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_online_cpu(unsigned int cpu)
96 {
97 	ledtrig_cpu(CPU_LED_START);
98 	return 0;
99 }
100 
101 static int ledtrig_prepare_down_cpu(unsigned int cpu)
102 {
103 	ledtrig_cpu(CPU_LED_STOP);
104 	return 0;
105 }
106 
107 static int __init ledtrig_cpu_init(void)
108 {
109 	int cpu;
110 	int ret;
111 
112 	/* Supports up to 9999 cpu cores */
113 	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
114 
115 	/*
116 	 * Registering CPU led trigger for each CPU core here
117 	 * ignores CPU hotplug, but after this CPU hotplug works
118 	 * fine with this trigger.
119 	 */
120 	for_each_possible_cpu(cpu) {
121 		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
122 
123 		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
124 
125 		led_trigger_register_simple(trig->name, &trig->_trig);
126 	}
127 
128 	register_syscore_ops(&ledtrig_cpu_syscore_ops);
129 
130 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_LEDTRIG_STARTING",
131 				ledtrig_online_cpu, ledtrig_prepare_down_cpu);
132 	if (ret < 0)
133 		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
134 		       ret);
135 
136 	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
137 
138 	return 0;
139 }
140 device_initcall(ledtrig_cpu_init);
141