Added cpu timer

Well, it doesn't work *at all*. When I include these files with the
Makefile everything crashes. I *think* this is due to the fact that the
bootloader only handles direct ext2 pointer and the kernel is too big to
fit into them. Therefore the kernel taps into the void as it tries to
read some data an crashes.

It could be something completely different though - let's see!
(this will take some time ig)

2 files changed, 49 insertions, 0 deletions

diff --git a/src/drivers/timer.c b/src/drivers/timer.c
new file mode 100644
index 0000000..922b385
--- /dev/null
+++ b/src/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);
+}
diff --git a/src/inc/timer.h b/src/inc/timer.h
new file mode 100644
index 0000000..4b2bb8c
--- /dev/null
+++ b/src/inc/timer.h
@@ -0,0 +1,10 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+
+#ifndef TIMER_H
+#define TIMER_H
+
+#include <def.h>
+
+void timer_install();
+
+#endif