Implemented PIT

TODO

@@ -10,10 +10,18 @@ TODO
 [x] Virtual MM
 [x] Paging
 [x] Serial monitor
-[ ] Timer interrupts
+[ ] Make dedicated asm functions like lidt(), sti(), ...
+[x] PIT
+[ ] RTC
+[ ] HPET
+[ ] System calls
+[ ] Userspace
+[ ] Processes
+[ ] Scheduler
 [ ] Task switching
-[ ] IPC
+[ ] Inter-process communication
 [ ] Graphics
+[ ] Multicore support
 [ ] Networking :)
 [ ] Finish all the TODOs
 [ ] Run DOOM

kernel/include/isr.h

@@ -16,7 +16,7 @@ struct isr_int_frame {
 typedef void (*isr_handler_ptr)(struct isr_int_frame* iframe);
 
 int isr_init(void);
-void isr_register_IRQ(uint8_t i, isr_handler_ptr handler);
+void isr_register(uint8_t i, isr_handler_ptr handler);
 int isr_handle_interrupt(struct isr_int_frame iframe);
 
 // Assembly definitions (isr.s)

kernel/include/system.h

@@ -3,6 +3,7 @@
 
 #include <kernel.h>
 
+// cpuid
 void cpuid(uint32_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx);
 
 // Ports

kernel/include/timer.h

@@ -0,0 +1,22 @@
+#ifndef _TIMER_H
+#define _TIMER_H
+
+#include <isr.h>
+
+#define PIT_DIV 1193180
+#define PIT_CH0	0x40
+#define PIT_CH1	0x41
+#define PIT_CH2	0x42
+#define PIT_CMD	0x43
+
+int  timer_init(void);
+void timer_wait(size_t ticks);
+
+int  pit_init(void);
+void pit_phase(uint8_t ch, uint8_t mode, uint32_t hz);
+void pit_handler(struct isr_int_frame* iframe);
+
+// TODO: rtc_init(void);
+// TODO: hpet_init(void);
+
+#endif

kernel/src/isr.c

@@ -75,28 +75,26 @@ int isr_init(void) {
 	return 0;
 }
 
-void isr_register_irq(uint8_t i, isr_handler_ptr handler) {
+void isr_register(uint8_t i, isr_handler_ptr handler) {
+	if (i > 16) return; // Security 
 	irq_handlers[i] = handler;
 }
 
 void isr_send_eoi(uint8_t irq) {
-	if (irq >= 8) {
-		outb(0xa0, 0x20);
-	}
+	if (irq >= 8) outb(0xA0, 0x20);
 	outb(0x20, 0x20);
 }
 
+// TODO: Write fault handlers and make this more robust 
 int isr_handle_interrupt(struct isr_int_frame iframe) {
 	if (iframe.interrupt < 32) { 
 		// ISRs 0-31 - Exceptions
-		panic(exceptions[iframe.error]);
+		panic(exceptions[iframe.interrupt]);
 	} else if (iframe.interrupt >= 32 && iframe.interrupt < 48) {
 		// ISRs 32-47 - Hardware interrupts
 		uint8_t irq = iframe.interrupt - 32;
-		if (irq_handlers[irq]) {
-			irq_handlers[irq](&iframe);
-			isr_send_eoi(irq);
-		}
+		if (irq_handlers[irq]) irq_handlers[irq](&iframe);
+		isr_send_eoi(irq);
 	} else if (iframe.interrupt == 128) { 
 		// ISR 128 - System call
 		return syscall_handler(&iframe);

kernel/src/kernel.c

@@ -2,6 +2,7 @@
 #include <kernel.h>
 #include <paging.h>
 #include <serial.h>
+#include <timer.h>
 #include <gdt.h>
 #include <isr.h>
 #include <pmm.h>
@@ -29,13 +30,17 @@ void kmain(void* ptr, uint32_t magic) {
 	if (tty_init() != 0) panic("Failed to initalize TTY driver.");
 	tty_puts("kern.\n\n");
 
-	// TODO: Timer
-	// TODO: Scheduler
+	// Timer
+	if (timer_init() != 0) panic("Failed to initialize timer.");
+
 	// TODO: Syscalls
+	// TODO: Scheduler
 	// TODO: Interprocess communication
 	// TODO: Tasking
 	// TODO: Load & run /sbin/init
 
+	while (1);
+
 	panic("kmain() reached end.");
 }
 

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(".");
+}
+