1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * i8253.c  8253/PIT functions
4  *
5  */
6 #include <linux/clockchips.h>
7 #include <linux/i8253.h>
8 #include <linux/export.h>
9 #include <linux/smp.h>
10 #include <linux/irq.h>
11 
12 #include <asm/time.h>
13 
timer_interrupt(int irq,void * dev_id)14 static irqreturn_t timer_interrupt(int irq, void *dev_id)
15 {
16 	i8253_clockevent.event_handler(&i8253_clockevent);
17 
18 	return IRQ_HANDLED;
19 }
20 
21 static struct irqaction irq0  = {
22 	.handler = timer_interrupt,
23 	.flags = IRQF_NOBALANCING | IRQF_TIMER,
24 	.name = "timer"
25 };
26 
setup_pit_timer(void)27 void __init setup_pit_timer(void)
28 {
29 	clockevent_i8253_init(true);
30 	setup_irq(0, &irq0);
31 }
32 
init_pit_clocksource(void)33 static int __init init_pit_clocksource(void)
34 {
35 	if (num_possible_cpus() > 1 || /* PIT does not scale! */
36 	    !clockevent_state_periodic(&i8253_clockevent))
37 		return 0;
38 
39 	return clocksource_i8253_init();
40 }
41 arch_initcall(init_pit_clocksource);
42