ledtrig-cpu.c

  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
 33struct led_trigger_cpu {
 34	bool is_active;
 35	char name[MAX_NAME_LEN];
 36	struct led_trigger *_trig;
 37};
 38
 39static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
 40
 41static struct led_trigger *trig_cpu_all;
 42static 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 */
 51void 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}
 95EXPORT_SYMBOL(ledtrig_cpu);
 96
 97static int ledtrig_cpu_syscore_suspend(void *data)
 98{
 99	ledtrig_cpu(CPU_LED_STOP);
100	return 0;
101}
102
103static void ledtrig_cpu_syscore_resume(void *data)
104{
105	ledtrig_cpu(CPU_LED_START);
106}
107
108static void ledtrig_cpu_syscore_shutdown(void *data)
109{
110	ledtrig_cpu(CPU_LED_HALTED);
111}
112
113static const 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
119static struct syscore ledtrig_cpu_syscore = {
120	.ops = &ledtrig_cpu_syscore_ops,
121};
122
123static int ledtrig_online_cpu(unsigned int cpu)
124{
125	ledtrig_cpu(CPU_LED_START);
126	return 0;
127}
128
129static int ledtrig_prepare_down_cpu(unsigned int cpu)
130{
131	ledtrig_cpu(CPU_LED_STOP);
132	return 0;
133}
134
135static int __init ledtrig_cpu_init(void)
136{
137	unsigned int cpu;
138	int ret;
139
140	/* Supports up to 9999 cpu cores */
141	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
142
143	/*
144	 * Registering a trigger for all CPUs.
145	 */
146	led_trigger_register_simple("cpu", &trig_cpu_all);
147
148	/*
149	 * Registering CPU led trigger for each CPU core here
150	 * ignores CPU hotplug, but after this CPU hotplug works
151	 * fine with this trigger.
152	 */
153	for_each_possible_cpu(cpu) {
154		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
155
156		if (cpu >= 8)
157			continue;
158
159		snprintf(trig->name, MAX_NAME_LEN, "cpu%u", cpu);
160
161		led_trigger_register_simple(trig->name, &trig->_trig);
162	}
163
164	register_syscore(&ledtrig_cpu_syscore);
165
166	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
167				ledtrig_online_cpu, ledtrig_prepare_down_cpu);
168	if (ret < 0)
169		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
170		       ret);
171
172	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
173
174	return 0;
175}
176device_initcall(ledtrig_cpu_init);