Run Ara in Genesys2

Forked from ara, the goal of this project is to boot linux on ara by genesys2 fpga board. Basically, I add peripherals imitating corev-apu of cva6.

I have added the following peripherals (address mapping is the same with corev-apu):

• bootrom
• uart
• spi (with a sdcard slot)
• timer
• clint
• plic
• riscv-debugger
• ddr3

Currently, linux has been booted successfully and patched appropriately for vector support. But it seems to ara has no mmu support so U/S mode vector program can't run correctly.

Usage Command

To use this repo, first install fusesoc and vivado in host machine, then:

• Follow the command of ara project first.
• Patch submodules common_cells and cva6 by fpga/common_cells.patch and cva6-dts.patch respectively.
• Run fusesoc library add ara . in root directory of project.
• Run fusesoc run --build --target synth-genesys2 --build-root fpga-genesys2 ara in root direcory of project to launch vivado to synthesis ara

After running, you should find generated bitstream xilinx_ara_soc.bit in directory build/fpga-genesys2/synth-genesys2-vivado/ara_0.runs/impl_1.

ChangeList for Cva6

In fpga/cva6-dts.patch, I add following changes:

• Modify device tree to contain current peripheral information.
• Change AXI4 id width from 4 into 3 for ariane.
• VS bits can be written from sstatus register.

Todo List

• Upload cva6-sdk patch (now, I have changed sdcard partition and board device tree).
• Add mmu support for ara.
• Fix illegal instruction error: currently, reading and writing VCSR will raise illegal instruction.
• Understanding why riscv-debugger and timer are essential for whole soc
  • Deleting debugger and timer, instruction access exception will be raised when fetching first U mode instruction.
  • Deleting timer, no output from U mode program.