1 // SPDX-License-Identifier: GPL-2.0-only
3 * ledtrig-cpu.c - LED trigger based on CPU activity
5 * This LED trigger will be registered for each possible CPU and named as
6 * cpu0, cpu1, cpu2, cpu3, etc.
8 * It can be bound to any LED just like other triggers using either a
9 * board file or via sysfs interface.
11 * An API named ledtrig_cpu is exported for any user, who want to add CPU
12 * activity indication in their code
14 * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
15 * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
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>
27 #define MAX_NAME_LEN 8
29 struct led_trigger_cpu
{
31 char name
[MAX_NAME_LEN
];
32 struct led_trigger
*_trig
;
35 static DEFINE_PER_CPU(struct led_trigger_cpu
, cpu_trig
);
37 static struct led_trigger
*trig_cpu_all
;
38 static atomic_t num_active_cpus
= ATOMIC_INIT(0);
41 * ledtrig_cpu - emit a CPU event as a trigger
42 * @evt: CPU event to be emitted
44 * Emit a CPU event on a CPU core, which will trigger a
45 * bound LED to turn on or turn off.
47 void ledtrig_cpu(enum cpu_led_event ledevt
)
49 struct led_trigger_cpu
*trig
= this_cpu_ptr(&cpu_trig
);
50 bool is_active
= trig
->is_active
;
52 /* Locate the correct CPU LED */
54 case CPU_LED_IDLE_END
:
56 /* Will turn the LED on, max brightness */
60 case CPU_LED_IDLE_START
:
63 /* Will turn the LED off */
68 /* Will leave the LED as it is */
72 if (is_active
!= trig
->is_active
) {
73 unsigned int active_cpus
;
74 unsigned int total_cpus
;
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();
82 led_trigger_event(trig
->_trig
,
83 is_active
? LED_FULL
: LED_OFF
);
86 led_trigger_event(trig_cpu_all
,
87 DIV_ROUND_UP(LED_FULL
* active_cpus
, total_cpus
));
91 EXPORT_SYMBOL(ledtrig_cpu
);
93 static int ledtrig_cpu_syscore_suspend(void)
95 ledtrig_cpu(CPU_LED_STOP
);
99 static void ledtrig_cpu_syscore_resume(void)
101 ledtrig_cpu(CPU_LED_START
);
104 static void ledtrig_cpu_syscore_shutdown(void)
106 ledtrig_cpu(CPU_LED_HALTED
);
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
,
115 static int ledtrig_online_cpu(unsigned int cpu
)
117 ledtrig_cpu(CPU_LED_START
);
121 static int ledtrig_prepare_down_cpu(unsigned int cpu
)
123 ledtrig_cpu(CPU_LED_STOP
);
127 static int __init
ledtrig_cpu_init(void)
132 /* Supports up to 9999 cpu cores */
133 BUILD_BUG_ON(CONFIG_NR_CPUS
> 9999);
136 * Registering a trigger for all CPUs.
138 led_trigger_register_simple("cpu", &trig_cpu_all
);
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.
145 for_each_possible_cpu(cpu
) {
146 struct led_trigger_cpu
*trig
= &per_cpu(cpu_trig
, cpu
);
148 snprintf(trig
->name
, MAX_NAME_LEN
, "cpu%d", cpu
);
150 led_trigger_register_simple(trig
->name
, &trig
->_trig
);
153 register_syscore_ops(&ledtrig_cpu_syscore_ops
);
155 ret
= cpuhp_setup_state(CPUHP_AP_ONLINE_DYN
, "leds/trigger:starting",
156 ledtrig_online_cpu
, ledtrig_prepare_down_cpu
);
158 pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
161 pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
165 device_initcall(ledtrig_cpu_init
);