upgrade to latest rocket-chip

bootrom/bootrom.S

@@ -1,20 +1,23 @@
-.text
-.global _start
+#define DRAM_BASE 0x80000000
+
+.section .text.start, "ax", @progbits
+.globl _start
 _start:
+  csrr a0, mhartid
+  sll a0, a0, 2 // offset for hart msip
+  li a1, 0x2000000 // base address of clint
+  add a0, a0, a1
+  sw zero, 0(a0) // clear the interrupt
+  li a0, DRAM_BASE // program reset vector
+  csrw mepc, a0 // return from interrupt to start of user program
+  mret
+
+.section .text.hang, "ax", @progbits
+.globl _hang
+_hang:
   // This boot ROM doesn't know about any boot devices, so it just spins,
   // waiting for the serial interface to load the program and interrupt it
-  j setup_wfi_loop // reset vector
-  .word 0 // reserved
-  .word 0 // reserved
-  .word 0 // pointer to config string
-default_trap_vec:
-  j boot_trap // default trap vector
-  .word 0
-  .word 0
-  .word 0
-
-setup_wfi_loop:
-  la a0, default_trap_vec
+  la a0, _start
   csrw mtvec, a0
   li a0, 8 // MIE or MSIP bit
   csrw mie, a0 // set only MSIP in mie CSR
@@ -23,13 +26,3 @@ setup_wfi_loop:
 wfi_loop:
   wfi
   j wfi_loop
-
-boot_trap:
-  csrr a0, mhartid
-  sll a0, a0, 2 // offset for hart msip
-  li a1, 0x2000000 // base address of clint
-  add a0, a0, a1
-  sw zero, 0(a0) // clear the interrupt
-  li a0, 0x80000000 // program reset vector
-  csrw mepc, a0 // return from interrupt to start of user program
-  mret