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(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(&i8253_clockevent)) 34 return 0; 35 36 return clocksource_i8253_init(); 37 } 38 arch_initcall(init_pit_clocksource); 39