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Merge pull request #34 from mithro/master 

More README fixes
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@ -54,12 +54,12 @@ There is a gitter channel for all questions about VexRiscv :<br>
For commercial support, please contact spinalhdl@gmail.com. For commercial support, please contact spinalhdl@gmail.com.
## Area usage and maximal frequency ## Area usage and maximal frequency
The following numbers were obtained by synthesizing the CPU as toplevel without any specific synthesis options to save area or to get better maximal frequency (neutral).<br> The following numbers were obtained by synthesizing the CPU as toplevel without any specific synthesis options to save area or to get better maximal frequency (neutral).<br>
The clock constraint is set to an unattainable value, which tends to increase the design area.<br> The clock constraint is set to an unattainable value, which tends to increase the design area.<br>
The dhrystone benchmark was compiled with the `-O3 -fno-inline` option.<br> The dhrystone benchmark was compiled with the `-O3 -fno-inline` option.<br>
All the cached configurations have some cache trashing during the dhrystone benchmark except the `VexRiscv full max perf` one. This of course reduces the performance. It is possible to produce All the cached configurations have some cache trashing during the dhrystone benchmark except the `VexRiscv full max perf` one. This of course reduces the performance. It is possible to produce
dhrystone binaries which fit inside a 4KB I$ and 4KB D$ (I already had this case once) but currently it isn't the case.<br> dhrystone binaries which fit inside a 4KB I$ and 4KB D$ (I already had this case once) but currently it isn't the case.<br>
The CPU configurations used below can be found in the `src/scala/vexriscv/demo` directory. The CPU configurations used below can be found in the `src/scala/vexriscv/demo` directory.
@ -67,54 +67,54 @@ The CPU configurations used below can be found in the `src/scala/vexriscv/demo`
VexRiscv smallest (RV32I, 0.52 DMIPS/Mhz, no datapath bypass, no interrupt) -> VexRiscv smallest (RV32I, 0.52 DMIPS/Mhz, no datapath bypass, no interrupt) ->
Artix 7 -> 346 Mhz 481 LUT 539 FF Artix 7 -> 346 Mhz 481 LUT 539 FF
Cyclone V -> 201 Mhz 347 ALMs Cyclone V -> 201 Mhz 347 ALMs
Cyclone IV -> 190 Mhz 673 LUT 529 FF Cyclone IV -> 190 Mhz 673 LUT 529 FF
iCE40 -> 81 Mhz 1130 LC iCE40 -> 81 Mhz 1130 LC
VexRiscv smallest (RV32I, 0.52 DMIPS/Mhz, no datapath bypass) -> VexRiscv smallest (RV32I, 0.52 DMIPS/Mhz, no datapath bypass) ->
Artix 7 -> 340 Mhz 562 LUT 589 FF Artix 7 -> 340 Mhz 562 LUT 589 FF
Cyclone V -> 202 Mhz 387 ALMs Cyclone V -> 202 Mhz 387 ALMs
Cyclone IV -> 180 Mhz 780 LUT 579 FF Cyclone IV -> 180 Mhz 780 LUT 579 FF
iCE40 -> 71 Mhz 1278 LC iCE40 -> 71 Mhz 1278 LC
VexRiscv small and productive (RV32I, 0.82 DMIPS/Mhz) -> VexRiscv small and productive (RV32I, 0.82 DMIPS/Mhz) ->
Artix 7 -> 327 Mhz 698 LUT 558 FF Artix 7 -> 327 Mhz 698 LUT 558 FF
Cyclone V -> 158 Mhz 524 ALMs Cyclone V -> 158 Mhz 524 ALMs
Cyclone IV -> 146 Mhz 1,061 LUT 552 FF Cyclone IV -> 146 Mhz 1,061 LUT 552 FF
iCE40 -> 55 Mhz 1541 LC iCE40 -> 55 Mhz 1541 LC
VexRiscv small and productive with I$ (RV32I, 0.72 DMIPS/Mhz, 4KB-I$) -> VexRiscv small and productive with I$ (RV32I, 0.72 DMIPS/Mhz, 4KB-I$) ->
Artix 7 -> 331 Mhz 727 LUT 600 FF Artix 7 -> 331 Mhz 727 LUT 600 FF
Cyclone V -> 152 Mhz 536 ALMs Cyclone V -> 152 Mhz 536 ALMs
Cyclone IV -> 156 Mhz 1,075 LUT 565 FF Cyclone IV -> 156 Mhz 1,075 LUT 565 FF
iCE40 -> 54 Mhz 1686 LC iCE40 -> 54 Mhz 1686 LC
VexRiscv full no cache (RV32IM, 1.22 DMIPS/Mhz, single cycle barrel shifter, debug module, catch exceptions, static branch) -> VexRiscv full no cache (RV32IM, 1.22 DMIPS/Mhz, single cycle barrel shifter, debug module, catch exceptions, static branch) ->
Artix 7 -> 295 Mhz 1399 LUT 971 FF Artix 7 -> 295 Mhz 1399 LUT 971 FF
