1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * ledtrig-cpu.c - LED trigger based on CPU activity
4  *
5  * This LED trigger will be registered for each possible CPU and named as
6  * cpu0, cpu1, cpu2, cpu3, etc.
7  *
8  * It can be bound to any LED just like other triggers using either a
9  * board file or via sysfs interface.
10  *
11  * An API named ledtrig_cpu is exported for any user, who want to add CPU
12  * activity indication in their code
13  *
14  * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
15  * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
16  */
17 
18 #include <linux/kernel.h>
19 #include <linux/init.h>
20 #include <linux/slab.h>
21 #include <linux/percpu.h>
22 #include <linux/syscore_ops.h>
23 #include <linux/rwsem.h>
24 #include <linux/cpu.h>
25 #include "../leds.h"
26 
27 #define MAX_NAME_LEN	8
28 
29 struct led_trigger_cpu {
30 	bool is_active;
31 	char name[MAX_NAME_LEN];
32 	struct led_trigger *_trig;
33 };
34 
35 static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
36 
37 static struct led_trigger *trig_cpu_all;
38 static atomic_t num_active_cpus = ATOMIC_INIT(0);
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  * bound 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 	bool is_active = trig->is_active;
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 		is_active = true;
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 		is_active = false;
65 		break;
66 
67 	default:
68 		/* Will leave the LED as it is */
69 		break;
70 	}
71 
72 	if (is_active != trig->is_active) {
73 		unsigned int active_cpus;
74 		unsigned int total_cpus;
75 
76 		/* Update trigger state */
77 		trig->is_active = is_active;
78 		atomic_add(is_active ? 1 : -1, &num_active_cpus);
79 		active_cpus = atomic_read(&num_active_cpus);
80 		total_cpus = num_present_cpus();
81 
82 		led_trigger_event(trig->_trig,
83 			is_active ? LED_FULL : LED_OFF);
84 
85 
86 		led_trigger_event(trig_cpu_all,
87 			DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus));
88 
89 	}
90 }
91 EXPORT_SYMBOL(ledtrig_cpu);
92 
93 static int ledtrig_cpu_syscore_suspend(void)
94 {
95 	ledtrig_cpu(CPU_LED_STOP);
96 	return 0;
97 }
98 
99 static void ledtrig_cpu_syscore_resume(void)
100 {
101 	ledtrig_cpu(CPU_LED_START);
102 }
103 
104 static void ledtrig_cpu_syscore_shutdown(void)
105 {
106 	ledtrig_cpu(CPU_LED_HALTED);
107 }
108 
109 static struct syscore_ops ledtrig_cpu_syscore_ops = {
110 	.shutdown	= ledtrig_cpu_syscore_shutdown,
111 	.suspend	= ledtrig_cpu_syscore_suspend,
112 	.resume		= ledtrig_cpu_syscore_resume,
113 };
114 
115 static int ledtrig_online_cpu(unsigned int cpu)
116 {
117 	ledtrig_cpu(CPU_LED_START);
118 	return 0;
119 }
120 
121 static int ledtrig_prepare_down_cpu(unsigned int cpu)
122 {
123 	ledtrig_cpu(CPU_LED_STOP);
124 	return 0;
125 }
126 
127 static int __init ledtrig_cpu_init(void)
128 {
129 	int cpu;
130 	int ret;
131 
132 	/* Supports up to 9999 cpu cores */
133 	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
134 
135 	/*
136 	 * Registering a trigger for all CPUs.
137 	 */
138 	led_trigger_register_simple("cpu", &trig_cpu_all);
139 
140 	/*
141 	 * Registering CPU led trigger for each CPU core here
142 	 * ignores CPU hotplug, but after this CPU hotplug works
143 	 * fine with this trigger.
144 	 */
145 	for_each_possible_cpu(cpu) {
146 		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
147 
148 		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
149 
150 		led_trigger_register_simple(trig->name, &trig->_trig);
151 	}
152 
153 	register_syscore_ops(&ledtrig_cpu_syscore_ops);
154 
155 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
156 				ledtrig_online_cpu, ledtrig_prepare_down_cpu);
157 	if (ret < 0)
158 		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
159 		       ret);
160 
161 	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
162 
163 	return 0;
164 }
165 device_initcall(ledtrig_cpu_init);
166