1 /*
2  *  linux/drivers/clocksource/dummy_timer.c
3  *
4  *  Copyright (C) 2013 ARM Ltd.
5  *  All Rights Reserved
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  */
11 #include <linux/clockchips.h>
12 #include <linux/cpu.h>
13 #include <linux/init.h>
14 #include <linux/percpu.h>
15 #include <linux/cpumask.h>
16 
17 static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);
18 
19 static void dummy_timer_setup(void)
20 {
21 	int cpu = smp_processor_id();
22 	struct clock_event_device *evt = raw_cpu_ptr(&dummy_timer_evt);
23 
24 	evt->name	= "dummy_timer";
25 	evt->features	= CLOCK_EVT_FEAT_PERIODIC |
26 			  CLOCK_EVT_FEAT_ONESHOT |
27 			  CLOCK_EVT_FEAT_DUMMY;
28 	evt->rating	= 100;
29 	evt->cpumask	= cpumask_of(cpu);
30 
31 	clockevents_register_device(evt);
32 }
33 
34 static int dummy_timer_cpu_notify(struct notifier_block *self,
35 				      unsigned long action, void *hcpu)
36 {
37 	if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
38 		dummy_timer_setup();
39 
40 	return NOTIFY_OK;
41 }
42 
43 static struct notifier_block dummy_timer_cpu_nb = {
44 	.notifier_call = dummy_timer_cpu_notify,
45 };
46 
47 static int __init dummy_timer_register(void)
48 {
49 	int err = 0;
50 
51 	cpu_notifier_register_begin();
52 	err = __register_cpu_notifier(&dummy_timer_cpu_nb);
53 	if (err)
54 		goto out;
55 
56 	/* We won't get a call on the boot CPU, so register immediately */
57 	if (num_possible_cpus() > 1)
58 		dummy_timer_setup();
59 
60 out:
61 	cpu_notifier_register_done();
62 	return err;
63 }
64 early_initcall(dummy_timer_register);
65