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/kernel.h>
23 #include <linux/init.h>
24 #include <linux/slab.h>
25 #include <linux/percpu.h>
26 #include <linux/syscore_ops.h>
27 #include <linux/rwsem.h>
28 #include <linux/cpu.h>
29 #include "../leds.h"
30 
31 #define MAX_NAME_LEN	8
32 
33 struct led_trigger_cpu {
34 	char name[MAX_NAME_LEN];
35 	struct led_trigger *_trig;
36 };
37 
38 static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
39 
40 /**
41  * ledtrig_cpu - emit a CPU event as a trigger
42  * @evt: CPU event to be emitted
43  *
44  * Emit a CPU event on a CPU core, which will trigger a
45  * binded LED to turn on or turn off.
46  */
47 void ledtrig_cpu(enum cpu_led_event ledevt)
48 {
49 	struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
50 
51 	/* Locate the correct CPU LED */
52 	switch (ledevt) {
53 	case CPU_LED_IDLE_END:
54 	case CPU_LED_START:
55 		/* Will turn the LED on, max brightness */
56 		led_trigger_event(trig->_trig, LED_FULL);
57 		break;
58 
59 	case CPU_LED_IDLE_START:
60 	case CPU_LED_STOP:
61 	case CPU_LED_HALTED:
62 		/* Will turn the LED off */
63 		led_trigger_event(trig->_trig, LED_OFF);
64 		break;
65 
66 	default:
67 		/* Will leave the LED as it is */
68 		break;
69 	}
70 }
71 EXPORT_SYMBOL(ledtrig_cpu);
72 
73 static int ledtrig_cpu_syscore_suspend(void)
74 {
75 	ledtrig_cpu(CPU_LED_STOP);
76 	return 0;
77 }
78 
79 static void ledtrig_cpu_syscore_resume(void)
80 {
81 	ledtrig_cpu(CPU_LED_START);
82 }
83 
84 static void ledtrig_cpu_syscore_shutdown(void)
85 {
86 	ledtrig_cpu(CPU_LED_HALTED);
87 }
88 
89 static struct syscore_ops ledtrig_cpu_syscore_ops = {
90 	.shutdown	= ledtrig_cpu_syscore_shutdown,
91 	.suspend	= ledtrig_cpu_syscore_suspend,
92 	.resume		= ledtrig_cpu_syscore_resume,
93 };
94 
95 static int ledtrig_cpu_notify(struct notifier_block *self,
96 					   unsigned long action, void *hcpu)
97 {
98 	switch (action & ~CPU_TASKS_FROZEN) {
99 	case CPU_STARTING:
100 		ledtrig_cpu(CPU_LED_START);
101 		break;
102 	case CPU_DYING:
103 		ledtrig_cpu(CPU_LED_STOP);
104 		break;
105 	}
106 
107 	return NOTIFY_OK;
108 }
109 
110 
111 static struct notifier_block ledtrig_cpu_nb = {
112 	.notifier_call = ledtrig_cpu_notify,
113 };
114 
115 static int __init ledtrig_cpu_init(void)
116 {
117 	int cpu;
118 
119 	/* Supports up to 9999 cpu cores */
120 	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
121 
122 	/*
123 	 * Registering CPU led trigger for each CPU core here
124 	 * ignores CPU hotplug, but after this CPU hotplug works
125 	 * fine with this trigger.
126 	 */
127 	for_each_possible_cpu(cpu) {
128 		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
129 
130 		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
131 
132 		led_trigger_register_simple(trig->name, &trig->_trig);
133 	}
134 
135 	register_syscore_ops(&ledtrig_cpu_syscore_ops);
136 	register_cpu_notifier(&ledtrig_cpu_nb);
137 
138 	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
139 
140 	return 0;
141 }
142 device_initcall(ledtrig_cpu_init);
143