1/*
2 * ledtrig-cpu.c - LED trigger based on CPU activity
3 *
4 * This LED trigger will be registered for each possible CPU and named as
5 * cpu0, cpu1, cpu2, cpu3, etc.
6 *
7 * It can be bound to any LED just like other triggers using either a
8 * board file or via sysfs interface.
9 *
10 * An API named ledtrig_cpu is exported for any user, who want to add CPU
11 * activity indication in their code
12 *
13 * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
14 * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
15 *
16 * This program is free software; you can redistribute it and/or modify
17 * it under the terms of the GNU General Public License version 2 as
18 * published by the Free Software Foundation.
19 *
20 */
21
22#include <linux/module.h>
23#include <linux/kernel.h>
24#include <linux/init.h>
25#include <linux/slab.h>
26#include <linux/percpu.h>
27#include <linux/syscore_ops.h>
28#include <linux/rwsem.h>
29#include <linux/cpu.h>
30#include "../leds.h"
31
32#define MAX_NAME_LEN	8
33
34struct led_trigger_cpu {
35	char name[MAX_NAME_LEN];
36	struct led_trigger *_trig;
37};
38
39static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
40
41/**
42 * ledtrig_cpu - emit a CPU event as a trigger
43 * @evt: CPU event to be emitted
44 *
45 * Emit a CPU event on a CPU core, which will trigger a
46 * binded LED to turn on or turn off.
47 */
48void ledtrig_cpu(enum cpu_led_event ledevt)
49{
50	struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
51
52	/* Locate the correct CPU LED */
53	switch (ledevt) {
54	case CPU_LED_IDLE_END:
55	case CPU_LED_START:
56		/* Will turn the LED on, max brightness */
57		led_trigger_event(trig->_trig, LED_FULL);
58		break;
59
60	case CPU_LED_IDLE_START:
61	case CPU_LED_STOP:
62	case CPU_LED_HALTED:
63		/* Will turn the LED off */
64		led_trigger_event(trig->_trig, LED_OFF);
65		break;
66
67	default:
68		/* Will leave the LED as it is */
69		break;
70	}
71}
72EXPORT_SYMBOL(ledtrig_cpu);
73
74static int ledtrig_cpu_syscore_suspend(void)
75{
76	ledtrig_cpu(CPU_LED_STOP);
77	return 0;
78}
79
80static void ledtrig_cpu_syscore_resume(void)
81{
82	ledtrig_cpu(CPU_LED_START);
83}
84
85static void ledtrig_cpu_syscore_shutdown(void)
86{
87	ledtrig_cpu(CPU_LED_HALTED);
88}
89
90static struct syscore_ops ledtrig_cpu_syscore_ops = {
91	.shutdown	= ledtrig_cpu_syscore_shutdown,
92	.suspend	= ledtrig_cpu_syscore_suspend,
93	.resume		= ledtrig_cpu_syscore_resume,
94};
95
96static int ledtrig_cpu_notify(struct notifier_block *self,
97					   unsigned long action, void *hcpu)
98{
99	switch (action & ~CPU_TASKS_FROZEN) {
100	case CPU_STARTING:
101		ledtrig_cpu(CPU_LED_START);
102		break;
103	case CPU_DYING:
104		ledtrig_cpu(CPU_LED_STOP);
105		break;
106	}
107
108	return NOTIFY_OK;
109}
110
111
112static struct notifier_block ledtrig_cpu_nb = {
113	.notifier_call = ledtrig_cpu_notify,
114};
115
116static int __init ledtrig_cpu_init(void)
117{
118	int cpu;
119
120	/* Supports up to 9999 cpu cores */
121	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
122
123	/*
124	 * Registering CPU led trigger for each CPU core here
125	 * ignores CPU hotplug, but after this CPU hotplug works
126	 * fine with this trigger.
127	 */
128	for_each_possible_cpu(cpu) {
129		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
130
131		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
132
133		led_trigger_register_simple(trig->name, &trig->_trig);
134	}
135
136	register_syscore_ops(&ledtrig_cpu_syscore_ops);
137	register_cpu_notifier(&ledtrig_cpu_nb);
138
139	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
140
141	return 0;
142}
143module_init(ledtrig_cpu_init);
144
145static void __exit ledtrig_cpu_exit(void)
146{
147	int cpu;
148
149	unregister_cpu_notifier(&ledtrig_cpu_nb);
150
151	for_each_possible_cpu(cpu) {
152		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
153
154		led_trigger_unregister_simple(trig->_trig);
155		trig->_trig = NULL;
156		memset(trig->name, 0, MAX_NAME_LEN);
157	}
158
159	unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
160}
161module_exit(ledtrig_cpu_exit);
162
163MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
164MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
165MODULE_DESCRIPTION("CPU LED trigger");
166MODULE_LICENSE("GPL");
167