives consumers
of the translation generator a chance to fix up faulting addresses
without having to abort the whole process and try again. This might be
useful if, for instance, you've reached the end of the stack and a new
page needs to be demand-paged in.
Change-Id: I8c4023845d989fe3781b1b73ab12f7c8855c9171
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/50758
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
CfiMemory: This is modelling a flash memory adhering to the
Common Flash Interface (CFI):
JEDEC JESD68.01
JEDEC JEP137B
Intel Application Note 646
This is as of now a pure functional model of a flash controller: no
timing/power information has been encoded in it and it is therefore not
representive of a real device. Some voltage/timing values have
nevertheless been encoded in the CFI table. This is just a requirement
from the CFI specification: guest software might query those entries,
but they are not reflected in gem5 statistics.
The model is meant to be used to allow execution of flash drivers (e.g.
UEFI firmware storing EFI variables in non volatile memory)
JIRA: https://gem5.atlassian.net/browse/GEM5-913
Change-Id: Id99e331ac8237f3ecb69d618da0d7ca7b038cd1f
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41495
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Make the actual controller more generic
- Rename DRAMCtrl to MemCtrl
- Rename DRAMacket to MemPacket
- Rename dram_ctrl.cc to mem_ctrl.cc
- Rename dram_ctrl.hh to mem_ctrl.hh
- Create MemCtrl debug flag
Move the memory interface classes/functions to separate files
- mem_interface.cc
- mem_interface.hh
Change-Id: I1acba44c855776343e205e7733a7d8bbba92a82c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/31654
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Add NVM interface to memory controller.
This can be used with or instead of the existing
DRAM interface. Therefore, a single controller can interface
to either DRAM or NVM, or both.
Specifically, a memory channel can be configured as:
- Memory controller interfacing to DRAM only
- Memory controller interfacing to NVM only
- Memory controller interfacing to both DRAM and NVM
How data is placed or migrated between media types is outside
of the scope of this change.
The NVM interface incorporates new static delay parameters
for read and write completion. The interface defines a 2
stage read to manage non-deterministic read delays while
enabling deterministic data transfer, similar to NVDIMM-P.
The NVM interface also includes parameters to define
read and write buffers on the media side (on-DIMM). These are
utilized to quickly offload commands and write data, mitigating
the effects of lower latency and bandwidth media characteristics.
Change-Id: I6b22ddb495877f88d161f0bd74ade32cc8fdcbcc
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29027
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Wendy Elsasser <wendy.elsasser@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Made DRAMCtrl a ClockedObject, with DRAMInterface
defined as an AbstractMemory. The address
ranges are now defined per interface. Currently
the model only includes a DRAMInterface but this
can be expanded for other media types.
The controller object includes a parameter to the
interface, which is setup when gem5 is configured.
Change-Id: I6a368b845d574a713c7196c5671188ca8c1dc5e8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28968
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Gem5 Hardware Transactional Memory (HTM)
Here we provide a brief note describing HTM support in Gem5 at
a high level.
HTM is an architectural feature that enables speculative concurrency in
a shared-memory system; groups of instructions known as transactions are
executed as an atomic unit. The system allows that transactions be
executed concurrently but intervenes if a transaction's
atomicity/isolation is jeapordised and takes corrective action. In this
implementation, corrective active explicitely means rolling back a
thread's architectural state and reverting any memory updates to a point
just before the transaction began.
This HTM implementation relies on--
(1) A checkpointing mechanism for architectural register state.
(2) Buffering speculative memory updates.
This patch is focusing on the definition of the HTM checkpoint (1)
The checkpointing mechanism is architecture dependent. Each ISA
leveraging HTM support can define a class HTMCheckpoint inhereting from
the generic one (GenericISA::HTMCheckpoint).
Those will need to save/restore the architectural state by overriding
the virtual HTMCheckpoint::save (when starting a transaction) and
HTMCheckpoint::restore (when aborting a transaction).
Instances of this class live in O3's ThreadState and Atomic's
SimpleThread. It is up to the ISA to populate this instance when
executing an instruction that begins a new transaction.
