--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/timer.c	Sun Jan 06 19:27:03 2019 +0900
@@ -0,0 +1,81 @@
+/*****************************************************************
+*       timer.c
+*       by Zhiyi Huang, hzy@cs.otago.ac.nz
+*       University of Otago
+*
+********************************************************************/
+
+// The System Timer peripheral
+
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "memlayout.h"
+#include "proc.h"
+#include "traps.h"
+#include "arm.h"
+#include "spinlock.h"
+
+#define TIMER_REGS_BASE		(MMIO_VA+0x003000)
+#define CONTROL_STATUS		0x0 // control/status
+#define COUNTER_LO		0x4 // the time-stamp lower 32 bits
+#define COUNTER_HI		0x8 // the time-stamp higher 32 bits
+#define COMPARE0		0xc  // compare 0
+#define COMPARE1                0x10 // compare 1
+#define COMPARE2                0x14 // compare 2
+#define COMPARE3                0x18 // compare 3
+
+#define TIMER_FREQ		10000  // interrupt 100 times/sec.
+
+void 
+enabletimer3irq(void)
+{
+        intctrlregs *ip;
+
+        ip = (intctrlregs *)INT_REGS_BASE;
+        ip->gpuenable[0] |= 1 << IRQ_TIMER3; // enable the system timer3 irq
+}
+
+
+void 
+timer3init(void)
+{
+uint v;
+
+	enabletimer3irq();
+
+	v = inw(TIMER_REGS_BASE+COUNTER_LO);
+	v += TIMER_FREQ;
+
+	outw(TIMER_REGS_BASE+COMPARE3, v);
+	ticks = 0;
+}
+
+void 
+timer3intr(void)
+{
+uint v;
+//cprintf("timer3 interrupt: %x\n", inw(TIMER_REGS_BASE+CONTROL_STATUS));
+	outw(TIMER_REGS_BASE+CONTROL_STATUS, (1 << IRQ_TIMER3)); // clear timer3 irq
+
+	ticks++;
+	wakeup(&ticks);
+
+	// reset the value of compare3
+	v=inw(TIMER_REGS_BASE+COUNTER_LO);
+	v += TIMER_FREQ;
+	outw(TIMER_REGS_BASE+COMPARE3, v);
+}
+
+void
+delay(uint m)
+{
+	unsigned long long t;
+
+	if(m == 0) return;
+
+	t = getsystemtime() + m;
+	while(t != getsystemtime());
+
+	return;
+}