drivers/leds/trigger/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
  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  * @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  */
  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
  97 static int ledtrig_cpu_syscore_suspend(void)
  98 {
  99         ledtrig_cpu(CPU_LED_STOP);
 100         return 0;
 101 }
 102
 103 static void ledtrig_cpu_syscore_resume(void)
 104 {
 105         ledtrig_cpu(CPU_LED_START);
 106 }
 107
 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
 119 static int ledtrig_online_cpu(unsigned int cpu)
 120 {
 121         ledtrig_cpu(CPU_LED_START);
 122         return 0;
 123 }
 124
 125 static int ledtrig_prepare_down_cpu(unsigned int cpu)
 126 {
 127         ledtrig_cpu(CPU_LED_STOP);
 128         return 0;
 129 }
 130
 131 static 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                 if (cpu >= 8)
 153                         continue;
 154
 155                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", 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);