Cyclone V -> 151 Mhz 922 ALMs Cyclone V -> 151 Mhz 922 ALMs
Cyclone IV -> 136 Mhz 1,859 LUT 992 FF Cyclone IV -> 136 Mhz 1,859 LUT 992 FF
VexRiscv full (RV32IM, 1.21 DMIPS/Mhz with cache trashing, 4KB-I$,4KB-D$, single cycle barrel shifter, debug module, catch exceptions, static branch) -> VexRiscv full (RV32IM, 1.21 DMIPS/Mhz with cache trashing, 4KB-I$,4KB-D$, single cycle barrel shifter, debug module, catch exceptions, static branch) ->
Artix 7 -> 253 Mhz 1840 LUT 1394 FF Artix 7 -> 253 Mhz 1840 LUT 1394 FF
Cyclone V -> 126 Mhz 1,172 ALMs Cyclone V -> 126 Mhz 1,172 ALMs
Cyclone IV -> 117 Mhz 2,548 LUT 1,703 FF Cyclone IV -> 117 Mhz 2,548 LUT 1,703 FF
VexRiscv full max perf -> (RV32IM, 1.44 DMIPS/Mhz, 16KB-I$,16KB-D$, single cycle barrel shifter, debug module, catch exceptions, dynamic branch prediction in the fetch stage, branch and shift operations done in the Execute stage) -> VexRiscv full max perf -> (RV32IM, 1.44 DMIPS/Mhz, 16KB-I$,16KB-D$, single cycle barrel shifter, debug module, catch exceptions, dynamic branch prediction in the fetch stage, branch and shift operations done in the Execute stage) ->
Artix 7 -> 183 Mhz 1813 LUT 1424 FF Artix 7 -> 183 Mhz 1813 LUT 1424 FF
Cyclone V -> 93 Mhz 1,253 ALMs Cyclone V -> 93 Mhz 1,253 ALMs
Cyclone IV -> 84 Mhz 2,642 LUT 1,711 FF Cyclone IV -> 84 Mhz 2,642 LUT 1,711 FF
VexRiscv full with MMU (RV32IM, 1.26 DMIPS/Mhz with cache trashing, 4KB-I$, 4KB-D$, single cycle barrel shifter, debug module, catch exceptions, dynamic branch, MMU) -> VexRiscv full with MMU (RV32IM, 1.26 DMIPS/Mhz with cache trashing, 4KB-I$, 4KB-D$, single cycle barrel shifter, debug module, catch exceptions, dynamic branch, MMU) ->
Artix 7 -> 214 Mhz 2070 LUT 1913 FF Artix 7 -> 214 Mhz 2070 LUT 1913 FF
Cyclone V -> 108 Mhz 1,430 ALMs Cyclone V -> 108 Mhz 1,430 ALMs
Cyclone IV -> 100 Mhz 2,976 LUT 2,201 FF Cyclone IV -> 100 Mhz 2,976 LUT 2,201 FF
``` ```
The following configuration results in 1.44 DMIPS/MHz: The following configuration results in 1.44 DMIPS/MHz:
- 5 stage : F -> D -> E -> M -> WB - 5 stage : F -> D -> E -> M -> WB
- single cycle ADD/SUB/Bitwise/Shift ALU - single cycle ADD/SUB/Bitwise/Shift ALU
- branch/jump done in the E stage - branch/jump done in the E stage
- memory load values are bypassed in the WB stage (late result) - memory load values are bypassed in the WB stage (late result)
- 33 cycle division with bypassing in the M stage (late result) - 33 cycle division with bypassing in the M stage (late result)
- single cycle multiplication with bypassing in the WB stage (late result) - single cycle multiplication with bypassing in the WB stage (late result)
- dynamic branch prediction done in the F stage with a direct mapped target buffer cache (no penalties on correct predictions) - dynamic branch prediction done in the F stage with a direct mapped target buffer cache (no penalties on correct predictions)
@ -156,7 +156,7 @@ You can find two example CPU instances in:
- src/main/scala/vexriscv/GenFull.scala - src/main/scala/vexriscv/GenFull.scala
- src/main/scala/vexriscv/GenSmallest.scala - src/main/scala/vexriscv/GenSmallest.scala
To generate the corresponding RTL as a VexRiscv.v file, run: To generate the corresponding RTL as a VexRiscv.v file, run:
```sh ```sh
sbt "run-main vexriscv.demo.GenFull" sbt "run-main vexriscv.demo.GenFull"
@ -170,14 +170,14 @@ sbt "run-main vexriscv.demo.GenSmallest"
NOTES: NOTES:
- It could take time the first time you run it. - It could take time the first time you run it.
- The VexRiscv project may need an unreleased master-head of the SpinalHDL repo. If it fails to compile, just get the SpinalHDL repository and - The VexRiscv project may need an unreleased master-head of the SpinalHDL repo. If it fails to compile, just get the SpinalHDL repository and
do a "sbt clean compile publish-local" in it as described in the dependencies chapter. do a "sbt clean compile publish-local" in it as described in the dependencies chapter.
