add tinyusb

tinyusb/hw/bsp/fomu/crt0-vexriscv.S

@@ -0,0 +1,83 @@
+.global main
+.global isr
+
+.section .text.start
+.global _start
+
+_start:
+  j crt_init
+
+.section .text
+.global  trap_entry
+trap_entry:
+  sw x1,  - 1*4(sp)
+  sw x5,  - 2*4(sp)
+  sw x6,  - 3*4(sp)
+  sw x7,  - 4*4(sp)
+  sw x10, - 5*4(sp)
+  sw x11, - 6*4(sp)
+  sw x12, - 7*4(sp)
+  sw x13, - 8*4(sp)
+  sw x14, - 9*4(sp)
+  sw x15, -10*4(sp)
+  sw x16, -11*4(sp)
+  sw x17, -12*4(sp)
+  sw x28, -13*4(sp)
+  sw x29, -14*4(sp)
+  sw x30, -15*4(sp)
+  sw x31, -16*4(sp)
+  addi sp,sp,-16*4
+  call isr
+  lw x1 , 15*4(sp)
+  lw x5,  14*4(sp)
+  lw x6,  13*4(sp)
+  lw x7,  12*4(sp)
+  lw x10, 11*4(sp)
+  lw x11, 10*4(sp)
+  lw x12,  9*4(sp)
+  lw x13,  8*4(sp)
+  lw x14,  7*4(sp)
+  lw x15,  6*4(sp)
+  lw x16,  5*4(sp)
+  lw x17,  4*4(sp)
+  lw x28,  3*4(sp)
+  lw x29,  2*4(sp)
+  lw x30,  1*4(sp)
+  lw x31,  0*4(sp)
+  addi sp,sp,16*4
+  mret
+
+.text
+crt_init:
+  la sp, _estack - 4
+  la a0, trap_entry
+  csrw mtvec, a0
+
+bss_init:
+  la a0, _sbss
+  la a1, _ebss + 4
+bss_loop:
+  beq a0,a1,bss_done
+  sw zero,0(a0)
+  add a0,a0,4
+  j bss_loop
+bss_done:
+
+  /* Load DATA */
+  la t0, _etext
+  la t1, _srelocate
+  la t2, _erelocate + 4
+3:
+  lw t3, 0(t0)
+  sw t3, 0(t1)
+  /* _edata is aligned to 4 bytes. Use word-xfers. */
+  addi t0, t0, 4
+  addi t1, t1, 4
+  bltu t1, t2, 3b
+
+  li a0, 0x880  //880 enable timer + external interrupt sources (until mstatus.MIE is set, they will never trigger an interrupt)
+  csrw mie,a0
+
+  call main
+infinite_loop:
+  j infinite_loop