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_set_mode(enum clock_event_mode mode,
20 			   struct clock_event_device *evt)
21 {
22 	/*
23 	 * Core clockevents code will call this when exchanging timer devices.
24 	 * We don't need to do anything here.
25 	 */
26 }
27 
28 static void dummy_timer_setup(void)
29 {
30 	int cpu = smp_processor_id();
31 	struct clock_event_device *evt = __this_cpu_ptr(&dummy_timer_evt);
32 
33 	evt->name	= "dummy_timer";
34 	evt->features	= CLOCK_EVT_FEAT_PERIODIC |
35 			  CLOCK_EVT_FEAT_ONESHOT |
36 			  CLOCK_EVT_FEAT_DUMMY;
37 	evt->rating	= 100;
38 	evt->set_mode	= dummy_timer_set_mode;
39 	evt->cpumask	= cpumask_of(cpu);
40 
41 	clockevents_register_device(evt);
42 }
43 
44 static int dummy_timer_cpu_notify(struct notifier_block *self,
45 				      unsigned long action, void *hcpu)
46 {
47 	if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
48 		dummy_timer_setup();
49 
50 	return NOTIFY_OK;
51 }
52 
53 static struct notifier_block dummy_timer_cpu_nb = {
54 	.notifier_call = dummy_timer_cpu_notify,
55 };
56 
57 static int __init dummy_timer_register(void)
58 {
59 	int err = 0;
60 
61 	cpu_notifier_register_begin();
62 	err = __register_cpu_notifier(&dummy_timer_cpu_nb);
63 	if (err)
64 		goto out;
65 
66 	/* We won't get a call on the boot CPU, so register immediately */
67 	if (num_possible_cpus() > 1)
68 		dummy_timer_setup();
69 
70 out:
71 	cpu_notifier_register_done();
72 	return err;
73 }
74 early_initcall(dummy_timer_register);
75