1 files changed, 39 insertions, 0 deletions
diff --git a/kernel/drivers/timer.c b/kernel/drivers/timer.c
new file mode 100644
index 0000000..a3b4137
--- /dev/null
+++ b/kernel/drivers/timer.c
@@ -0,0 +1,39 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+
+#include <cpu.h>
+#include <def.h>
+#include <interrupts.h>
+
+static u32 timer_ticks = 0;
+
+void timer_phase(int hz)
+{
+	int divisor = 3579545 / 3 / hz;
+	outb(0x43, 0x36); // 01 10 11 0b // CTR, RW, MODE, BCD
+	outb(0x40, divisor & 0xFF);
+	outb(0x40, divisor >> 8);
+}
+
+// Executed 1000 times per second
+void timer_handler()
+{
+	timer_ticks++;
+}
+
+// "Delay" function with CPU sleep
+void timer_wait(u32 ticks)
+{
+	u32 eticks;
+
+	eticks = timer_ticks + ticks;
+	while (timer_ticks < eticks) {
+		__asm__("sti//hlt//cli");
+	}
+}
+
+// Install timer handler into IRQ0
+void timer_install()
+{
+	timer_phase(1000);
+	irq_install_handler(0, timer_handler);
+}