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 
34 struct led_trigger_cpu {
35 	char name[MAX_NAME_LEN];
36 	struct led_trigger *_trig;
37 };
38 
39 static 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  */
48 void 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 }
72 EXPORT_SYMBOL(ledtrig_cpu);
73 
74 static int ledtrig_cpu_syscore_suspend(void)
75 {
76 	ledtrig_cpu(CPU_LED_STOP);
77 	return 0;
78 }
79 
80 static void ledtrig_cpu_syscore_resume(void)
81 {
82 	ledtrig_cpu(CPU_LED_START);
83 }
84 
85 static void ledtrig_cpu_syscore_shutdown(void)
86 {
87 	ledtrig_cpu(CPU_LED_HALTED);
88 }
89 
90 static 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 
96 static 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 
112 static struct notifier_block ledtrig_cpu_nb = {
113 	.notifier_call = ledtrig_cpu_notify,
114 };
115 
116 static 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 }
143 module_init(ledtrig_cpu_init);
144 
145 static 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 }
161 module_exit(ledtrig_cpu_exit);
162 
163 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
164 MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
165 MODULE_DESCRIPTION("CPU LED trigger");
166 MODULE_LICENSE("GPL");
167