Merge branch 'dev' into howie-docs

docs/Generators/Hwacha.rst

@@ -2,7 +2,14 @@ Hwacha
 ====================================
 
 The Hwacha project is developing a new vector architecture for future computer systems that are constrained in their power and energy consumption.
-Inspired by traditional vector machines from the 70s and 80s, and lessons learned from our previous vector-thread architectures Scale and Maven, we are bringing back elegant, performant, and energy-efficient aspects of vector processing to modern data-parallel architectures.
-We propose a new vector-fetch architectural paradigm, which focuses on the following aspects for higher performance, better energy efficiency, and lower complexity.
+The Hwacha project is inspired by traditional vector machines from the 70s and 80s, and lessons learned from our previous vector-thread architectures such as Scale and Maven
+The Hwacha project includes the Hwacha microarchitecture generator, as well as the ``XHwacha`` non-standard RISC-V extension. Hwacha does not implement the RISC-V standard vector extension proposal.
 
-For more information, please visit the `Hwacha website <http://hwacha.org/>`__.
+For more information on the Hwacha project, please visit the `Hwacha website <http://hwacha.org/>`__.
+
+To add the Hwacha vector unit to an SoC, you should add the ``hwacha.DefaultHwachaConfig`` config mixin to the SoC configurations. The Hwacha vector unit uses the RoCC port of a Rocket or BOOM `tile`, and by default connects to the memory system through the `System Bus` (i.e., directly to the L2 cache). 
+
+To change the configuration of the Hwacha vector unit, you can write a custom configuration to replace the ``DefaultHwachaConfig``. You can view the ``DefaultHwachaConfig`` under `generators/hwacha/src/main/scala/configs.scala <https://github.com/ucb-bar/hwacha/blob/master/src/main/scala/configs.scala>`__ to see the possible configuration parameters.
+ 
+Since Hwacha implements a non-standard RISC-V extension, it requires a unique software toolchain to be able to compile and asseble its vector instructions.
+To install the Hwacha toolchain, run the ``./scripts/build-toolchains.sh esp-tools`` command within the root Chipyard directory. This may take a while, and it will install the ``esp-tools-install`` directory within your Chipyard root directory. ``esp-tools`` is a fork of ``riscv-tools`` (formerly a collection of relevant software RISC-V tools) that was enhanced with additional non-standard vector instructions. However, due to the upstreaming of the equivalent RISC-V toolchains, ``esp-tools`` may not be up-to-date with the latest mainline version of the tools included in it.

docs/Generators/Rocket-Chip.rst

@@ -1,15 +1,15 @@
-RocketChip
-==========
+Rocket Chip
+===========
 
-RocketChip is an SoC generator developed at Berkeley and now supported by
-SiFive. Chipyard uses RocketChip as the basis for producing a RISC-V SoC.
+Rocket Chip generator is an SoC generator developed at Berkeley and now supported by
+SiFive. Chipyard uses the Rocket Chip generator as the basis for producing a RISC-V SoC.
 
-RocketChip is distinct from Rocket, the in-order RISC-V CPU generator.
-RocketChip includes many parts of the SoC besides the CPU. Though RocketChip
-uses Rocket CPUs by default, it can also be configured to use the BOOM
+`Rocket Chip` is distinct from `Rocket core`, the in-order RISC-V CPU generator.
+Rocket Chip includes many parts of the SoC besides the CPU. Though Rocket Chip
+uses Rocket core CPUs by default, it can also be configured to use the BOOM
 out-of-order core generator or some other custom CPU generator instead.
 
-A detailed diagram of a typical RocketChip system is shown below.
+A detailed diagram of a typical Rocket Chip system is shown below.
 
