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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);