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docs/Getting-Started/Adding-An-Accelerator-Tutorial.rst
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Adding An Accelerator/Device
===============================
Accelerators or custom IO devices can be added to your SoC in several ways:
+ MMIO Peripheral (a.k.a TileLink-Attached Accelerator)
+ Tightly-Coupled RoCC Accelerator
These approaches differ in the method of the communication between the processor and the custom block.
* MMIO Peripheral (a.k.a TileLink-Attached Accelerator)
* Tightly-Coupled RoCC Accelerator
With the TileLink-Attached approach, the processor communicates with MMIO peripherals through memory-mapped registers.
These approaches differ in the method of the communication between the processor and the custom block.
In contrast, the processor communicates with a RoCC accelerators through a custom protocol and custom non-standard ISA instructions reserved in the RISC-V ISA encoding space. Each core can have up to four accelerators that are controlled by custom instructions and share resources with the CPU.
With the TileLink-Attached approach, the processor communicates with MMIO peripherals through memory-mapped registers.
In contrast, the processor communicates with a RoCC accelerators through a custom protocol and custom non-standard ISA instructions reserved in the RISC-V ISA encoding space.
Each core can have up to four accelerators that are controlled by custom instructions and share resources with the CPU.
RoCC coprocessor instructions have the following form.
::
.. code-block::
customX rd, rs1, rs2, funct
The X will be a number 0-3, and determines the opcode of the instruction,
which controls which accelerator an instruction will be routed to.
The ``rd``, ``rs1``, and ``rs2`` fields are the register numbers of the destination
register and two source registers. The ``funct`` field is a 7-bit integer that
the accelerator can use to distinguish different instructions from each other.
Note that communication through a RoCC interfaces requires a custom software toolchain, whereas MMIO peripherals can use that standard toolchain with approriate driver support.
The X will be a number 0-3, and determines the opcode of the instruction, which controls which accelerator an instruction will be routed to.
The ``rd``, ``rs1``, and ``rs2`` fields are the register numbers of the destination register and two source registers.
The ``funct`` field is a 7-bit integer that the accelerator can use to distinguish different instructions from each other.
Note that communication through a RoCC interface requires a custom software toolchain, whereas MMIO peripherals can use that standard toolchain with approriate driver support.
Integrating into the Generator Build System
-------------------------------------------
While developing, you want to include Chisel code in a submodule so that it
can be shared by different projects. To add a submodule to the project
template, make sure that your project is organized as follows.
While developing, you want to include Chisel code in a submodule so that it can be shared by different projects.
To add a submodule to the REBAR framework, make sure that your project is organized as follows.
.. code-block::
yourproject/
build.sbt
src/main/scala/
YourFile.scala
Put this in a git repository and make it accessible. Then add it as a submodule
to under the following directory hierarchy: ``rebar/generators/yourproject``.
Put this in a git repository and make it accessible.
Then add it as a submodule to under the following directory hierarchy: ``generators/yourproject``.
::
.. code-block:: shell
cd generators/
git submodule add https://git-repository.com/yourproject.git
Then add `yourproject` to the ReBAR top-level build.sbt file.
Then add ``yourproject`` to the REBAR top-level build.sbt file.
::
.. code-block:: scala
lazy val yourproject = project.settings(commonSettings).dependsOn(rocketchip)
You can then import the classes defined in the submodule in a new project if
you add it as a dependency. For instance, if you want to use this code in
the `example` project, change the final line in build.sbt to the following.
the ``example`` project, change the final line in build.sbt to the following.
::
.. code-block:: scala
lazy val example = (project in file(".")).settings(commonSettings).dependsOn(testchipip, yourproject)
Finally, add `yourproject` to the `PACKAGES` variable in the `Makefrag`. This will allow make to detect
that your source files have changed when building the verilog/firrtl files.
Finally, add ``yourproject`` to the ``PACKAGES`` variable in the ``common.mk`` file in the REBAR top level.
This will allow make to detect that your source files have changed when building the Verilog/FIRRTL files.
MMIO Peripheral
------------------
The easiest way to create a TileLink peripheral is to use the
TLRegisterRouter, which abstracts away the details of handling the TileLink
protocol and provides a convenient interface for specifying memory-mapped
registers. To create a RegisterRouter-based peripheral, you will need to
specify a parameter case class for the configuration settings, a bundle trait
with the extra top-level ports, and a module implementation containing the
actual RTL.
The easiest way to create a TileLink peripheral is to use the ``TLRegisterRouter``, which abstracts away the details of handling the TileLink protocol and provides a convenient interface for specifying memory-mapped registers.
To create a RegisterRouter-based peripheral, you will need to specify a parameter case class for the configuration settings, a bundle trait with the extra top-level ports, and a module implementation containing the actual RTL.
::
.. code-block:: scala
case class PWMParams(address: BigInt, beatBytes: Int)
trait PWMTLBundle extends Bundle {
@@ -103,16 +92,12 @@ actual RTL.
}
Once you have these classes, you can construct the final peripheral by
extending the TLRegisterRouter and passing the proper arguments. The first
set of arguments determines where the register router will be placed in the
global address map and what information will be put in its device tree entry.
The second set of arguments is the IO bundle constructor, which we create
by extending TLRegBundle with our bundle trait. The final set of arguments
is the module constructor, which we create by extends TLRegModule with our
module trait.
Once you have these classes, you can construct the final peripheral by extending the ``TLRegisterRouter`` and passing the proper arguments.