## Regression tests ## Regression tests
To run tests (need the verilator simulator), go in the src/test/cpp/regression folder and run : To run tests (need the verilator simulator), go in the src/test/cpp/regression folder and run :
```sh ```sh
# To test the GenFull CPU # To test the GenFull CPU
# (Don't worry about the CSR test not passing, basicaly the GenFull isn't the truly full version of the CPU, some CSR features are disable in it) # (Don't worry about the CSR test not passing, basicaly the GenFull isn't the truly full version of the CPU, some CSR features are disable in it)
make clean run make clean run
@ -243,7 +243,7 @@ See https://drive.google.com/drive/folders/1a7FyMOYgFc9UDhfsWUSCjyqDCvOrts2J?usp
## Briey SoC ## Briey SoC
As a demonstrator, a SoC named Briey is implemented in `src/main/scala/vexriscv/demo/Briey.scala`. This SoC is very similar to As a demonstrator, a SoC named Briey is implemented in `src/main/scala/vexriscv/demo/Briey.scala`. This SoC is very similar to
the [Pinsec SOC](https://spinalhdl.github.io/SpinalDoc/spinal/lib/pinsec/hardware/): the [Pinsec SOC](https://spinalhdl.github.io/SpinalDoc/spinal/lib/pinsec/hardware/):
![Alt text](assets/brieySoc.png?raw=true "") ![Alt text](assets/brieySoc.png?raw=true "")
@ -276,10 +276,10 @@ You can find multiple software examples and demos here: https://github.com/Spina
You can find some FPGA projects which instantiate the Briey SoC here (DE1-SoC, DE0-Nano): https://drive.google.com/drive/folders/0B-CqLXDTaMbKZGdJZlZ5THAxRTQ?usp=sharing You can find some FPGA projects which instantiate the Briey SoC here (DE1-SoC, DE0-Nano): https://drive.google.com/drive/folders/0B-CqLXDTaMbKZGdJZlZ5THAxRTQ?usp=sharing
Here are some measurements of Briey SoC timings and area : Here are some measurements of Briey SoC timings and area :
``` ```
Artix 7 -> 239 Mhz 3227 LUT 3410 FF Artix 7 -> 239 Mhz 3227 LUT 3410 FF
Cyclone V -> 125 Mhz 2,207 ALMs Cyclone V -> 125 Mhz 2,207 ALMs
Cyclone IV -> 112 Mhz 4,594 LUT 3,620 Cyclone IV -> 112 Mhz 4,594 LUT 3,620
``` ```
@ -308,11 +308,14 @@ To generate the Murax SoC Hardware :
# To generate the SoC without any content in the ram # To generate the SoC without any content in the ram
sbt "run-main vexriscv.demo.Murax" sbt "run-main vexriscv.demo.Murax"
# To generate the SoC with a demo program in the SoC # To generate the SoC with a demo program already in ram
# Will blink led and echo UART RX to UART TX (in the verilator sim, type some text and press enter to send UART frames to the Murax RX pin)
sbt "run-main vexriscv.demo.MuraxWithRamInit" sbt "run-main vexriscv.demo.MuraxWithRamInit"
``` ```
The demo program included by default with `MuraxWithRamInit` will blink the
LEDs and echo characters received on the UART back to the user. To see this
when running the Verilator sim, type some text and press enter.
Then go in src/test/cpp/murax and run the simulation with : Then go in src/test/cpp/murax and run the simulation with :
```sh ```sh
@ -331,15 +334,15 @@ Here are some timing and area measurements of the Murax SoC:
``` ```
Murax interlocked stages (0.45 DMIPS/Mhz) -> Murax interlocked stages (0.45 DMIPS/Mhz) ->
Artix 7 -> 305 Mhz 1004 LUT 1297 FF Artix 7 -> 305 Mhz 1004 LUT 1297 FF
Cyclone V -> 160 Mhz 744 ALMs Cyclone V -> 160 Mhz 744 ALMs
Cyclone IV -> 148 Mhz 1,522 LUT 1,255 FF Cyclone IV -> 148 Mhz 1,522 LUT 1,255 FF
ICE40-HX -> 51 Mhz 2402 LC (icestorm) ICE40-HX -> 51 Mhz 2402 LC (icestorm)
MuraxFast bypassed stages (0.65 DMIPS/Mhz) -> MuraxFast bypassed stages (0.65 DMIPS/Mhz) ->
Artix 7 -> 312 Mhz 1240 LUT 1330 FF Artix 7 -> 312 Mhz 1240 LUT 1330 FF
Cyclone V -> 159 Mhz 884 ALMs Cyclone V -> 159 Mhz 884 ALMs
Cyclone IV -> 142 Mhz 1,755 LUT 1,289 FF Cyclone IV -> 142 Mhz 1,755 LUT 1,289 FF
ICE40-HX -> 50 Mhz, 2787 LC (icestorm) ICE40-HX -> 50 Mhz, 2787 LC (icestorm)
``` ```
@ -347,7 +350,7 @@ Some scripts to generate the SoC and call the icestorm toolchain can be found he
A toplevel simulation testbench with the same features + a GUI are implemented with SpinalSim. You can find it in `src/test/scala/vexriscv/MuraxSim.scala`. A toplevel simulation testbench with the same features + a GUI are implemented with SpinalSim. You can find it in `src/test/scala/vexriscv/MuraxSim.scala`.
