I also changed the

TOOLCHAIN_PREFIX

to

riscv32-unknown-elf-gcc

, currently the error I am seeing is:

(chip) rhyang@rhyang-ThinkPad-P1:~/chip/caravel_board/stanford/blink$ make flash
#/home/rhyang/chip/riscv-tools-install/bin/riscv32-unknown-elf-gcc -O0 -march=rv32i -Wl,-Bstatic,-T,../sections.lds,--strip-debug -ffreestanding -nostdlib -o blink.elf ../start.s ../print_io.c blink.c
/home/rhyang/chip/riscv-tools-install/bin/riscv32-unknown-elf-gcc -I../ -I../generated/ -O0 -mabi=ilp32 -march=rv32i -D__vexriscv__ -Wl,-Bstatic,-T,../sections.lds,--strip-debug -ffreestanding -nostdlib -o blink.elf ../crt0_vex.S ../isr.c ../stub.c blink.c
../crt0_vex.S: Assembler messages:
../crt0_vex.S:59: Error: unrecognized opcode `csrw mtvec,a0', extension `zicsr' required
../crt0_vex.S:87: Error: unrecognized opcode `csrw mie,a0', extension `zicsr' required
../irq_vex.h: Assembler messages:
../irq_vex.h:31: Error: unrecognized opcode `csrw 3008,a5', extension `zicsr' required
make: *** [Makefile:22: blink.elf] Error 1