 .. image:: ../_static/images/rocketchip-diagram.png
 

docs/Generators/Rocket.rst

@@ -1,8 +1,9 @@
-Rocket
+Rocket Core
 ====================================
 
-`Rocket <https://github.com/freechipsproject/rocket-chip>`__ is a 5-stage in-order scalar core generator that is supported by `SiFive <https://www.sifive.com/>`__.
-It supports the open source RV64GC RISC-V instruction set and is written in the Chisel hardware construction language.
+`Rocket <https://github.com/freechipsproject/rocket-chip>`__ is a 5-stage in-order scalar processor core generator, originally developed at UC Berkeley and currently supported by `SiFive <https://www.sifive.com/>`__. The `Rocket core` is used as a component within the `Rocket Chip SoC generator`. A Rocket core combined with L1 caches (data and instruction caches) form a `Rocket tile`. The `Rocket tile` is the replicable component of the `Rocket Chip SoC generator`.
+
+The Rocket core supports the open-source RV64GC RISC-V instruction set and is written in the Chisel hardware construction language.
 It has an MMU that supports page-based virtual memory, a non-blocking data cache, and a front-end with branch prediction.
 Branch prediction is configurable and provided by a branch target buffer (BTB), branch history table (BHT), and a return address stack (RAS).
 For floating-point,  Rocket  makes  use  of  Berkeley’s  Chisel  implementations  of  floating-point  units.

docs/Generators/SHA3.rst

@@ -0,0 +1,80 @@
+SHA3 RoCC Accelerator
+===================================
+The SHA3 accelerator is a basic RoCC accelerator for the SHA3 hashing algorithm.
+We like using SHA3 in Chipyard tutorial content because it is a self-contained, simple
+example of integrating a custom accelerator into Chipyard.
+
+
+Introduction
+-----------------------------------
+Secure hashing algorithms represent a class of hashing functions that provide four attributes: ease
+of hash computation, inability to generate the message from the hash (one-way property), inability
+to change the message and not the hash (weakly collision free property), and inability to find
+two messages with the same hash (strongly collision free property). The National Institute of
+Standards and Technology (NIST) recently held a competition for a new algorithm to be added to
+its set of Secure Hashing Algorithms (SHA). In 2012 the winner was determined to be the Keccak
+hashing function and a rough specification for SHA3 was established. The algorithm operates on
+variable length messages with a sponge function, and thus alternates between absorbing chunks of
+the message into a set of state bits and permuting the state. The absorbing is a simple bitwise
+XOR while the permutation is a more complex function composed of several operations, χ, θ, ρ,
+π, ι, that all perform various bitwise operations, including rotations, parity calculations, XORs,
+etc. The Keccak hashing function is parameterized for different sizes of state and message chunks
+but for this accelerator we will only support the Keccak-256 variant with 1600 bits of state and
+1088 bit message chunks. A diagram of the SHA3 accelerator is shown below.
+
+.. image:: ../_static/images/sha3.png
+
+Technical Details
+------------------------------------
+The accelerator is designed around three sub-systems, an
+interface with the processor, an interface with memory, and
+the actual hashing computation system. The interface
+with the processor is designed using the ROCC interface for
+coprocessors integrating with the RISC-V Rocket/BOOM
+processor. It includes the ability to transfer two 64 bit
+words to the co-processor, the request for a return value,
+and a small field for the function requested. The accelerator
+receives these requests using a ready/valid interface. The
+ROCC instruction is parsed and the needed information is
+stored into a execution context. The execution context contains
+the memory address of the message being hashed, the memory address
+to store the resulting hash in, the length of the message, and
+several other control fields.
+
+Once the execution context is valid the memory subsystem
+then begins to fetch chunks of the message. The memory
+subsystem is fully decoupled from the other subsystems
+and maintains a single full round memory buffers.
+The accelerators memory interface can provide a
+maximum of one 64 bit word per cycle which corresponds
+to 17 requests needed to fill a buffer (the size is dictated by
+the SHA3 algorithm). Memory requests to fill these buffers
+are sent out as rapidly as the memory interface can handle,
+with a tag field set to allow the different memory buffers
+requests to be distinguished, as they may be returned out of
+order. Once the memory subsystem has filled a buffer the
+control unit absorbs the buffer into the execution
+context, at which point the execution context is free to
+begin permutation, and the memory buffer is free to send
+more memory requests.
+
+After the buffer is absorbed, the hashing computation
+subsystem begins the permutation operations. Once
+the message is fully hashed, the hash is written to memory
+with a simple state machine.
+
+
+Using a SHA3 Accelerator
+------------------------
+Since the SHA3 accelerator is designed as a RoCC accelerator,
+it can be mixed into a Rocket or BOOM core by overriding the
+BuildRoCC key. The configuration mixin is defined in the SHA3
+generator. An example configuration highlighting the use of
+this mixin is shown here:
+
+.. literalinclude:: ../../generators/example/src/main/scala/RocketConfigs.scala
+   :language: scala
+   :start-after: DOC include start: Sha3Rocket
+   :end-before: DOC include end: Sha3Rocket
+
+