To run it : To run it :
```sh ```sh
# This will generate the Murax RTL + run its testbench. You need Verilator 3.9xx installated. # This will generate the Murax RTL + run its testbench. You need Verilator 3.9xx installated.
@ -367,7 +370,7 @@ wget https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-20171231-x8
tar -xzvf riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6.tar.gz tar -xzvf riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6.tar.gz
sudo mv riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6 /opt/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6 sudo mv riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6 /opt/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6
sudo mv /opt/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6 /opt/riscv sudo mv /opt/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6 /opt/riscv
echo 'export PATH=/opt/riscv/bin:$PATH' >> ~/.bashrc echo 'export PATH=/opt/riscv/bin:$PATH' >> ~/.bashrc
``` ```
If you want to compile the rv32i and rv32im GCC toolchain from source code and install them in `/opt/`, do the following (will take one hour): If you want to compile the rv32i and rv32im GCC toolchain from source code and install them in `/opt/`, do the following (will take one hour):
@ -401,7 +404,7 @@ echo -e "\\nRISC-V Toolchain installation completed!"
## CPU parametrization and instantiation example ## CPU parametrization and instantiation example
You can find many examples of different configurations in the https://github.com/SpinalHDL/VexRiscv/tree/master/src/main/scala/vexriscv/demo folder. You can find many examples of different configurations in the https://github.com/SpinalHDL/VexRiscv/tree/master/src/main/scala/vexriscv/demo folder.
Here is one such example: Here is one such example:
@ -551,7 +554,7 @@ This example is a very simple one, but each plugin can really have access to the
- Provide an alternative implementation - Provide an alternative implementation
- ... - ...
As a demonstrator, this SimdAddPlugin was integrated in the `src/main/scala/vexriscv/demo/GenCustomSimdAdd.scala` CPU configuration As a demonstrator, this SimdAddPlugin was integrated in the `src/main/scala/vexriscv/demo/GenCustomSimdAdd.scala` CPU configuration
and is self-tested by the `src/test/cpp/custom/simd_add` application by running the following commands : and is self-tested by the `src/test/cpp/custom/simd_add` application by running the following commands :
```sh ```sh
@ -570,7 +573,7 @@ To retrieve the plugin related signals in your waveform viewer, just filter with
## Adding a new CSR via the plugin system ## Adding a new CSR via the plugin system
Here are two examples about how to add a custom CSR to the CPU via the plugin system: Here are two examples about how to add a custom CSR to the CPU via the plugin system:
https://github.com/SpinalHDL/VexRiscv/blob/master/src/main/scala/vexriscv/demo/CustomCsrDemoPlugin.scala https://github.com/SpinalHDL/VexRiscv/blob/master/src/main/scala/vexriscv/demo/CustomCsrDemoPlugin.scala
The first one (`CustomCsrDemoPlugin`) adds an instruction counter and a clock cycle counter into the CSR mapping (and also do tricky stuff as a demonstration). The first one (`CustomCsrDemoPlugin`) adds an instruction counter and a clock cycle counter into the CSR mapping (and also do tricky stuff as a demonstration).
@ -606,8 +609,8 @@ toplevelReset >----+--------> debugReset |
## VexRiscv Architecture ## VexRiscv Architecture
VexRiscv is implemented via a 5 stage in-order pipeline on which many optional and complementary plugins add functionalities to provide a functional RISC-V CPU. VexRiscv is implemented via a 5 stage in-order pipeline on which many optional and complementary plugins add functionalities to provide a functional RISC-V CPU.
This approach is completely unconventional and only possible through meta hardware description languages (SpinalHDL in the current case) but has proven its advantages This approach is completely unconventional and only possible through meta hardware description languages (SpinalHDL in the current case) but has proven its advantages
via the VexRiscv implementation: via the VexRiscv implementation:
- You can swap/turn on/turn off parts of the CPU directly via the plugin system - You can swap/turn on/turn off parts of the CPU directly via the plugin system
@ -615,7 +618,7 @@ via the VexRiscv implementation:
- It allows the CPU configuration to cover a very large spectrum of implementation without cooking spaghetti code - It allows the CPU configuration to cover a very large spectrum of implementation without cooking spaghetti code
- It allows your code base to truly produce a parametrized CPU design - It allows your code base to truly produce a parametrized CPU design
If you generate the CPU without any plugin, it will only contain the definition of the 5 pipeline stages and their basic arbitration, but nothing else, If you generate the CPU without any plugin, it will only contain the definition of the 5 pipeline stages and their basic arbitration, but nothing else,
as everything else, including the program counter is added into the CPU via plugins. as everything else, including the program counter is added into the CPU via plugins.
