Implemented PIT

kernel/src/timer.c

@@ -0,0 +1,46 @@
+#include <kernel.h>
+#include <system.h>
+#include <isr.h>
+#include <tty.h>
+
+#include <timer.h>
+
+size_t timer_ticks = 0;
+
+int timer_init(void) {
+	// TODO: Check what timer we can use and select the best one
+	return pit_init();
+}
+
+void timer_wait(size_t t) {
+	size_t req = timer_ticks + t;
+	while (req != timer_ticks);
+}
+
+int pit_init(void) {
+	isr_register(0, pit_handler);
+	pit_phase(0, 2, 1000);
+	return 0;
+}
+
+void pit_phase(uint8_t ch, uint8_t mode, uint32_t hz) {
+	if (ch > 2 || mode > 7) return;
+	
+	__asm__ volatile ("cli");
+
+	outb(PIT_CMD, ((ch << 6) | (3 << 4) | (mode << 1)));
+
+	uint32_t div = PIT_DIV / hz;
+	debugf("[PIT] Setting PIT divisor to %d...\n", div);
+	outb(PIT_CH0 + ch, div & 0xFF);
+	outb(PIT_CH0 + ch, div >> 8);
+
+	__asm__ volatile ("sti");
+}
+
+void pit_handler(struct isr_int_frame* iframe) {
+	timer_ticks++;
+
+	if (timer_ticks % 1000 == 0) tty_puts(".");
+}
+