The first set of arguments determines where the register router will be placed in the global address map and what information will be put in its device tree entry.
The second set of arguments is the IO bundle constructor, which we create by extending ``TLRegBundle`` with our bundle trait.
The final set of arguments is the module constructor, which we create by extends ``TLRegModule`` with our module trait.
::
.. code-block:: scala
class PWMTL(c: PWMParams)(implicit p: Parameters)
extends TLRegisterRouter(
c.address, "pwm", Seq("ucbbar,pwm"),
@@ -120,20 +105,17 @@ module trait.
new TLRegBundle(c, _) with PWMTLBundle)(
new TLRegModule(c, _, _) with PWMTLModule)
The full module code can be found in ``generators/example/src/main/scala/PWM.scala``.
The full module code with comments can be found in src/main/scala/example/PWM.scala.
After creating the module, we need to hook it up to our SoC.
Rocket Chip accomplishes this using the cake pattern.
This basically involves placing code inside traits.
In the Rocket Chip cake, there are two kinds of traits: a ``LazyModule`` trait and a module implementation trait.
After creating the module, we need to hook it up to our SoC. Rocketchip
accomplishes this using the [cake pattern](http://www.cakesolutions.net/teamblogs/2011/12/19/cake-pattern-in-depth).
This basically involves placing code inside traits. In the RocketChip cake,
there are two kinds of traits: a LazyModule trait and a module implementation
trait.
The ``LazyModule`` trait runs setup code that must execute before all the hardware gets elaborated.
For a simple memory-mapped peripheral, this just involves connecting the peripheral's TileLink node to the MMIO crossbar.
The LazyModule trait runs setup code that must execute before all the hardware
gets elaborated. For a simple memory-mapped peripheral, this just involves
connecting the peripheral's TileLink node to the MMIO crossbar.
::
.. code-block:: scala
trait HasPeripheryPWM extends HasSystemNetworks {
implicit val p: Parameters
@@ -147,17 +129,15 @@ connecting the peripheral's TileLink node to the MMIO crossbar.
}
Note that the PWMTL class we created from the register router is itself a
LazyModule. Register routers have a TileLike node simply named "node", which
we can hook up to the RocketChip peripheryBus. This will automatically add
address map and device tree entries for the peripheral.
Note that the ``PWMTL`` class we created from the register router is itself a ``LazyModule``.
Register routers have a TileLike node simply named "node", which we can hook up to the Rocket Chip bus.
This will automatically add address map and device tree entries for the peripheral.
The module implementation trait is where we instantiate our PWM module and
connect it to the rest of the SoC. Since this module has an extra `pwmout`
output, we declare that in this trait, using Chisel's multi-IO
functionality. We then connect the PWMTL's pwmout to the pwmout we declared.
The module implementation trait is where we instantiate our PWM module and connect it to the rest of the SoC.
Since this module has an extra `pwmout` output, we declare that in this trait, using Chisel's multi-IO functionality.
We then connect the ``PWMTL``'s pwmout to the pwmout we declared.
::
.. code-block:: scala
trait HasPeripheryPWMModuleImp extends LazyMultiIOModuleImp {
implicit val p: Parameters
val outer: HasPeripheryPWM
@@ -167,11 +147,10 @@ functionality. We then connect the PWMTL's pwmout to the pwmout we declared.
pwmout := outer.pwm.module.io.pwmout
}
Now we want to mix our traits into the system as a whole.
This code is from ``generators/example/src/main/scala/Top.scala``.
Now we want to mix our traits into the system as a whole. This code is from
src/main/scala/example/Top.scala.
::
.. code-block:: scala
class ExampleTopWithPWM(q: Parameters) extends ExampleTop(q)
with PeripheryPWM {
override lazy val module = Module(
@@ -182,19 +161,15 @@ src/main/scala/example/Top.scala.
extends ExampleTopModule(l) with HasPeripheryPWMModuleImp
Just as we need separate traits for LazyModule and module implementation, we
need two classes to build the system. The ExampleTop classes already have the
basic peripherals included for us, so we will just extend those.
Just as we need separate traits for ``LazyModule`` and module implementation, we need two classes to build the system.
The ``ExampleTop`` classes already have the basic peripherals included for us, so we will just extend those.
The ExampleTop class includes the pre-elaboration code and also a lazy val to
produce the module implementation (hence LazyModule). The ExampleTopModule
class is the actual RTL that gets synthesized.
The ``ExampleTop`` class includes the pre-elaboration code and also a ``lazy val`` to produce the module implementation (hence ``LazyModule``).
The ``ExampleTopModule`` class is the actual RTL that gets synthesized.
Finally, we need to add a configuration class in
src/main/scala/example/Configs.scala that tells the TestHarness to instantiate
ExampleTopWithPWM instead of the default ExampleTop.
Finally, we need to add a configuration class in ``generators/example/src/main/scala/Configs.scala`` that tells the ``TestHarness`` to instantiate ``ExampleTopWithPWM`` instead of the default ``ExampleTop``.
::
.. code-block:: scala
class WithPWM extends Config((site, here, up) => {
case BuildTop => (p: Parameters) =>
Module(LazyModule(new ExampleTopWithPWM()(p)).module)
@@ -203,9 +178,9 @@ ExampleTopWithPWM instead of the default ExampleTop.
class PWMConfig extends Config(new WithPWM ++ new BaseExampleConfig)
Now we can test that the PWM is working. The test program is in tests/pwm.c
Now we can test that the PWM is working. The test program is in ``tests/pwm.c``.