### Plugins ### Plugins
@ -650,11 +653,11 @@ This plugin implements the program counter and a jump service to all plugins.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| resetVector | BigInt | Address of the program counter after the reset | | resetVector | BigInt | Address of the program counter after the reset |
| relaxedPcCalculation | Boolean | By default, jumps have an asynchronous immediate effect on the program counter, which reduces the branch penalty by one cycle but could reduce the FMax as it will combinatorialy drive the instruction bus address signal. To avoid this you can set this parameter to true, which will make the jump affecting the programm counter in a sequancial way, which will cut the combinatorial path but add one additional cycle of penalty when a jump occur. | | relaxedPcCalculation | Boolean | By default, jumps have an asynchronous immediate effect on the program counter, which reduces the branch penalty by one cycle but could reduce the FMax as it will combinatorialy drive the instruction bus address signal. To avoid this you can set this parameter to true, which will make the jump affecting the programm counter in a sequancial way, which will cut the combinatorial path but add one additional cycle of penalty when a jump occur. |
The jump interface implemented by this plugin allows all other plugins to request jumps. The stage argument specifies from which stage the jump is asked, The jump interface implemented by this plugin allows all other plugins to request jumps. The stage argument specifies from which stage the jump is asked,
which allows the PcManagerSimplePlugin plugin to manage priorities between jump requests. which allows the PcManagerSimplePlugin plugin to manage priorities between jump requests.
```scala ```scala
@ -670,11 +673,11 @@ This plugin operates on the prefetch stage.
This plugin fetches instructions via a very simple and neutral memory interface going outside the CPU. This plugin fetches instructions via a very simple and neutral memory interface going outside the CPU.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| interfaceKeepData | Boolean | Specifies if the read/response interface keeps the data until the next one, or if it's only present a single cycle.| | interfaceKeepData | Boolean | Specifies if the read/response interface keeps the data until the next one, or if it's only present a single cycle.|
| catchAccessFault | Boolean | When the read response specifies a read error and this parameter is true, it will generate a CPU exception trap | | catchAccessFault | Boolean | When the read response specifies a read error and this parameter is true, it will generate a CPU exception trap |
Here is the SimpleBus interface definition Here is the SimpleBus interface definition
```scala ```scala
case class IBusSimpleCmd() extends Bundle{ case class IBusSimpleCmd() extends Bundle{
@ -682,7 +685,7 @@ case class IBusSimpleCmd() extends Bundle{
} }
case class IBusSimpleRsp() extends Bundle with IMasterSlave{ case class IBusSimpleRsp() extends Bundle with IMasterSlave{
val ready = Bool val ready = Bool
val error = Bool val error = Bool
val inst = Bits(32 bits) val inst = Bits(32 bits)
@ -713,7 +716,7 @@ This plugin fits in the fetch stage.
Simple and light multi-way instruction cache. Simple and light multi-way instruction cache.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| cacheSize | Int | Total storage capacity of the cache | | cacheSize | Int | Total storage capacity of the cache |
| bytePerLine | Int | Number of bytes per cache line | | bytePerLine | Int | Number of bytes per cache line |
| wayCount | Int | Number of cache ways | | wayCount | Int | Number of cache ways |
@ -730,16 +733,16 @@ Note: If you enable the twoCycleRam option and if wayCount is bigger than one, t
#### DecoderSimplePlugin #### DecoderSimplePlugin
This plugin provides instruction decoding capabilities to others plugins. This plugin provides instruction decoding capabilities to others plugins.
For instance, for a given instruction, the pipeline hazard plugin needs to know if it uses the register file source 1/2 in order stall the pipeline until the hazard is gone. For instance, for a given instruction, the pipeline hazard plugin needs to know if it uses the register file source 1/2 in order stall the pipeline until the hazard is gone.
To provide this kind of information, each plugin which implements an instruction documents this kind of information to the DecoderSimplePlugin plugin. To provide this kind of information, each plugin which implements an instruction documents this kind of information to the DecoderSimplePlugin plugin.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| catchIllegalInstruction | Boolean | If set to true, instruction which have no decoding specification will generate a trap exception | | catchIllegalInstruction | Boolean | If set to true, instruction which have no decoding specification will generate a trap exception |
Here is a usage example : Here is a usage example :
```scala ```scala
//Specify the instruction decoding which should be applied when the instruction match the 'key' pattern //Specify the instruction decoding which should be applied when the instruction match the 'key' pattern
@ -767,7 +770,7 @@ This plugin operates in the Decode stage.
