| 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 | |
| 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 | void __init setup_pit_timer(void) |
| 22 | { |
| 23 | unsigned long flags = IRQF_NOBALANCING | IRQF_TIMER; |
| 24 | |
| 25 | clockevent_i8253_init(oneshot: true); |
| 26 | if (request_irq(0, timer_interrupt, flags, "timer", NULL)) |
| 27 | pr_err("Failed to request irq 0 (timer)\n"); |
| 28 | } |
| 29 | |
| 30 | static int __init init_pit_clocksource(void) |
| 31 | { |
| 32 | if (num_possible_cpus() > 1 || /* PIT does not scale! */ |
| 33 | !clockevent_state_periodic(dev: &i8253_clockevent)) |
| 34 | return 0; |
| 35 | |
| 36 | return clocksource_i8253_init(); |
| 37 | } |
| 38 | arch_initcall(init_pit_clocksource); |
| 39 |