::
.. code-block:: c
#define PWM_PERIOD 0x2000
#define PWM_DUTY 0x2008
#define PWM_ENABLE 0x2010
@@ -230,29 +205,26 @@ Now we can test that the PWM is working. The test program is in tests/pwm.c
}
This just writes out to the registers we defined earlier. The base of the
module's MMIO region is at 0x2000. This will be printed out in the address
map portion when you generated the verilog code.
This just writes out to the registers we defined earlier.
The base of the module's MMIO region is at 0x2000.
This will be printed out in the address map portion when you generated the verilog code.
Compiling this program with make produces a `pwm.riscv` executable.
Compiling this program with make produces a ``pwm.riscv`` executable.
Now with all of that done, we can go ahead and run our simulation.
::
.. code-block:: shell
cd verisim
make CONFIG=PWMConfig
./simulator-example-PWMConfig ../tests/pwm.riscv
Adding a RoCC Accelerator
----------------------------
RoCC accelerators are lazy modules that extend the LazyRoCC class.
Their implementation should extends the LazyRoCCModule class.
RoCC accelerators are lazy modules that extend the ``LazyRoCC`` class.
Their implementation should extends the ``LazyRoCCModule`` class.
::
.. code-block:: scala
class CustomAccelerator(opcodes: OpcodeSet)
(implicit p: Parameters) extends LazyRoCC(opcodes) {
override lazy val module = new CustomAcceleratorModule(this)
@@ -277,34 +249,30 @@ Their implementation should extends the LazyRoCCModule class.
}
The ``opcodes`` parameter for ``LazyRoCC`` is
the set of custom opcodes that will map to this accelerator. More on this
in the next subsection.
The ``opcodes`` parameter for ``LazyRoCC`` is the set of custom opcodes that will map to this accelerator.
More on this in the next subsection.
The ``LazyRoCC`` class contains two TLOutputNode instances, ``atlNode`` and ``tlNode``.
The former connects into a tile-local arbiter along with the backside of the
L1 instruction cache. The latter connects directly to the L1-L2 crossbar.
The corresponding Tilelink ports in the module implementation's IO bundle
are ``atl`` and ``tl``, respectively.
The former connects into a tile-local arbiter along with the backside of the L1 instruction cache.
The latter connects directly to the L1-L2 crossbar.
The corresponding Tilelink ports in the module implementation's IO bundle are ``atl`` and ``tl``, respectively.
The other interfaces available to the accelerator are ``mem``, which provides
access to the L1 cache; ``ptw`` which provides access to the page-table walker;
the ``busy`` signal, which indicates when the accelerator is still handling an
instruction; and the ``interrupt`` signal, which can be used to interrupt the CPU.
The other interfaces available to the accelerator are ``mem``, which provides access to the L1 cache;
``ptw`` which provides access to the page-table walker;
the ``busy`` signal, which indicates when the accelerator is still handling an instruction;
and the ``interrupt`` signal, which can be used to interrupt the CPU.
Look at the examples in rocket-chip/src/main/scala/tile/LazyRocc.scala for
detailed information on the different IOs.
Look at the examples in ``generators/rocket-chip/src/main/scala/tile/LazyRocc.scala`` for detailed information on the different IOs.
### Adding RoCC accelerator to Config
Adding RoCC accelerator to Config
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
RoCC accelerators can be added to a core by overriding the ``BuildRoCC`` parameter
in the configuration. This takes a sequence of functions producing ``LazyRoCC``
objects, one for each accelerator you wish to add.
RoCC accelerators can be added to a core by overriding the ``BuildRoCC`` parameter in the configuration.
This takes a sequence of functions producing ``LazyRoCC`` objects, one for each accelerator you wish to add.
For instance, if we wanted to add the previously defined accelerator and
route custom0 and custom1 instructions to it, we could do the following.
For instance, if we wanted to add the previously defined accelerator and route custom0 and custom1 instructions to it, we could do the following.
::
.. code-block:: scala
class WithCustomAccelerator extends Config((site, here, up) => {
case BuildRoCC => Seq((p: Parameters) => LazyModule(
new CustomAccelerator(OpcodeSet.custom0 | OpcodeSet.custom1)(p)))
@@ -313,17 +281,13 @@ route custom0 and custom1 instructions to it, we could do the following.
class CustomAcceleratorConfig extends Config(
new WithCustomAccelerator ++ new DefaultExampleConfig)
Adding a DMA port
-------------------
IO devices or accelerators (like a disk or network
driver), we may want to have the device write directly to the coherent
memory system instead. To add a device like that, you would do the following.
IO devices or accelerators (like a disk or network driver), we may want to have the device write directly to the coherent memory system instead.
To add a device like that, you would do the following.
::
.. code-block:: scala
class DMADevice(implicit p: Parameters) extends LazyModule {
val node = TLClientNode(TLClientParameters(
name = "dma-device", sourceId = IdRange(0, 1)))
@@ -355,8 +319,6 @@ memory system instead. To add a device like that, you would do the following.
The ``ExtBundle`` contains the signals we connect off-chip that we get data from.
The DMADevice also has a Tilelink client port that we connect into the L1-L2
crossbar through the front-side buffer (fsb). The sourceId variable given in
the TLClientNode instantiation determines the range of ids that can be used
in acquire messages from this device. Since we specified [0, 1) as our range,
only the ID 0 can be used.