This plugin implements the register file. This plugin implements the register file.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| regFileReadyKind | RegFileReadKind | Can bet set to ASYNC or SYNC. Specifies the kind of memory read used to implement the register file. ASYNC means zero cycle latency memory read, while SYNC means one cycle latency memory read which can be mapped into standard FPGA memory blocks | | regFileReadyKind | RegFileReadKind | Can bet set to ASYNC or SYNC. Specifies the kind of memory read used to implement the register file. ASYNC means zero cycle latency memory read, while SYNC means one cycle latency memory read which can be mapped into standard FPGA memory blocks |
| zeroBoot | Boolean | Load all registers with zeroes at the beginning of simulations to keep everything deterministic in logs/traces| | zeroBoot | Boolean | Load all registers with zeroes at the beginning of simulations to keep everything deterministic in logs/traces|
@ -775,13 +778,13 @@ This register file use a `don't care` read-during-write policy, so the bypassing
#### HazardSimplePlugin #### HazardSimplePlugin
This plugin checks the pipeline instruction dependencies and, if necessary or possible, will stop the instruction in the decoding stage or bypass the instruction results This plugin checks the pipeline instruction dependencies and, if necessary or possible, will stop the instruction in the decoding stage or bypass the instruction results
from the later stages to the decode stage. from the later stages to the decode stage.
Since the register file is implemented with a `don't care` read-during-write policy, this plugin also manages these kind of hazards. Since the register file is implemented with a `don't care` read-during-write policy, this plugin also manages these kind of hazards.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| bypassExecute | Boolean | Enable the bypassing of instruction results coming from the Execute stage | | bypassExecute | Boolean | Enable the bypassing of instruction results coming from the Execute stage |
| bypassMemory | Boolean | Enable the bypassing of instruction results coming from the Memory stage | | bypassMemory | Boolean | Enable the bypassing of instruction results coming from the Memory stage |
| bypassWriteBack | Boolean | Enable the bypassing of instruction results coming from the WriteBack stage | | bypassWriteBack | Boolean | Enable the bypassing of instruction results coming from the WriteBack stage |
@ -792,7 +795,7 @@ Since the register file is implemented with a `don't care` read-during-write pol
This plugin muxes different input values to produce SRC1/SRC2/SRC_ADD/SRC_SUB/SRC_LESS values which are common values used by many plugins in the execute stage (ALU/Branch/Load/Store). This plugin muxes different input values to produce SRC1/SRC2/SRC_ADD/SRC_SUB/SRC_LESS values which are common values used by many plugins in the execute stage (ALU/Branch/Load/Store).
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| separatedAddSub | RegFileReadKind | By default SRC_ADD/SRC_SUB are generated from a single controllable adder/substractor, but if this is set to true, it use separate adder/substractors | | separatedAddSub | RegFileReadKind | By default SRC_ADD/SRC_SUB are generated from a single controllable adder/substractor, but if this is set to true, it use separate adder/substractors |
| executeInsertion | Boolean | By default SRC1/SRC2 are generated in the Decode stage, but if this parameter is true, it is done in the Execute stage (It will relax the bypassing network) | | executeInsertion | Boolean | By default SRC1/SRC2 are generated in the Decode stage, but if this parameter is true, it is done in the Execute stage (It will relax the bypassing network) |
@ -815,16 +818,16 @@ The result is injected into the pipeline directly at the end of the execute stag
Implements SLL/SRL/SRA instructions by using a full barrel shifter, so it execute all shifts in a single cycle. Implements SLL/SRL/SRA instructions by using a full barrel shifter, so it execute all shifts in a single cycle.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| earlyInjection | Boolean | By default the result of the shift is injected into the pipeline in the Memory stage to relax timings, but if this option is true it will be done in the Execute stage | | earlyInjection | Boolean | By default the result of the shift is injected into the pipeline in the Memory stage to relax timings, but if this option is true it will be done in the Execute stage |
#### BranchPlugin #### BranchPlugin
This plugin implements all branch/jump instructions (JAL/JALR/BEQ/BNE/BLT/BGE/BLTU/BGEU) with some optional branch prediction. Each of these branch predictions could have been implemented This plugin implements all branch/jump instructions (JAL/JALR/BEQ/BNE/BLT/BGE/BLTU/BGEU) with some optional branch prediction. Each of these branch predictions could have been implemented
as separate plugin. as separate plugin.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| earlyBranch | Boolean | By default the branch is done in the Memory stage to relax timings, but if this option is set it's done in the Execute stage| | earlyBranch | Boolean | By default the branch is done in the Memory stage to relax timings, but if this option is set it's done in the Execute stage|
| catchAddressMisaligned | Boolean | If a jump/branch is done in an unaligned PC address, it will fire a trap exception | | catchAddressMisaligned | Boolean | If a jump/branch is done in an unaligned PC address, it will fire a trap exception |
| prediction | BranchPrediction | Can be set to NONE/STATIC/DYNAMIC/DYNAMIC_TARGET to specify the branch predictor implementation, see below for more descriptions | | prediction | BranchPrediction | Can be set to NONE/STATIC/DYNAMIC/DYNAMIC_TARGET to specify the branch predictor implementation, see below for more descriptions |
@ -838,7 +841,7 @@ No prediction: each PC change due to a jump/branch will produce a penalty.
##### Prediction STATIC ##### Prediction STATIC
In the decode stage, a conditional branch pointing backwards or a JAL is branched speculatively. If the speculation is right, the branch penalty is reduced to a single cycle, In the decode stage, a conditional branch pointing backwards or a JAL is branched speculatively. If the speculation is right, the branch penalty is reduced to a single cycle,
otherwise the standard penalty is applied. otherwise the standard penalty is applied.
