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 * @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 */ 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 unsigned 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%u", 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); 173