From f3e85eedc434da973267f360abdbb79cb6f24100 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Thu, 1 Jul 2021 21:13:01 +0200
Subject: Timing is everything

---
 kernel/features/timer.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 kernel/features/timer.c

(limited to 'kernel/features/timer.c')

diff --git a/kernel/features/timer.c b/kernel/features/timer.c
new file mode 100644
index 0000000..674dd1a
--- /dev/null
+++ b/kernel/features/timer.c
@@ -0,0 +1,115 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+
+#include <assert.h>
+#include <def.h>
+#include <dev.h>
+#include <drivers/cpu.h>
+#include <drivers/int.h>
+#include <drivers/pit.h>
+#include <drivers/rtc.h>
+#include <mem.h>
+#include <proc.h>
+#include <timer.h>
+
+static u32 timer_ticks = 0;
+
+u32 timer_get(void)
+{
+	return timer_ticks;
+}
+
+static void timer_handler(void)
+{
+	int_disable();
+	if (timer_ticks >= U32_MAX)
+		timer_ticks = 0;
+	else
+		timer_ticks++;
+	proc_timer_check(timer_ticks);
+	int_enable();
+}
+
+CLEAR void timer_install_handler(void)
+{
+	static u8 check = 0;
+	assert(check++ == 0);
+	int_event_handler_add(0, timer_handler);
+}
+
+// "Delay" function with CPU sleep
+void timer_wait(u32 ticks)
+{
+	u32 eticks = timer_ticks + ticks;
+	while (timer_ticks < eticks)
+		__asm__ volatile("sti\nhlt\ncli");
+}
+
+static struct timer timer_struct(void)
+{
+	struct proc *proc = proc_current();
+	struct timer timer = {
+		.rtc = rtc_stamp(),
+		.ticks.user = proc->ticks.user,
+		.ticks.kernel = proc->ticks.kernel,
+		.time = timer_get(),
+	};
+	return timer;
+}
+
+static res timer_read(void *buf, u32 offset, u32 count)
+{
+	UNUSED(offset);
+
+	// TODO: Make sleeping more accurate
+	struct proc *proc = proc_current();
+	if (proc->timer.mode == TIMER_MODE_SLEEP) {
+		dev_block(DEV_TIMER, proc);
+		proc->timer.mode = TIMER_MODE_DEFAULT;
+	}
+
+	struct timer timer = timer_struct();
+	memcpy_user(buf, &timer, MIN(count, sizeof(timer)));
+
+	return MIN(count, sizeof(timer));
+}
+
+static res timer_control(u32 request, void *arg1, void *arg2, void *arg3)
+{
+	UNUSED(arg2);
+	UNUSED(arg3);
+
+	switch (request) {
+	case DEVCTL_TIMER_SLEEP: {
+		struct proc *proc = proc_current();
+		proc->timer.mode = TIMER_MODE_SLEEP;
+		proc->timer.data = timer_ticks + (u32)arg1;
+		return EOK;
+	}
+	default:
+		return -EINVAL;
+	}
+}
+
+static res timer_ready(void)
+{
+	struct proc *proc = proc_current();
+	if (proc->timer.mode == TIMER_MODE_SLEEP) {
+		if (timer_ticks >= proc->timer.data)
+			return EOK;
+		return -EAGAIN;
+	}
+	return EOK;
+}
+
+// Install timer handler into IRQ0
+CLEAR void timer_install(void)
+{
+	// hpet_install(10000); // TODO: Reimplement hpet
+	pit_install();
+
+	struct dev_dev *dev = zalloc(sizeof(*dev));
+	dev->read = timer_read;
+	dev->control = timer_control;
+	dev->ready = timer_ready;
+	dev_add(DEV_TIMER, dev);
+}
-- 
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