timer.c

#include "bootpack.h"
// PIT 间隔型定时器8254
#define PIT_CTRL 0x0043
#define PIT_CNT0 0x0040
#define TIMER_FLAGS_FREE 0 // 闲置状态
#define TIMER_FLAGS_ALLOC 1 // 已配置状态
#define TIMER_FLAGS_USING 2 // 定时器使用中

void init_pit(void)
{
	int i;
	struct TIMER *t;
	io_out8(PIT_CTRL, 0x34);
	io_out8(PIT_CNT0, 0x9c); //0x2e9c = 11932, 中断产生的频率是100Hz，即每10ms中断一次
	io_out8(PIT_CNT0, 0x2e);
	timerctl.count = 0;
	timerctl.next = 0xffffffff;
	for (i = 0; i < MAX_TIMER; ++i)
	{
		timerctl.timers0[i].flags = TIMER_FLAGS_FREE;
	}
	t = timer_alloc();
	t->timeout = 0xffffffff;
	t->flags = TIMER_FLAGS_USING;
	t->next = 0;
	timerctl.t0 = t;
	return;
}

struct TIMER *timer_alloc(void)
{
	int i;
	for (i = 0; i < MAX_TIMER; ++i)
	{
		if (timerctl.timers0[i].flags == TIMER_FLAGS_FREE)
		{
			timerctl.timers0[i].flags = TIMER_FLAGS_ALLOC;
			return &timerctl.timers0[i];
		}
	}
	return 0;
}

void timer_free(struct TIMER *timer)
{
	timer->flags = TIMER_FLAGS_FREE;
	return;
}

void timer_init(struct TIMER *timer, struct FIFO32 *fifo, int data)
{
	timer->fifo = fifo;
	timer->data = data;
	return;
}

void timer_settime(struct TIMER *timer, unsigned int timeout)
{
	int e;
	struct TIMER *t, *s;
	timer->timeout = timeout + timerctl.count;
	timer->flags = TIMER_FLAGS_USING;
	e = io_load_eflags();
	io_cli();
	t = timerctl.t0;
	if (timer->timeout <= t->timeout)
	{
		timerctl.t0 = timer;
		timer->next = t;
		timerctl.next = timer->timeout;
		io_store_eflags(e);
		return;
	}
	for (;;)
	{
		s = t;
		t = t->next;
		if (t == 0) break;
		if (timer->timeout <= t->timeout)
		{
			s->next = timer;
			timer->next = t;
			io_store_eflags(e);
			return;
		}
	}
	io_store_eflags(e);
	return;
}

void inthandler20(int *esp)
{
	char ts = 0;
	struct TIMER *timer;
	io_out8(PIC0_OCW2, 0x60);
	timerctl.count++;
	if (timerctl.next > timerctl.count)
		return;
	timer = timerctl.t0;
	for (;;)
	{
		if (timer->timeout > timerctl.count)
			break;
		timer->flags = TIMER_FLAGS_ALLOC;
		if (timer != task_timer)
			fifo32_put(timer->fifo, timer->data);
		else
			ts = 1;
		timer = timer->next;
	}
	timerctl.t0 = timer;
	timerctl.next = timerctl.t0->timeout;
	if (ts != 0)
		task_switch();
	return;
}