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Add AES/FPU doc

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Dolu1990 2021-03-29 14:55:41 +02:00
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README.md
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@ -28,12 +28,13 @@
This repository hosts a RISC-V implementation written in SpinalHDL. Here are some specs : This repository hosts a RISC-V implementation written in SpinalHDL. Here are some specs :
- RV32I[M][C][A] instruction set (Atomic only inside a single core) - RV32I[M][A][F[D]][C] instruction set
- Pipelined from 2 to 5+ stages ([Fetch*X], Decode, Execute, [Memory], [WriteBack]) - Pipelined from 2 to 5+ stages ([Fetch*X], Decode, Execute, [Memory], [WriteBack])
- 1.44 DMIPS/Mhz --no-inline when nearly all features are enabled (1.57 DMIPS/Mhz when the divider lookup table is enabled) - 1.44 DMIPS/Mhz --no-inline when nearly all features are enabled (1.57 DMIPS/Mhz when the divider lookup table is enabled)
- Optimized for FPGA, does not use any vendor specific IP block / primitive - Optimized for FPGA, does not use any vendor specific IP block / primitive
- AXI4, Avalon, wishbone ready - AXI4, Avalon, wishbone ready
- Optional MUL/DIV extensions - Optional MUL/DIV extensions
- Optional F32/F64 FPU (require data cache for now)
- Optional instruction and data caches - Optional instruction and data caches
- Optional hardware refilled MMU - Optional hardware refilled MMU
- Optional debug extension allowing Eclipse debugging via a GDB >> openOCD >> JTAG connection - Optional debug extension allowing Eclipse debugging via a GDB >> openOCD >> JTAG connection
@ -688,7 +689,7 @@ Features :
Accuracy, roundings (RNE, RTZ, RDN, RUP, RMM) and compliance: Accuracy, roundings (RNE, RTZ, RDN, RUP, RMM) and compliance:
- Fully implemented excepted in the cases specified bellow - Fully implemented excepted in the cases specified bellow
- In FMA, the result of the multiplication is truncated before the addition (keep mantissa width bits) - In FMA, the result of the multiplication is rounded before the addition (keep mantissa width + 2 bits)
- A very special corner case of underflow flag do not follow IEEE 754 (rounding from subnormal to normal number) - A very special corner case of underflow flag do not follow IEEE 754 (rounding from subnormal to normal number)
- Very specific, but SGNJ instruction will not mutate the value from/to F32/F64 (no NaN-boxing mutation) - Very specific, but SGNJ instruction will not mutate the value from/to F32/F64 (no NaN-boxing mutation)
@ -1150,4 +1151,13 @@ Allow the integration of a internal or a external FPU into VexRiscv (See the FPU
| externalFpu | Boolean | When false the FPU is instanciated in Vex, else the plugin has a `port` interface to which you can connect an external FPU | | externalFpu | Boolean | When false the FPU is instanciated in Vex, else the plugin has a `port` interface to which you can connect an external FPU |
| p | FpuParameter | Parameter with which the connected FPU will be created | | p | FpuParameter | Parameter with which the connected FPU will be created |
#### AesPlugin
This plugin allow to accelerate AES encryption/decryption by using an internal ROM to solve SBOX and permutations, allowing in practice to execute one AES round in about 21 cycles.
For more documentation, check src/main/scala/vexriscv/plugin/AesPlugin.scala, a software C driver can be found here : <https://github.com/SpinalHDL/SaxonSoc/blob/dev-0.3/software/standalone/driver/aes_custom.h>
It was also ported on libressl via the following patch :
<https://github.com/SpinalHDL/buildroot-spinal-saxon/blob/main/patches/libressl/0000-vexriscv-aes.patch>
Speed up of 4 was observed in libressl running in linux. <https://github.com/SpinalHDL/SaxonSoc/pull/53#issuecomment-730133020>