The DMADevice also has a Tilelink client port that we connect into the L1-L2 crossbar through the front-side buffer (fsb).
The sourceId variable given in the ``TLClientNode`` instantiation determines the range of ids that can be used in acquire messages from this device.
Since we specified [0, 1) as our range, only the ID 0 can be used.

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Configs, Parameters, Mix-ins, and Everything In Between
========================================================
A significant portion of generators in the ReBAR framework use the Rocket chip parameter system.
A significant portion of generators in the REBAR framework use the Rocket Chip parameter system.
This parameter system enables for the flexible configuration of the SoC without invasive RTL changes.
In order to use the parameter system correctly, we will use several terms and conventions:
Parameter
Parameters
--------------------
TODO: Need to explain up, site, field, and other stuff from Henry's thesis.
It is important to note that a significant challenge with the Rocket parameter system is being able to identify the correct parameter to use, and the impact that parameter has on the overall system. We are still investigating methods to facilitate parameter exploration and discovery.
It is important to note that a significant challenge with the Rocket parameter system is being able to identify the correct parameter to use, and the impact that parameter has on the overall system.
We are still investigating methods to facilitate parameter exploration and discovery.
Config
Configs
---------------------
A `Config` is a collection of multiple parameters being set to specific values.
Configs are additive, and can override each other.
A Config can be composed of other configs.
The naming convetion for an additive config is ``With<YourConfig>``, while the naming convention for a non-additive config will be ``<YourConfig>``.
Configs can take arguments which will in-turn set parameters in the specific configs.
Example config:
A *Config* is a collection of multiple generator parameters being set to specific values.
Configs are additive, can override each other, and can be composed of other Configs.
The naming convention for an additive Config is ``With<YourConfigName>``, while the naming convention for a non-additive Config will be ``<YourConfig>``.
Configs can take arguments which will in-turn set parameters in the design or reference other parameters in the design (see :ref:`Parameters`).
:numref:`basic-config-example` shows a basic additive Config class that takes in zero arguments and instead uses hardcoded values to set the RTL design parameters.
In this example, ``MyAcceleratorConfig`` is a Scala case class that defines a set of variables that the generator can use when referencing the ``MyAcceleratorKey`` in the design.
.. _basic-config-example:
.. code-block:: scala
class WithMyAcceleratorParams extends Config((site, here, up) => {
case BusWidthBits => 128
case MyAcceleratorKey =>
MyAcceleratorConfig(
Rows = 2,
rows = 2,
rowBits = 64,
Columns = 16,
columns = 16,
hartId = 1,
some_length = 256,
)
someLength = 256)
})
Example config which uses a higher level config:
This next example (:numref:`complex-config-example`) shows a "higher-level" additive Config that uses prior parameters that were set to derive other parameters.
.. _complex-config-example:
.. code-block:: scala
class WithMyMoreComplexAcceleratorConfig extends Config((site, here, up) => {
case BusWidthBits => 128
case MyAcceleratorKey =>
MyAcceleratorConfig(
Rows = 2,
rowBits = site(SystemBusKey).beatBits,
hartId = up(RocketTilesKey, site).length,
)
hartId = up(RocketTilesKey, site).length)
})
Example of additive configs:
:numref:`top-level-config` shows a non-additive Config that combines the prior two additive Configs using ``++``.
The additive Configs are applied from the right to left in the list (or bottom to top in the example).
Thus, the order of the parameters being set will first start with the ``DefaultExampleConfig``, then ``WithMyAcceleratorParams``, then ``WithMyMoreComplexAcceleratorConfig``.
.. _top-level-config:
.. code-block:: scala
class SomeAdditiveConfig extends Config(
@@ -58,13 +65,15 @@ Example of additive configs:
new DefaultExampleConfig
)
Cake Pattern
-------------------------
The cake pattern is a scala programming pattern, which enable "mixing" of multiple traits or interface definitions (sometimes refered to as dependancy injection). It is used in the Rocket chip SoC library and ReBAR framework in merging multiple system components and IO interfaces into a large system component.
Example of using the cake pattern to merge multiple system components into a single top-level design, extending a basic Rocket SoC:
A cake pattern is a Scala programming pattern, which enable "mixing" of multiple traits or interface definitions (sometimes referred to as dependency injection).
It is used in the Rocket Chip SoC library and REBAR framework in merging multiple system components and IO interfaces into a large system component.
:numref:`cake-example` shows a Rocket Chip based SoC that merges multiple system components (BootROM, UART, etc) into a single top-level design.
.. _cake-example:
.. code-block:: scala
class MySoC(implicit p: Parameters) extends RocketSubsystem
@@ -78,9 +87,14 @@ Example of using the cake pattern to merge multiple system components into a sin
//Additional top-level specific instantiations or wiring
}
Mix-in
---------------------------
A mix-in is a scala trait, which sets parameters for specific system components, as well as enabling instantiation and wiring of the relevant system components to system buses.
The naming convetion for an additive mix-in is ``Has<YourMixin>``.
A mix-in is a Scala trait, which sets parameters for specific system components, as well as enabling instantiation and wiring of the relevant system components to system buses.
The naming convention for an additive mix-in is ``Has<YourMixin>``.
This is show in :numref:`cake-example` where things such as ``HasPeripherySerial`` connect a RTL component to a bus and expose signals to the top-level.
