Added functions to read registers and print information on failure. Also added a getTime function for a pretty boot display.

fpga/zsbl/fail.c

@@ -0,0 +1,19 @@
+#include "fail.h"
+#include "uart.h"
+#include "riscv.h"
+#include "time.h"
+
+void fail() {
+  // Get address that led to failure
+  register uint64_t addr;
+  asm volatile ("mv %0, ra" : "=r"(addr) : : "memory"); 
+
+  // Print message
+  print_time();
+  println_with_addr("Failed at: 0x", addr);
+  
+  // Loop forever
+  while(1) {
+
+  }
+}

fpga/zsbl/fail.h

@@ -0,0 +1,4 @@
+#pragma once
+#include <stdint.h>
+
+void fail();

fpga/zsbl/riscv.S

@@ -0,0 +1,29 @@
+.section .text
+.globl read_mcycle
+.type read_mcycle, @function
+read_mcycle:
+    csrr a0, mcycle
+    ret
+
+.section .text
+.globl get_ra
+.type get_ra, @function
+get_ra:
+    mv a0, ra
+    ret
+
+.section .text
+.globl set_status_fs
+.type set_status_fs, @function    
+set_status_fs:
+    lui t1, 0x6
+    csrs mstatus, t1
+    ret
+
+.section .text
+.globl clear_status_fs
+.type clear_status_fs, @function 
+clear_status_fs:
+    lui t1, 0x6
+    csrc mstatus, t1
+    ret

fpga/zsbl/riscv.h

@@ -0,0 +1,7 @@
+#pragma once
+#include <stdint.h>
+
+uint64_t read_mcycle();
+uint64_t get_ra();
+void set_status_fs();
+void clear_status_fs();

fpga/zsbl/time.c

@@ -0,0 +1,20 @@
+#include "time.h"
+#include "boot.h"
+#include "riscv.h"
+#include "uart.h"
+
+float getTime() {
+  set_status_fs();
+  float numCycles = (float)read_mcycle();
+  float ret = numCycles/SYSTEMCLOCK;
+  // clear_status_fs();
+  return ret;
+}
+
+void print_time() {
+  print_uart("[");
+  set_status_fs();
+  print_uart_float(getTime(),5);
+  clear_status_fs();
+  print_uart("] ");
+}

fpga/zsbl/time.h

@@ -0,0 +1,5 @@
+#pragma once
+#include <stdint.h>
+
+float getTime();
+void print_time();