From e03b2ed579e84967648796897bd8aaf4256319e9 Mon Sep 17 00:00:00 2001
From: Freya Murphy <freya@freyacat.org>
Date: Sun, 20 Apr 2025 19:56:27 -0400
Subject: PIT (timer)

---
 kernel/cpu/idt.c                   | 10 ++--------
 kernel/drivers.c                   |  2 ++
 kernel/drivers/pit.c               | 23 +++++++++++++++++++++++
 kernel/include/comus/drivers/pit.h | 21 +++++++++++++++++++++
 4 files changed, 48 insertions(+), 8 deletions(-)
 create mode 100644 kernel/drivers/pit.c
 create mode 100644 kernel/include/comus/drivers/pit.h

(limited to 'kernel')

diff --git a/kernel/cpu/idt.c b/kernel/cpu/idt.c
index 8b4465f..42cf651 100644
--- a/kernel/cpu/idt.c
+++ b/kernel/cpu/idt.c
@@ -2,6 +2,7 @@
 #include <comus/memory.h>
 #include <comus/asm.h>
 #include <comus/cpu.h>
+#include <comus/drivers/pit.h>
 
 #include "idt.h"
 #include "pic.h"
@@ -153,14 +154,7 @@ int counter = 0;
 
 void idt_pic_timer(void)
 {
-	// print a message once we know the timer works
-	// but avoid spamming the logs
-	if (counter == 3) {
-		//kputs("pic timer!\n");
-	}
-	if (counter <= 3) {
-		counter++;
-	}
+	ticks++;
 }
 
 void idt_pic_keyboard(void)
diff --git a/kernel/drivers.c b/kernel/drivers.c
index 04145db..15de4df 100644
--- a/kernel/drivers.c
+++ b/kernel/drivers.c
@@ -3,10 +3,12 @@
 #include <comus/drivers/uart.h>
 #include <comus/drivers/pci.h>
 #include <comus/drivers/gpu.h>
+#include <comus/drivers/pit.h>
 #include <comus/mboot.h>
 
 void drivers_init(void)
 {
+	pit_set_divider(100); // 1ms
 	uart_init();
 	pci_init();
 	acpi_init(mboot_get_rsdp());
diff --git a/kernel/drivers/pit.c b/kernel/drivers/pit.c
new file mode 100644
index 0000000..cb3c091
--- /dev/null
+++ b/kernel/drivers/pit.c
@@ -0,0 +1,23 @@
+#include <comus/asm.h>
+#include <comus/drivers/pit.h>
+
+#define CHAN_0 0x40
+#define CHAN_1 0x41
+#define CHAN_2 0x42
+#define CMD 0x43
+
+uint64_t ticks = 0;
+
+uint16_t pit_read_divider(void) {
+	uint16_t count = 0;
+	cli();
+	outb(CMD, 0); // clear bits
+	count = inb(CHAN_0); // low byte
+	count |= inb(CHAN_0)<<8; // highbyte
+	return count;
+}
+
+void pit_set_divider(uint16_t count) {
+	outb(CHAN_0, count & 0xFF); // low byte
+	outb(CHAN_0, (count & 0xFF00) >> 8); // high byte
+}
diff --git a/kernel/include/comus/drivers/pit.h b/kernel/include/comus/drivers/pit.h
new file mode 100644
index 0000000..a7a111d
--- /dev/null
+++ b/kernel/include/comus/drivers/pit.h
@@ -0,0 +1,21 @@
+/**
+ * @file pit.h
+ *
+ * @author Freya Murphy <freya@freyacat.org>
+ *
+ * Programmable Interrupt Timer
+ */
+
+#ifndef PIT_H_
+#define PIT_H_
+
+#include <stdint.h>
+
+// how many time the pit has ticked
+// not accurate time, good for spinning though
+extern uint64_t ticks;
+
+uint16_t pit_read_divider(void);
+void pit_set_divider(uint16_t count);
+
+#endif
-- 
cgit v1.2.3-freya