Additional References
---------------------------
A brief explanation of some of these topics is given in the following video: https://www.youtube.com/watch?v=Eko86PGEoDY.

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Development Ecosystem
===============================
REBAR Approach
-------------------------------------------
The trend towards agile hardware design and evaluation provides an ecosystem of debugging and implementation tools, that make it easier for computer architecture researchers to develop novel concepts.
REBAR hopes to build on this prior work in order to create a singular location to which multiple projects within the `Berkeley Architecture Research <https://bar.eecs.berkeley.edu/index.html>`__ can coexist and be used together.
REBAR aims to be the "one-stop shop" for creating and testing your own unique System on a Chip (SoC).
Chisel/FIRRTL
-------------------------------------------
One of the tools to help create new RTL designs quickly is the `Chisel Hardware Construction Language <https://chisel.eecs.berkeley.edu/>`__ and the `FIRRTL Compiler <https://freechipsproject.github.io/firrtl/>`__.
Chisel is an embedded language within Scala that provides a set of libraries to help hardware designers create highly parameterizable RTL.
FIRRTL on the other hand is a compiler for hardware which allows the user to run FIRRTL passes that can do dead code elimation, circuit analysis, connectivity checks, and much more!
These two tools in combination allow quick design space exploration and development of new RTL.
Generators
-------------------------------------------
Within this repository, all of the Chisel RTL is written as generators.
Generators are parametrized programs designed to generate RTL code based on configuration specifications.
Generators can be used to generate Systems-on-Chip (SoCs) using a collection of system components organized in unique generator projects.
Generators allow you to create a family of SoC designs instead of a single instance of a design!

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REBAR Basics
===============================
Generators
-------------------------------------------
The REBAR Framework currently consists of the following RTL generators:
Processor Cores
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**Rocket**
An in-order RISC-V core.
See :ref:`Rocket` for more information.
**BOOM (Berkeley Out-of-Order Machine)**
An out-of-order RISC-V core.
See :ref:`Berkeley Out-of-Order Machine (BOOM)` for more information.
Data-Parallel Accelerators
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**Hwacha**
A decoupled vector architecture co-processor.
Hwacha currently implements a non-standard RISC-V extension, using a vector architecture programming model.
Hwacha integrates with a Rocket or BOOM core using the RoCC (Rocket Custom Co-processor) interface.
See :ref:`Hwacha` for more information.
System Components:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**icenet**
A Network Interface Controller (NIC) designed to achieve up to 200 Gbps.
**sifive-blocks**
System components implemented by SiFive and used by SiFive projects, designed to be integrated with the Rocket Chip generator.
These system and peripheral components include UART, SPI, JTAG, I2C, PWM, and other peripheral and interface devices.
**AWL (Analog Widget Library)**
Digital components required for integration with high speed serial links.
**testchipip**
A collection of utilities used for testing chips and interfacing them with larger test environments.
.. Fixed Function Accelerators:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TBD
Tools
-------------------------------------------
**Chisel**
A hardware description library embedded in Scala.
Chisel is used to write RTL generators using meta-programming, by embedding hardware generation primitives in the Scala programming language.
The Chisel compiler elaborates the generator into a FIRRTL output.
See :ref:`Chisel` for more information.
**FIRRTL**
An intermediate representation library for RTL description of digital designs.
FIRRTL is used as a formalized digital circuit representation between Chisel and Verilog.
FIRRTL enables digital circuits manipulation between Chisel elaboration and Verilog generation.
See :ref:`FIRRTL` for more information.
**Barstools**
A collection of common FIRRTL transformations used to manipulate a digital circuit without changing the generator source RTL.
See :ref:`Barstools` for more information.
Toolchains
-------------------------------------------
**riscv-tools**
A collection of software toolchains used to develop and execute software on the RISC-V ISA.
The include compiler and assembler toolchains, functional ISA simulator (spike), the Berkeley Boot Loader (BBL) and proxy kernel.
The riscv-tools repository was previously required to run any RISC-V software, however, many of the riscv-tools components have since been upstreamed to their respective open-source projects (Linux, GNU, etc.).
Nevertheless, for consistent versioning, as well as software design flexibility for custom hardware, we include the riscv-tools repository and installation in the REBAR framework.
**esp-tools**
A fork of riscv-tools, designed to work with the Hwacha non-standard RISC-V extension.
This fork can also be used as an example demonstrating how to add additional RoCC accelerators to the ISA-level simulation (Spike) and the higher-level software toolchain (GNU binutils, riscv-opcodes, etc.)
Sims
-------------------------------------------
**verisim (Verilator wrapper)**
Verilator is an open source Verilog simulator.
The ``verisim`` directory provides wrappers which construct Verilator-based simulators from relevant generated RTL, allowing for execution of test RISC-V programs on the simulator (including vcd waveform files).
See :ref:`Verilator` for more information.
**vsim (VCS wrapper)**
VCS is a proprietary Verilog simulator.
Assuming the user has valid VCS licenses and installations, the ``vsim`` directory provides wrappers which construct VCS-based simulators from relevant generated RTL, allowing for execution of test RISC-V programs on the simulator (including vcd/vpd waveform files).
See :ref:`VCS` for more information.
**FireSim**
FireSim is an open-source FPGA-accelerated simulation platform, using Amazon Web Services (AWS) EC2 F1 instances on the public cloud.
