LXR linux/drivers/leds/trigger/ledtrig-cpu.c

   1/*
   2 * ledtrig-cpu.c - LED trigger based on CPU activity
   3 *
   4 * This LED trigger will be registered for each possible CPU and named as
   5 * cpu0, cpu1, cpu2, cpu3, etc.
   6 *
   7 * It can be bound to any LED just like other triggers using either a
   8 * board file or via sysfs interface.
   9 *
  10 * An API named ledtrig_cpu is exported for any user, who want to add CPU
  11 * activity indication in their code
  12 *
  13 * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
  14 * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
  15 *
  16 * This program is free software; you can redistribute it and/or modify
  17 * it under the terms of the GNU General Public License version 2 as
  18 * published by the Free Software Foundation.
  19 *
  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 * @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 */
  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)
  98{
  99        ledtrig_cpu(CPU_LED_STOP);
 100        return 0;
 101}
 102
 103static void ledtrig_cpu_syscore_resume(void)
 104{
 105        ledtrig_cpu(CPU_LED_START);
 106}
 107
 108static void ledtrig_cpu_syscore_shutdown(void)
 109{
 110        ledtrig_cpu(CPU_LED_HALTED);
 111}
 112
 113static 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 int ledtrig_online_cpu(unsigned int cpu)
 120{
 121        ledtrig_cpu(CPU_LED_START);
 122        return 0;
 123}
 124
 125static int ledtrig_prepare_down_cpu(unsigned int cpu)
 126{
 127        ledtrig_cpu(CPU_LED_STOP);
 128        return 0;
 129}
 130
 131static 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                snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
 153
 154                led_trigger_register_simple(trig->name, &trig->_trig);
 155        }
 156
 157        register_syscore_ops(&ledtrig_cpu_syscore_ops);
 158
 159        ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
 160                                ledtrig_online_cpu, ledtrig_prepare_down_cpu);
 161        if (ret < 0)
 162                pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
 163                       ret);
 164
 165        pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
 166
 167        return 0;
 168}
 169device_initcall(ledtrig_cpu_init);
 170