JIRA: https://gem5.atlassian.net/browse/GEM5-587
Change-Id: Icd8d1913d23652d78fe89e930ab1e302eb52363d
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30314
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Adds a TokenPort which uses tokens for flow control rather than the
standard retry mechanism in gem5. The port is intended to be used
for flow control where speculatively sending packets is not possible.
For example, GPU instructions require this to send memory requests
to the cache coalescer.
Change-Id: Id0d55ab65b7c773e97752b8514a780cdf7d88707
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27428
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This proxy was only used by the ARM semihosting interface which can now
use a tweaked regular TranslatingPortProxy or SETranslatingPortProxy
instead of this special purpose class.
This sort of class would still be necessary if you wanted to use
physical addresses and not virtual addresses, but presently there is no
such use. This code can be retrieved from history if it's needed in the
future.
Change-Id: Ie47a8b4bb173cba1a06bd3ca60391081987936b8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26625
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
It's constructor will now warn that it's deprecated and suggest using
ClockedObject directly. This change also gets rid of the params()
method and the Params typedef since they are functionally equivalent to
the ClockedObject versions.
It also removes the include of mem/port.hh which is not used in
mem_object.hh. This may break code which purposefully or (more likely)
accidentally depended on that transitive include from mem_object.hh.
Change-Id: I6dab3ba626e3f3ab6a6bd86edcf4f5cb4d6d2c45
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20720
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The idea of a "secure" memory area/access is specific to ARM and
shouldn't be in the common mem directory, although it's built in to the
generic memory protocol at this point.
Regardless, it should minimially be in its own file like the virtual
and physical port proxy classes are.
Change-Id: I140d4566ee2deded784adb04bcf6f11755a85c0c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18569
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This is the implementation of QoS algorithms support for gem5 memory
objects. This change-list provides a framework for specifying QoS
algorithm which can be used to prioritise service to specific masters in
the memory controller.
The QoS support implemented here is designed to be extendable so that
new QoS algorithms can be easily plugged into the memory controller as
"QoS Policies".
Change-Id: I0b611f13fce54dd1dd444eb806f8e98afd248bd5
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/11970
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Add a memory system component that delays traffic. The base
functionality to delay packets is implemented in the abstract MemDelay
class. This class exposes three methods that control packet delays:
* delayReq(pkt)
* delayResp(pkt)
* delaySnoopResp(pkt)
These methods should be specialized to implement delays for specific
packet types.
The class SimpleMemDelay uses the MemDelay base class to implement
constant delays for read/write requests and responses.
The intention is that these classes can be used for rapid prototyping
of components that add a small fixed delay and the same throughput as
the interconnect. I.e., any buffering done in the base class will be
small and proportional to the introduced delay.
Change-Id: I158cb85f20e32bfdbcbfed66a785b4b2dd47b628
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nicholas Lindsey <nicholas.lindsay@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/11521
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
The new version extracts all the x86 specific aspects of the class,
and builds the interface around a variable collection of template
arguments which are classes that represent the different levels of the
page table. The multilevel page table class is now much more ISA
independent.
Change-Id: Id42e168a78d0e70f80ab2438480cb6e00a3aa636
Reviewed-on: https://gem5-review.googlesource.com/7347
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>
This changeset adds a serial link model for the Hybrid Memory Cube (HMC).
SerialLink is a simple variation of the Bridge class, with the ability to
account for the latency of packet serialization. Also trySendTiming has been
modified to correctly model bandwidth.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This patch models a simple HMC Controller. It simply schedules the incoming
packets to HMC Serial Links using a round robin mechanism. This patch should
be applied in series with other patches modeling a complete HMC device.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This changeset moves the access trace functionality from the
CommMonitor into a separate probe. The probe can be hooked up to any
component that exports probe points of the type ProbePoints::Packet.
This patch moves the dependency on Google's Protocol Buffers library
from the CommMonitor to the MemTraceProbe, which means that the
CommMonitor (including stack distance profiling) no long depends on
it.
This changeset removes the stack distance calculator hooks from the
CommMonitor class and implements a stack distance calculator as a
memory system probe instead. The probe can be hooked up to any
component that exports probe points of the type ProbePoints::Packet.
This patch adds a stand-alone stack distance calculator. The stack
distance calculator is a passive SimObject that observes the addresses
passed to it. It calculates stack distances (LRU Distances) of
incoming addresses based on the partial sum hierarchy tree algorithm
described by Alamasi et al. http://doi.acm.org/10.1145/773039.773043.