FireSim automatically transforms and instruments open-hardware designs into fast (10s-100s MHz), deterministic, FPGA-based simulators that enable productive pre-silicon verification and performance validation.
To model I/O, FireSim includes synthesizeable and timing-accurate models for standard interfaces like DRAM, Ethernet, UART, and others.
The use of the elastic public cloud enable FireSim to scale simulations up to thousands of nodes.
In order to use FireSim, the repository must be cloned and executed on AWS instances.
See :ref:`FireSim` for more information.
VLSI
-------------------------------------------
**HAMMER**
HAMMER is a VLSI flow designed to provide a layer of abstraction between general physical design concepts to vendor-specific EDA tool commands.
The HAMMER flow provide automated scripts which generate relevant tool commands based on a higher level description of physical design constraints.
The HAMMER flow also allows for re-use of process technology knowledge by enabling the construction of process-technology-specific plug-ins, which describe particular constraints relating to that process technology (obsolete standard cells, metal layer routing constraints, etc.).
The HAMMER flow requires access to proprietary EDA tools and process technology libraries.
See :ref:`HAMMER` for more information.

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ReBAR Basics
===============================
Generators
-------------------------------------------
Generators are parametrized programs written as RTL code, designed to generate verilog code based on configuration specifications.
Generators can be used to generate Systems-on-Chip (SoCs) using a collection of system components organized in unique generator projects.
The ReBAR Framework currently consists of the following generators:
Processor Cores
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**Rocket**
An in-order RISC-V core.
**BOOM (Berkeley Out-of-Order Machine)**
An out-of-order RISC-V core.
Data-Parallel Accelerators
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**Hwacha**
A decoupled vector architecture co-processor. Hwacha currently implements a non-standard RISC-V extension, using a vector architecture programming model.
Hwacha integrates with a Rocket or BOOM core using the RoCC (Rocket Custom Co-processor) interface
System Components:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**icenet**
A Network Interface Controller (NIC) designed to achieve up to 200 Gbps.
**sifive-blocks**
System components implemented by SiFive and used by SiFive projects, designed to be integrated with the Rocket chip generator. These system and peripheral components include UART, SPI, JTAG, I2C, PWM, and other peripheral and interface devices.
**AWL (Analog Widget Library)**
Digital components required for integration with high speed serial links.
**testchipip**
A collection of utilites used for testing chips and interfacing them with larger test environments.
Fixed Function Accelerators:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TBD
Tools
-------------------------------------------
**Chisel**
A hardware description library embedded in Scala. Chisel is used to write RTL generators using meta-programming, by emdedding hardware generation primitives in the Scala programming language. The Chisel compilter elaborate the generator into a FIRRTL output.
**FIRRTL**
An intermediate representation library for RTL description of digital designs. FIRRTL is used as a formalized digital circuit representation between Chisel and Verilog. FIRRTL enables digital circuits manipulation between Chisel elaboration and Verilog generation.
**BARSTOOLS**
A collection of common FIRRTL transformations used to manipulate a digital circuit without changing the generator source RTL.
Toolchains
-------------------------------------------
**riscv-tools**
A collection of software toolchains used to develope and execute software on the RISC-V ISA. The include compiler and assembler toolchains, functional ISA simulator (spike), the Berkeley Boot Loader (BBL) and proxy kernel. The riscv-tools repository was previously required to run any RISC-V software, however, many of the riscv-tools components have since been upstreamed to their respective open-source projects (Linux, GNU, etc.). Nevertheless, for consistent versioning, as well as software design flexibility for custom hardware, we include the riscv-tools repository and installation in the ReBAR framework.
**esp-tools**
A fork of riscv-tools, designed to work with the Hwacha non-standard RISC-V extension. This fork can also be used as an example demonstrating how to add additional RoCC accelerators to the ISA-level simulation (Spike) and the higher-level software toolchain (GNU binutils, riscv-opcodes, etc.)
Sims
-------------------------------------------
**verisim (Verilator wrapper)**
Verilator is an open source Verilog simulator. The verisim directory provides wrappers which construct verilator-based simulators from relevant generated RTL, allowing for execution of test RISC-V programs on the simulator (including vcd waveform files).
**vsim (VCS wrapper)**
VCS is a proprietary Verilog simulator. Assuming the user has valid VCS licenses and installations, the vsim directory provides wrappers which construct VCS-based simulators from relevant generated RTL, allowing for execution of test RISC-V programs on the simulator (including vcd/vpd waveform files).
**FireSim**
FireSim is an open-source FPGA-accelerated simulation platform, using Amazon Web Services (AWS) EC2 F1 instances on the public cloud. FireSim automatically transforms and instruments open-hardware designs into fast (10s-100s MHz), deterministic, FPGA-based simulators that enable productive pre-silicon verification and performance validation. To model I/O, FireSim includes synthesizeable and timing-accurate models for standard interfaces like DRAM, Ethernet, UART, and others. The use of the elastic public clound enable FireSim to scale simulations up to thousands of nodes. In order to use FireSim, the repository must be cloned and executed on AWS instances.
VLSI
-------------------------------------------
**HAMMER**
HAMMER is a VLSI flow designed to provide a layer of abstraction between general physical design concepts to vendor-specific EDA tool commands. The HAMMER flow provide automated scripts which generate relevant tool commands based on a higher level description of physical desing contraints. The HAMMER flow also allows for re-use of process technology knowledge by enabling the construction of process-technology-specific plug-ins, which describe particular contraints relating to that process technology (obsolete standard cells, metal layer routing contraints, etc.). The HAMMER flow requires access to proprietry EDA tools and process technology libraries.

