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 first 8 CPUs and named
6  * as cpu0..cpu7. There's additional trigger called cpu that
7  * is on when any CPU is active.
8  *
9  * If you want support for arbitrary number of CPUs, make it one trigger,
10  * with additional sysfs file selecting which CPU to watch.
11  *
12  * It can be bound to any LED just like other triggers using either a
13  * board file or via sysfs interface.
14  *
15  * An API named ledtrig_cpu is exported for any user, who want to add CPU
16  * activity indication in their code.
17  *
18  * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
19  * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
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 	bool is_active;
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 static struct led_trigger *trig_cpu_all;
42 static atomic_t num_active_cpus = ATOMIC_INIT(0);
43 
44 /**
45  * ledtrig_cpu - emit a CPU event as a trigger
46  * @evt: CPU event to be emitted
47  *
48  * Emit a CPU event on a CPU core, which will trigger a
49  * bound LED to turn on or turn off.
50  */
51 void ledtrig_cpu(enum cpu_led_event ledevt)
52 {
53 	struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
54 	bool is_active = trig->is_active;
55 
56 	/* Locate the correct CPU LED */
57 	switch (ledevt) {
58 	case CPU_LED_IDLE_END:
59 	case CPU_LED_START:
60 		/* Will turn the LED on, max brightness */
61 		is_active = true;
62 		break;
63 
64 	case CPU_LED_IDLE_START:
65 	case CPU_LED_STOP:
66 	case CPU_LED_HALTED:
67 		/* Will turn the LED off */
68 		is_active = false;
69 		break;
70 
71 	default:
72 		/* Will leave the LED as it is */
73 		break;
74 	}
75 
76 	if (is_active != trig->is_active) {
77 		unsigned int active_cpus;
78 		unsigned int total_cpus;
79 
80 		/* Update trigger state */
81 		trig->is_active = is_active;
82 		atomic_add(is_active ? 1 : -1, &num_active_cpus);
83 		active_cpus = atomic_read(&num_active_cpus);
84 		total_cpus = num_present_cpus();
85 
86 		led_trigger_event(trig->_trig,
87 			is_active ? LED_FULL : LED_OFF);
88 
89 
90 		led_trigger_event(trig_cpu_all,
91 			DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus));
92 
93 	}
94 }
95 EXPORT_SYMBOL(ledtrig_cpu);
96 
97 static int ledtrig_cpu_syscore_suspend(void)
98 {
99 	ledtrig_cpu(CPU_LED_STOP);
100 	return 0;
101 }
102 
103 static void ledtrig_cpu_syscore_resume(void)
104 {
105 	ledtrig_cpu(CPU_LED_START);
106 }
107 
108 static void ledtrig_cpu_syscore_shutdown(void)
109 {
110 	ledtrig_cpu(CPU_LED_HALTED);
111 }
112 
113 static struct syscore_ops ledtrig_cpu_syscore_ops = {
114 	.shutdown	= ledtrig_cpu_syscore_shutdown,
115 	.suspend	= ledtrig_cpu_syscore_suspend,
116 	.resume		= ledtrig_cpu_syscore_resume,
117 };
118 
119 static int ledtrig_online_cpu(unsigned int cpu)
120 {
121 	ledtrig_cpu(CPU_LED_START);
122 	return 0;
123 }
124 
125 static int ledtrig_prepare_down_cpu(unsigned int cpu)
126 {
127 	ledtrig_cpu(CPU_LED_STOP);
128 	return 0;
129 }
130 
131 static int __init ledtrig_cpu_init(void)
132 {
133 	int cpu;
134 	int ret;
135 
136 	/* Supports up to 9999 cpu cores */
137 	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
138 
139 	/*
140 	 * Registering a trigger for all CPUs.
141 	 */
142 	led_trigger_register_simple("cpu", &trig_cpu_all);
143 
144 	/*
145 	 * Registering CPU led trigger for each CPU core here
146 	 * ignores CPU hotplug, but after this CPU hotplug works
147 	 * fine with this trigger.
148 	 */
149 	for_each_possible_cpu(cpu) {
150 		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
151 
152 		if (cpu >= 8)
153 			continue;
154 
155 		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
156 
157 		led_trigger_register_simple(trig->name, &trig->_trig);
158 	}
159 
160 	register_syscore_ops(&ledtrig_cpu_syscore_ops);
161 
162 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
163 				ledtrig_online_cpu, ledtrig_prepare_down_cpu);
164 	if (ret < 0)
165 		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
166 		       ret);
167 
168 	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
169 
170 	return 0;
171 }
172 device_initcall(ledtrig_cpu_init);
173