For each transaction a hashtable look-up is performed. At every
non-unique transaction the tree is traversed from the leaf at the
returned index to the root, the old node is deleted from the tree, and
the sums (to the right) are collected and decremented. The collected
sum represets the stack distance of the found node. At every unique
transaction the stack distance is returned as
numeric_limits<uint64>::max().
In addition to the basic stack distance calculation, a feature to mark
an old node in the tree is added. This is useful if it is required to
see the reuse pattern. For example, Writebacks to the lower level
(e.g. membus from L2), can be marked instead of being removed from the
stack (isMarked flag of Node set to True). And then later if this same
address is accessed (by L1), the value of the isMarked flag would be
True. This gives some insight on how the Writeback policy of the
lower level affect the read/write accesses in an application.
Debugging is enabled by setting the verify flag to true. Debugging is
implemented using a dummy stack that behaves in a naive way, using STL
vectors. Note that this has a large impact on run time.
This patch adds the MemChecker and MemCheckerMonitor classes. While
MemChecker can be integrated anywhere in the system and is independent,
the most convenient usage is through the MemCheckerMonitor -- this
however, puts limitations on where the MemChecker is able to observe
read/write transactions.
This patch adds two MemoryObject's: ExternalMaster and ExternalSlave.
Each object has a single port which can be bound to an externally-
provided bridge to a port of another simulation system at
initialisation.
This patch adds a class to wrap DRAMPower Library in gem5.
This class initiates an object of class MemorySpecification
of the DRAMPower Library, passes the parameters from DRAMCtrl.py
to this object and creates an object of drampower library using
the memory specification.
This patch changes the name of the Bus classes to XBar to better
reflect the actual timing behaviour. The actual instances in the
config scripts are not renamed, and remain as e.g. iobus or membus.
As part of this renaming, the code has also been clean up slightly,
making use of range-based for loops and tidying up some comments. The
only changes outside the bus/crossbar code is due to the delay
variables in the packet.
--HG--
rename : src/mem/Bus.py => src/mem/XBar.py
rename : src/mem/coherent_bus.cc => src/mem/coherent_xbar.cc
rename : src/mem/coherent_bus.hh => src/mem/coherent_xbar.hh
rename : src/mem/noncoherent_bus.cc => src/mem/noncoherent_xbar.cc
rename : src/mem/noncoherent_bus.hh => src/mem/noncoherent_xbar.hh
rename : src/mem/bus.cc => src/mem/xbar.cc
rename : src/mem/bus.hh => src/mem/xbar.hh
This is a first cut at a simple snoop filter that tracks presence of lines in
the caches "above" it. The snoop filter can be applied at any given cache
hierarchy and will then handle the caches above it appropriately; there is no
need to use this only in the last-level bus.
This design currently has some limitations: missing stats, no notion of clean
evictions (these will not update the underlying snoop filter, because they are
not sent from the evicting cache down), no notion of capacity for the snoop
filter and thus no need for invalidations caused by capacity pressure in the
snoop filter. These are planned to be added on top with future change sets.
This patch enables the use of page tables that are stored in system memory
and respect x86 specification, in SE mode. It defines an architectural
page table for x86 as a MultiLevelPageTable class and puts a placeholder
class for other ISAs page tables, giving the possibility for future
implementation.
This patch adds a DRAMPower flag to enable off-line DRAM power
analysis using the DRAMPower tool. A new DRAMPower flag is added
and a follow-on patch adds a Python script to post-process the output
and order it based on time stamps.
The long-term goal is to link DRAMPower as a library and provide the
commands through function calls to the model rather than first
printing and then parsing the commands. At the moment it is also up to
the user to ensure that the same DRAM configuration is used by the
gem5 controller model and DRAMPower.
This patch adds power states to the controller. These states and the
transitions can be used together with the Micron power model. As a
more elaborate use-case, the transitions can be used to drive the
DRAMPower tool.
At the moment, the power-down modes are not used, and this patch
simply serves to capture the idle, auto refresh and active modes. The
patch adds a third state machine that interacts with the refresh state
machine.