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Running A Simulation
========================================================
ReBAR provides support and intergration for multiple simulation flows, for various user levels and requirments.
In the majority of cases during a digital design development process, simple software RTL. When more advanced full-system evaluation is required, with long running workloads, FPGA-accelerated simulation will then become a preferable solution.
REBAR provides support and integration for multiple simulation flows, for various user levels and requirements.
In the majority of cases during a digital design development process, simple software RTL simulation is needed.
When more advanced full-system evaluation is required, with long running workloads, FPGA-accelerated simulation will then become a preferable solution.
Software RTL Simulation
------------------------
The ReBAR framework provides wrappers for two common software RTL simulators: the open-source Verilator simulator. and the proprietry VCS simulator.The following instructions assume at least one of these simulators is installed.
The REBAR framework provides wrappers for two common software RTL simulators:
the open-source Verilator simulator and the proprietary VCS simulator.
For more information on either of these simulators, please refer to :ref:`Verilator` or :ref:`VCS`.
The following instructions assume at least one of these simulators is installed.
Verilator
Verilator/VCS Flows
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Verilator is an open-source RTL simulator. We run Verilator simulations from within the ``sims/verisim`` directory. Therefore, we will start by entering that directory:
Verilator is an open-source RTL simulator.
We run Verilator simulations from within the ``sims/verisim`` directory which provides the necessary ``Makefile`` to both install and run Verilator simulations.
On the other hand, VCS is a proprietary RTL simulator.
We run VCS simulations from within the ``sims/vsim`` directory.
Assuming VCS is already installed on the machine running simulations (and is found on our ``PATH``), then this guide is the same for both Verilator and VCS.
First, we will start by entering the Verilator or VCS directory:
.. code-block:: shell
cd sims/verisim
# Enter Verilator directory
cd sims/verisim
In order to construct the simulator with our custom design, we run the following command within the ``sims/verisim`` directory:
# OR
# Enter VCS directory
cd sims/vsim
In order to construct the simulator with our custom design, we run the following command within the simulator directory:
.. code-block:: shell
make TOP=<my_top_level_name> CONFIG=<my_config_name> SBT_PROJECT=<my_sbt_package_name> MODEL=<my_test_environment>
make SBT_PROJECT=... MODEL=... VLOG_MODEL=... MODEL_PACKAGE=... CONFIG=... CONFIG_PACKAGE=... GENERATOR_PACKAGE=... TB=... TOP=...
Where ``<my_top_level_name>`` is the class name of the top level design, ``<my_config_name>`` is the name of the class we create for our parameters configuration, ``<my_sbt_package_name>`` is the name of the sbt package the include both our top-level class and our config class, and ``<my_test_environment>`` is the name of the class which defines the test harness for our system.
The ``make`` command may have additional parameters (such as ``CONFIG_PACKAGE`` or ``MODEL_PACKAGE``) depending on the complexity of the design and integration with multiple sub-project repositories in the sbt-based build system.
Each of these make variables correspond to a particular part of the design/codebase and are needed so that the make system can correctly build and make a RTL simulation.
The ``SBT_PROJECT`` is the ``build.sbt`` project that holds all of the source files and that will be run during the RTL build.
The ``MODEL`` and ``VLOG_MODEL`` are the top-level class names of the design.
Normally, these are the same, but in some cases these can differ (if the Chisel class differs than what is emitted in the Verilog).
The ``MODEL_PACKAGE`` is the Scala package (in the Scala code that says ``package ...``) that holds the ``MODEL`` class.
The ``CONFIG`` is the name of the class used for the parameter Config while the ``CONFIG_PACKAGE`` is the Scala package it resides in.
The ``GENERATOR_PACKAGE`` is the Scala package that holds the Generator class that elaborates the design.
The ``TB`` is the name of the Verilog wrapper that connects the ``TestHarness`` to VCS/Verilator for simulation.
Finally, the ``TOP`` variable is used to distinguish between the top-level of the design and the ``TestHarness`` in our system.
For example, in the normal case, the ``MODEL`` variable specifies the ``TestHarness`` as the top-level of the design.
However, the true top-level design, the SoC being simulated, is pointed to by the ``TOP`` variable.
This separation allows the infrastructure to separate files based on the harness or the SoC top level.
Common configurations are package using a ``SUB_PROJECT`` make variable. There, in order to simulate a simple Rocket-based example system we can use:
Common configurations of all these variables are packaged using a ``SUB_PROJECT`` make variable.
Therefore, in order to simulate a simple Rocket-based example system we can use:
.. code-block:: shell
make SUB_PROJECT=example
make SUB_PROJECT=example
Alternatively, if we would like to simulate a simple BOOM-based example system we can use:
.. code-block:: shell
make SUB_PROJECT=exampleboom
make SUB_PROJECT=exampleboom
Once the simulator has been constructed, we would like to run RISC-V programs on it. In the `sims/verisim` directory, we will find an executable file called `TODO`. We run this executable with out target RISC-V program as a command line argument. For example:
Once the simulator has been constructed, we would like to run RISC-V programs on it.
In the simulation directory, we will find an executable file called ``<...>-<package>-<config>``.
We run this executable with our target RISC-V program as a command line argument in one of two ways.
