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); 166