##### Prediction DYNAMIC ##### Prediction DYNAMIC
@ -847,8 +850,8 @@ Same as the STATIC prediction, except that to do the prediction, it use a direct
##### Prediction DYNAMIC_TARGET ##### Prediction DYNAMIC_TARGET
This predictor uses a direct mapped branch target buffer (BTB) in the Fetch stage which store the PC of the instruction, the target PC of the instruction and a 2 bit history to remember This predictor uses a direct mapped branch target buffer (BTB) in the Fetch stage which store the PC of the instruction, the target PC of the instruction and a 2 bit history to remember
if the branch is more likely to be taken or not. This is the most efficient branch predictor actualy implemented on VexRiscv as when the branch prediction is right, it produce no branch penalty. if the branch is more likely to be taken or not. This is the most efficient branch predictor actualy implemented on VexRiscv as when the branch prediction is right, it produce no branch penalty.
The down side is that this predictor has a long combinatorial path coming from the prediction cache read port to the programm counter by passing through the jump interface. The down side is that this predictor has a long combinatorial path coming from the prediction cache read port to the programm counter by passing through the jump interface.
#### DBusSimplePlugin #### DBusSimplePlugin
@ -856,7 +859,7 @@ The down side is that this predictor has a long combinatorial path coming from t
This plugin implements the load and store instructions (LB/LH/LW/LBU/LHU/LWU/SB/SH/SW) via a simple and neutral memory bus going out of the CPU. This plugin implements the load and store instructions (LB/LH/LW/LBU/LHU/LWU/SB/SH/SW) via a simple and neutral memory bus going out of the CPU.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| catchAddressMisaligned | Boolean | If a memory access is done to an unaligned memory address, it will fire a trap exception | | catchAddressMisaligned | Boolean | If a memory access is done to an unaligned memory address, it will fire a trap exception |
| catchAccessFault | Boolean | If a memory read returns an error, it will fire a trap exception | | catchAccessFault | Boolean | If a memory read returns an error, it will fire a trap exception |
| earlyInjection | Boolean | By default, the memory read values are injected into the pipeline in the WriteBack stage to relax the timings. If this parameter is true, it's done in the Memory stage | | earlyInjection | Boolean | By default, the memory read values are injected into the pipeline in the WriteBack stage to relax the timings. If this parameter is true, it's done in the Memory stage |
@ -903,15 +906,15 @@ Single way cache implementation with a victim buffer. (Documentation is WIP)
#### MulPlugin #### MulPlugin
Implements the multiplication instruction from the RISC-V M extension. Its implementation was done in a FPGA friendly way by using 4 17*17 bit multiplications. Implements the multiplication instruction from the RISC-V M extension. Its implementation was done in a FPGA friendly way by using 4 17*17 bit multiplications.
The processing is fully pipelined between the Execute/Memory/Writeback stage. The results of the instructions are always inserted in the WriteBack stage. The processing is fully pipelined between the Execute/Memory/Writeback stage. The results of the instructions are always inserted in the WriteBack stage.
#### DivPlugin #### DivPlugin
Implements the division/modulo instruction from the RISC-V M extension. It is done in a simple iterative way which always takes 34 cycles. The result is inserted into the Implements the division/modulo instruction from the RISC-V M extension. It is done in a simple iterative way which always takes 34 cycles. The result is inserted into the
Memory stage. Memory stage.
This plugin is now based on the MulDivIterativePlugin one. This plugin is now based on the MulDivIterativePlugin one.
#### MulDivIterativePlugin #### MulDivIterativePlugin
@ -920,7 +923,7 @@ This plugin implements the multiplication, division and modulo of the RISC-V M e
This plugin is able to unroll the iterative calculation process to reduce the number of cycles used to execute mul/div instructions. This plugin is able to unroll the iterative calculation process to reduce the number of cycles used to execute mul/div instructions.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| genMul | Boolean | Enables multiplication support. Can be set to false if you want to use the MulPlugin instead | | genMul | Boolean | Enables multiplication support. Can be set to false if you want to use the MulPlugin instead |
| genDiv | Boolean | Enables division support | | genDiv | Boolean | Enables division support |
| mulUnrollFactor | Int | Number of combinatorial stages used to speed up the multiplication, should be > 0 | | mulUnrollFactor | Int | Number of combinatorial stages used to speed up the multiplication, should be > 0 |
@ -933,13 +936,13 @@ Both mul/div are processed into the memory stage (late result).
#### CsrPlugin #### CsrPlugin
Implements most of the Machine mode and a few of the User mode registers as specified in the RISC-V priviledged spec. Implements most of the Machine mode and a few of the User mode registers as specified in the RISC-V priviledged spec.
The access mode of most of the CSR is parameterizable (NONE/READ_ONLY/WRITE_ONLY/READ_WRITE) to reduce the area usage of unneeded features. The access mode of most of the CSR is parameterizable (NONE/READ_ONLY/WRITE_ONLY/READ_WRITE) to reduce the area usage of unneeded features.