One, we can directly call the simulator binary or use make to run the binary for us with extra simulation flags.
For example:
.. code-block:: shell
./simulator-<my_sbt_package_name>-<my_config_name> my_program_binary
# directly calling the simulation binary
./<...>-<package>-<config> my_program_binary
Alternatively, we can run a pre-packaged suite of RISC-V assembly tests, by adding the make target run-asm-tests. For example
# using make to do it
make SUB_PROJECT=example BINARY=my_program_binary run-binary
Alternatively, we can run a pre-packaged suite of RISC-V assembly or benchmark tests, by adding the make target ``run-asm-tests`` or ``run-bmark-tests``.
For example:
.. code-block:: shell
make run-asm-tests TOP=<my_top_level_name> CONFIG=<my_config_name> SBT_PROJECT=<my_sbt_package_name> MODEL=<my_test_environment>
or
.. code-block:: shell
make run-asm-tests SUB_PROJECT=example
VCS
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
VCS is a proprietry RTL simulator. This guide assumes that the VCS installation is found on our PATH. We run VCS simulations from within the ``sims/vsim`` directory. Therefore, we will start by entering the directory:
.. code-block:: shell
cd sims/vsim
In order to construct the simulator with our custom design, we run the following command within the ``sims/vsim`` directory:
.. code-block:: shell
make TOP=<my_top_level_name> CONFIG=<my_config_name> SBT_PROJECT=<my_sbt_package_name> MODEL=<my_test_environment>
Where ``<my_top_level_name>`` is the class name of the top level design, ``<my_config_name>`` is the name of the class we create for our parameters configuration, ``<my_sbt_package_name>`` is the name of the sbt package the include both our top-level class and our config class, and ``<my_test_environment>`` is the name of the class which defines the test harness for our system.
The ``make`` command my have additional parameters (such as ``CONFIG_PACKAGE`` or ``MODEL_PACKAGE``) depending on the complexity of the design and integration with multiple sub-project repositories in the sbt-based build system.
Common configurations are package using a ``SUB_PROJECT`` make variable. There, in order to simulate a simple Rocket-based example system we can use:
.. code-block:: shell
make SUB_PROJECT=example
Alternatively, if we would like to simulate a simple BOOM-based example system we can use:
.. code-block:: shell
make SUB_PROJECT=exampleboom
Once the simulator has been constructed, we would like to run RISC-V programs on it. In the ``sims/vsim`` directory, we will find an executable file called ``TODO``. We run this executable with out target RISC-V program as a command line argument. For example:
.. code-block:: shell
./simulator-<my_sbt_package_name>-<my_config_name> my_program_binary
Alternatively, we can run a pre-packaged suite of RISC-V assembly tests, by adding the make target run-asm-tests. For example
.. code-block:: shell
make run-asm-tests TOP=<my_top_level_name> CONFIG=<my_config_name> SBT_PROJECT=<my_sbt_package_name> MODEL=<my_test_environment>
or
.. code-block:: shell
make run-asm-tests SUB_PROJECT=example
make SUB_PROJECT=example run-asm-tests
make SUB_PROJECT=example run-bmark-tests
Note: You need to specify all the make variables once again to match what the build gave to run the assembly tests or the benchmarks or the binaries if you are using the make option.
FPGA Accelerated Simulation
---------------------------
FireSim enables simulations at 1000x-100000x the speed of standard software simulation. This is enabled using FPGA-acceleration on F1 instances of the AWS (Amazon Web Services) public cloud. There FireSim simulation require to be set-up on the AWS public cloud rather than on our local development machine.
FireSim enables simulations at 1000x-100000x the speed of standard software simulation.
This is enabled using FPGA-acceleration on F1 instances of the AWS (Amazon Web Services) public cloud.
Therefore FireSim simulation requires to be set-up on the AWS public cloud rather than on our local development machine.
To run an FPGA-accelerated simulation using FireSim, a we need to clone the ReBAR repository (or our fork of the ReBAR repository) to an AWS EC2, and follow the setup instructions specificied in the FireSim Initial Setup documentation page.
To run an FPGA-accelerated simulation using FireSim, a we need to clone the REBAR repository (or our fork of the REBAR repository) to an AWS EC2, and follow the setup instructions specificied in the FireSim Initial Setup documentation page.
After setting up the FireSim environment, we now need to generate a FireSim simulation around our selected digital design. We will work from within the ``sims/firesim`` directory.
After setting up the FireSim environment, we now need to generate a FireSim simulation around our selected digital design.
We will work from within the ``sims/firesim`` directory.
TODO: Continue from here

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.. _Getting Started:
Getting Started
================================
These guides will walk you through the basics of the ReBAR framework:
These guides will walk you through the basics of the REBAR framework:
- First, we will go over the different configurations avaliable.
@@ -15,8 +13,8 @@ Hit next to get started!
:maxdepth: 2
:caption: Getting Started:
ReBAR-Basics
Configs-Parameters-Mixins
REBAR-Basics
Configs-Parameters-Mixins
Adding-An-Accelerator-Tutorial
Running-A-Simulation
rebar-generator-mixins

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SoC Generator Config Mix-ins:
==============================
@@ -88,8 +86,8 @@ SiFive Blocks
- HasSPIProtocol
- HasSPIEndian
- HasSPILength
- HasSPICSMode
- HasPeripherySPIFlash
- HasSPICSMode
- HasPeripherySPIFlash
- HasPeripheryUART