root/drivers/leds/trigger/ledtrig-cpu.c

DEFINITIONS

1. ledtrig_cpu
2. ledtrig_cpu_syscore_suspend
3. ledtrig_cpu_syscore_resume
4. ledtrig_cpu_syscore_shutdown
5. ledtrig_online_cpu
6. ledtrig_prepare_down_cpu
7. ledtrig_cpu_init

   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);