docs/Generators/SiFive-Generators.rst

@@ -0,0 +1,45 @@
+SiFive Generators
+==================
+
+Chipyard includes several open-source generators developed and maintained by `SiFive <https://www.sifive.com/>`__. 
+These are currently organized within two submodules named ``sifive-blocks`` and ``sifive-cache``.
+
+Last-Level Cache Generator
+-----------------------------
+
+``sifive-cache`` includes last-level cache geneator. The Chipyard framework uses this last-level cache as an L2 cache. To use this L2 cache, you should add the ``freechips.rocketchip.subsystem.WithInclusiveCache`` mixin to your SoC configuration.
+To learn more about configuring this L2 cache, please refer to the :ref:`memory-hierarchy` section.
+
+
+Peripheral Devices
+-------------------
+``sifive-blocks`` includes multiple peripheral device generators, such as UART, SPI, PWM, JTAG, GPIO and more.
+
+These peripheral devices usually affect the memory map of the SoC, and its top-level IO as well.
+To integrate one of these devices in your SoC, you will need to define a custom mixin with the approriate address for the device using the Rocket Chip parameter system. As an example, for a GPIO device you could add the following mixin to set the GPIO address to ``0x10012000``. This address is the start address for the GPIO configuration registers. 
+
+.. literalinclude:: ../../generators/example/src/main/scala/ConfigMixins.scala
+    :language: scala
+    :start-after: DOC include start: WithGPIO
+    :end-before: DOC include end: WithGPIO
+
+Additionally, if the device requires top-level IOs, you will need to define a mixin to change the top-level configuration of your SoC.
+When adding a top-level IO, you should also be aware of whether it interacts with the test-harness.
+For example, a GPIO device would require a GPIO pin, and therefore we would write a mixin to augment the top level as follows:
+
+.. literalinclude:: ../../generators/example/src/main/scala/ConfigMixins.scala
+    :language: scala
+    :start-after: DOC include start: WithGPIOTop
+    :end-before: DOC include end: WithGPIOTop
+
+This example instantiates a top-level module with include GPIO ports (``TopWithGPIO``), and then ties-off the GPIO port inputs to 0 (``false.B``).
+
+
+Finally, you add the relevant config mixin to the SoC config. For example:
+
+.. literalinclude:: ../../generators/example/src/main/scala/RocketConfigs.scala
+    :language: scala
+    :start-after: DOC include start: GPIORocketConfig
+    :end-before: DOC include end: GPIORocketConfig
+
+Some of the devices in ``sifive-blocks`` (such as GPIO) may already have pre-defined mixins within the Chipyard example project. You may be able to use these config mixins directly, but you should be aware of their addresses within the SoC address map. 

docs/Generators/index.rst

@@ -1,19 +1,28 @@
+.. _generator-index:
+
 Generators
 ============================
 
-Generator can be thought of as a generalized RTL design, written using a mix of meta-programming and standard RTL.
+A Generator can be thought of as a generalized RTL design, written using a mix of meta-programming and standard RTL.
 This type of meta-programming is enabled by the Chisel hardware description language (see :ref:`Chisel`).
 A standard RTL design is essentially just a single instance of a design coming from a generator.
 However, by using meta-programming and parameter systems, generators can allow for integration of complex hardware designs in automated ways.
 The following pages introduce the generators integrated with the Chipyard framework.
 
+Chipyard bundles the source code for the generators, under the ``generators`` directory.
+It builds them from source each time (although the build system will cache results if they have not changed),
+so changes to the generators themselves will automatically be used when building with Chipyard and propagate to software simulation, FPGA-accelerated simulation, and VLSI flows.
+
+
 .. toctree::
    :maxdepth: 2
    :caption: Generators:
 
+   Rocket-Chip
    Rocket
    BOOM
    Hwacha
-   RocketChip
    IceNet
    TestChipIP
+   SiFive-Generators   
+   SHA3