(CsrAccess can be NONE/READ_ONLY/WRITE_ONLY/READ_WRITE) (CsrAccess can be NONE/READ_ONLY/WRITE_ONLY/READ_WRITE)
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| catchIllegalAccess | Boolean | | | catchIllegalAccess | Boolean | |
| mvendorid | BigInt | | | mvendorid | BigInt | |
| marchid | BigInt | | | marchid | BigInt | |
@ -961,7 +964,7 @@ The access mode of most of the CSR is parameterizable (NONE/READ_ONLY/WRITE_ONLY
If an interrupt occurs, before jumping to mtvec, the plugin will stop the Prefetch stage and wait for all the instructions in the later pipeline stages to complete their execution. If an interrupt occurs, before jumping to mtvec, the plugin will stop the Prefetch stage and wait for all the instructions in the later pipeline stages to complete their execution.
If an exception occur, the plugin will kill the corresponding instruction, flush all previous instructions, and wait until the previously killed instructions reach the WriteBack If an exception occur, the plugin will kill the corresponding instruction, flush all previous instructions, and wait until the previously killed instructions reach the WriteBack
stage before jumping to mtvec. stage before jumping to mtvec.
#### StaticMemoryTranslatorPlugin #### StaticMemoryTranslatorPlugin
@ -970,21 +973,21 @@ Static memory translator plugin which allows one to specify which range of the m
#### MemoryTranslatorPlugin #### MemoryTranslatorPlugin
Simple software refilled MMU implementation. Allows others plugins such as DBusCachedPlugin/IBusCachedPlugin to instanciate memory address translation ports. Each port has a small dedicated Simple software refilled MMU implementation. Allows others plugins such as DBusCachedPlugin/IBusCachedPlugin to instanciate memory address translation ports. Each port has a small dedicated
fully associative TLB cache which is refilled from a larger software filled TLB cache via a query which looks up one entry per cycle. fully associative TLB cache which is refilled from a larger software filled TLB cache via a query which looks up one entry per cycle.
#### DebugPlugin #### DebugPlugin
This plugin implements enough CPU debug features to allow comfortable GDB/Eclipse debugging. To access those debug features, it provides a simple memory bus interface. This plugin implements enough CPU debug features to allow comfortable GDB/Eclipse debugging. To access those debug features, it provides a simple memory bus interface.
The JTAG interface is provided by another bridge, which makes it possible to efficiently connect multiple CPUs to the same JTAG. The JTAG interface is provided by another bridge, which makes it possible to efficiently connect multiple CPUs to the same JTAG.
| Parameters | type | description | | Parameters | type | description |
| ------ | ----------- | ------ | | ------ | ----------- | ------ |
| debugClockDomain | ClockDomain | As the debug unit is able to reset the CPU itself, it should use another clock domain to avoid killing itself (only the reset wire should differ) | | debugClockDomain | ClockDomain | As the debug unit is able to reset the CPU itself, it should use another clock domain to avoid killing itself (only the reset wire should differ) |
The internals of the debug plugin are done in a manner which reduces the area usage and the FMax impact of this plugin. The internals of the debug plugin are done in a manner which reduces the area usage and the FMax impact of this plugin.
Here is the simple bus to access it, the rsp come one cycle after the request : Here is the simple bus to access it, the rsp come one cycle after the request :
```scala ```scala
case class DebugExtensionCmd() extends Bundle{ case class DebugExtensionCmd() extends Bundle{
@ -998,17 +1001,17 @@ case class DebugExtensionRsp() extends Bundle{
case class DebugExtensionBus() extends Bundle with IMasterSlave{ case class DebugExtensionBus() extends Bundle with IMasterSlave{
val cmd = Stream(DebugExtensionCmd()) val cmd = Stream(DebugExtensionCmd())
val rsp = DebugExtensionRsp() val rsp = DebugExtensionRsp()
override def asMaster(): Unit = { override def asMaster(): Unit = {
master(cmd) master(cmd)
in(rsp) in(rsp)
} }
} }
``` ```
Here is the register mapping : Here is the register mapping :
``` ```
Read address 0x00 -> Read address 0x00 ->
@ -1023,7 +1026,7 @@ Write address 0x00 ->
bit 17 : set haltIt bit 17 : set haltIt
bit 24 : clear resetIt bit 24 : clear resetIt
bit 25 : clear haltIt and haltedByBreak bit 25 : clear haltIt and haltedByBreak
Read Address 0x04 -> Read Address 0x04 ->
bits (31 downto 0) : Last value written into the register file bits (31 downto 0) : Last value written into the register file
Write Address 0x04 -> Write Address 0x04 ->
@ -1035,7 +1038,7 @@ https://github.com/SpinalHDL/openocd_riscv
#### YamlPlugin #### YamlPlugin
This plugin offers a service to others plugins to generate a usefull Yaml file about the CPU configuration. It contains, for instance, the sequence of instruction required This plugin offers a service to others plugins to generate a usefull Yaml file about the CPU configuration. It contains, for instance, the sequence of instruction required
to flush the data cache (information used by openocd). to flush the data cache (information used by openocd).