From d0eef864dad134c482f853df5ef70caf522d3e9e Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.org>
Date: Fri, 16 Feb 2024 12:43:03 -0600
Subject: arch: i386: add operations to control PIT timer

Add a set of functions that control the programmable interrupt timer.
This will be used as the primary means of preemption on this
architecture.

Signed-off-by: Danny Holman <dholman@gymli.org>
---
 arch/i386/include/kernel/timer.h |  9 +++++++++
 arch/i386/kernel/timer.c         | 29 +++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 arch/i386/include/kernel/timer.h
 create mode 100644 arch/i386/kernel/timer.c

diff --git a/arch/i386/include/kernel/timer.h b/arch/i386/include/kernel/timer.h
new file mode 100644
index 0000000..0d90369
--- /dev/null
+++ b/arch/i386/include/kernel/timer.h
@@ -0,0 +1,9 @@
+#ifndef I386_TIMER_H
+#define I386_TIMER_H
+
+#include <kernel/isr.h>
+
+void timer_handler(struct isr_frame *frame);
+void timer_init(void);
+
+#endif
diff --git a/arch/i386/kernel/timer.c b/arch/i386/kernel/timer.c
new file mode 100644
index 0000000..9e53fbd
--- /dev/null
+++ b/arch/i386/kernel/timer.c
@@ -0,0 +1,29 @@
+#include <kernel/timer.h>
+#include <kernel/asm.h>
+#include <kernel/pic.h>
+#include <kernel/sched.h>
+
+static uint32_t num_ticks = 0;
+
+void timer_handler(struct isr_frame *frame) {
+        num_ticks++;
+        if (num_ticks == 3) {
+                num_ticks = 0;
+                //schedule_next();
+        }
+}
+
+void timer_init(void) {
+        asm __volatile__("cli");
+        int divisor = 1193182 / 100;
+        outb(0x43, 0x34);
+        outb(0x40, divisor && 0xFF);
+        outb(0x40, divisor && 0xFF00 >> 8);
+        asm __volatile__("sti");
+
+        //uint8_t read = 0;
+        //outb(0x43, 0xE2);
+        //read = inb(0x40);
+
+        register_irq_handler(0, timer_handler);
+}
-- 
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