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 * @ledevt: 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 */
ledtrig_cpu(enum cpu_led_event ledevt)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
ledtrig_cpu_syscore_suspend(void)97 static int ledtrig_cpu_syscore_suspend(void)
98 {
99 ledtrig_cpu(CPU_LED_STOP);
100 return 0;
101 }
102
ledtrig_cpu_syscore_resume(void)103 static void ledtrig_cpu_syscore_resume(void)
104 {
105 ledtrig_cpu(CPU_LED_START);
106 }
107
ledtrig_cpu_syscore_shutdown(void)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
ledtrig_online_cpu(unsigned int cpu)119 static int ledtrig_online_cpu(unsigned int cpu)
120 {
121 ledtrig_cpu(CPU_LED_START);
122 return 0;
123 }
124
ledtrig_prepare_down_cpu(unsigned int cpu)125 static int ledtrig_prepare_down_cpu(unsigned int cpu)
126 {
127 ledtrig_cpu(CPU_LED_STOP);
128 return 0;
129 }
130
ledtrig_cpu_init(void)131 static int __init ledtrig_cpu_init(void)
132 {
133 unsigned 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%u", 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