/* 
 * Copyright 2010 Stefan Lankes, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file is part of MetalSVM.
 */

#include <metalsvm/stdio.h>
#include <metalsvm/string.h>
#include <metalsvm/tasks.h>
#include <metalsvm/time.h>
#include <metalsvm/processor.h>
#include <metalsvm/errno.h>
#include <metalsvm/spinlock.h>
#include <asm/irq.h>
#include <asm/irqflags.h>
#include <asm/gdt.h>
#include <asm/tss.h>
#include <asm/vga.h>

typedef struct {
	uint8_t active;
	uint64_t timeout;
} timer_t;

static timer_t timers[MAX_TASKS] = {[0 ... MAX_TASKS-1] = {0, 0}};
static spinlock_irqsave_t timers_lock = SPINLOCK_IRQSAVE_INIT;

/* 
 * This will keep track of how many ticks the system
 * has been running for 
 */
static volatile uint64_t timer_ticks = 0;

uint64_t get_clock_tick(void)
{
	return timer_ticks;
}

int sys_times(struct tms* buffer, clock_t* clock)
{
	if (BUILTIN_EXPECT(!buffer, 0))
		return -EINVAL;
	if (BUILTIN_EXPECT(!clock, 0))
		return -EINVAL;

	memset(buffer, 0x00, sizeof(struct tms));
	*clock = buffer->tms_utime = (clock_t) ((timer_ticks - per_core(current_task)->start_tick) * CLOCKS_PER_SEC / TIMER_FREQ);

	return 0;
}

/* 
 * Handles the timer. In this case, it's very simple: We
 * increment the 'timer_ticks' variable every time the
 * timer fires. 
 */
static void timer_handler(struct state *s)
{
	uint32_t i;

	/* Increment our 'tick counter' */
#if MAX_CORES > 1
	if (smp_id() == 0)
#endif
	{
		timer_ticks++;

		spinlock_irqsave_lock(&timers_lock);
		for(i=1; i<MAX_TASKS; i++) {
			if (timers[i].active && (timer_ticks >= timers[i].timeout)) {
				timers[i].active = 0;
				wakeup_task(i);
			}
		}
		spinlock_irqsave_unlock(&timers_lock);
	}

	/* 
	 * Every TIMER_FREQ clocks (approximately 1 second), we will
	 * display a message on the screen 
	 */
	/*if (timer_ticks % TIMER_FREQ == 0) {
		vga_puts("One second has passed\n");
	}*/
}

/* 
 * This will continuously loop until the given time has
 * been reached 
 */
void timer_wait(unsigned int ticks)
{
	uint64_t eticks = timer_ticks + ticks;
	task_t* curr_task = per_core(current_task);

	// Task 0 is always an idle task
	// Perhaps, the status is not set correctly...
	if ((curr_task->status == TASK_IDLE) || (curr_task->id == 0))
	{
		while (timer_ticks < eticks) {
			check_workqueues();

			// recheck break condition
			if (timer_ticks >= eticks)
				break;

			HALT;
		}
	} else if (timer_ticks < eticks) {
		check_workqueues();

		spinlock_irqsave_lock(&timers_lock);
		if (timer_ticks < eticks) {
			timers[curr_task->id].active = 1;
			timers[curr_task->id].timeout = eticks;
			block_task(curr_task->id);
			spinlock_irqsave_unlock(&timers_lock);

			reschedule();
		} else spinlock_irqsave_unlock(&timers_lock);
	}
}

#define LATCH(f)	((CLOCK_TICK_RATE + f/2) / f)

/* 
 * Sets up the system clock by installing the timer handler
 * into IRQ0 
 */
int timer_init(void)
{
	uint64_t start;

	/* 
	 * Installs 'timer_handler' for the PIC and APIC timer,
	 * only one handler will be later used.
	 */
	irq_install_handler(32, timer_handler);
	irq_install_handler(123, timer_handler);

	/* 
	 * The Rock Creek processor doesn't posseess an tradional PIC.
	 * Therefore, we have not to configure the PIC timer.
	 */
#ifndef CONFIG_ROCKCREEK 
	outportb(0x43, 0x34);
	/* before we write to 0x40, we wait some time */
	start = rdtsc();
	while(rdtsc() - start < 1000000)
		;
	outportb(0x40, LATCH(TIMER_FREQ) & 0xFF);   /* low byte  */
	/* before we write to 0x40, we wait some time */
	start = rdtsc();
	while(rdtsc() - start < 1000000)
		;
	outportb(0x40, LATCH(TIMER_FREQ) >> 8);     /* high byte */
#endif

	return 0;
}