linux-stable/drivers/leds/trigger/ledtrig-cpu.c
Paulo Costa 0b88b71c77 leds/trigger/cpu: Add LED trigger for all CPUs aggregated
Currently there is one CPU led trigger per cpu ('cpu0', 'cpu1', ...)

This patch adds a new trigger, 'cpu', with brightness proportional to
the number of active CPUs.

If multiple brightness levels aren't supported on the LED,
it effectively indicates if there is any CPU active.

This is particularly useful on tiny linux boards with more CPU cores than LED pins.

Signed-off-by: Paulo Costa <me@paulo.costa.nom.br>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
2017-03-06 22:06:47 +01:00

169 lines
3.9 KiB
C

/*
* ledtrig-cpu.c - LED trigger based on CPU activity
*
* This LED trigger will be registered for each possible CPU and named as
* cpu0, cpu1, cpu2, cpu3, etc.
*
* It can be bound to any LED just like other triggers using either a
* board file or via sysfs interface.
*
* An API named ledtrig_cpu is exported for any user, who want to add CPU
* activity indication in their code
*
* Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
* Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/percpu.h>
#include <linux/syscore_ops.h>
#include <linux/rwsem.h>
#include <linux/cpu.h>
#include "../leds.h"
#define MAX_NAME_LEN 8
struct led_trigger_cpu {
bool is_active;
char name[MAX_NAME_LEN];
struct led_trigger *_trig;
};
static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
static struct led_trigger *trig_cpu_all;
static atomic_t num_active_cpus = ATOMIC_INIT(0);
/**
* ledtrig_cpu - emit a CPU event as a trigger
* @evt: CPU event to be emitted
*
* Emit a CPU event on a CPU core, which will trigger a
* bound LED to turn on or turn off.
*/
void ledtrig_cpu(enum cpu_led_event ledevt)
{
struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
bool is_active = trig->is_active;
/* Locate the correct CPU LED */
switch (ledevt) {
case CPU_LED_IDLE_END:
case CPU_LED_START:
/* Will turn the LED on, max brightness */
is_active = true;
break;
case CPU_LED_IDLE_START:
case CPU_LED_STOP:
case CPU_LED_HALTED:
/* Will turn the LED off */
is_active = false;
break;
default:
/* Will leave the LED as it is */
break;
}
if (is_active != trig->is_active) {
unsigned int active_cpus;
unsigned int total_cpus;
/* Update trigger state */
trig->is_active = is_active;
atomic_add(is_active ? 1 : -1, &num_active_cpus);
active_cpus = atomic_read(&num_active_cpus);
total_cpus = num_present_cpus();
led_trigger_event(trig->_trig,
is_active ? LED_FULL : LED_OFF);
led_trigger_event(trig_cpu_all,
DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus));
}
}
EXPORT_SYMBOL(ledtrig_cpu);
static int ledtrig_cpu_syscore_suspend(void)
{
ledtrig_cpu(CPU_LED_STOP);
return 0;
}
static void ledtrig_cpu_syscore_resume(void)
{
ledtrig_cpu(CPU_LED_START);
}
static void ledtrig_cpu_syscore_shutdown(void)
{
ledtrig_cpu(CPU_LED_HALTED);
}
static struct syscore_ops ledtrig_cpu_syscore_ops = {
.shutdown = ledtrig_cpu_syscore_shutdown,
.suspend = ledtrig_cpu_syscore_suspend,
.resume = ledtrig_cpu_syscore_resume,
};
static int ledtrig_online_cpu(unsigned int cpu)
{
ledtrig_cpu(CPU_LED_START);
return 0;
}
static int ledtrig_prepare_down_cpu(unsigned int cpu)
{
ledtrig_cpu(CPU_LED_STOP);
return 0;
}
static int __init ledtrig_cpu_init(void)
{
int cpu;
int ret;
/* Supports up to 9999 cpu cores */
BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
/*
* Registering a trigger for all CPUs.
*/
led_trigger_register_simple("cpu", &trig_cpu_all);
/*
* Registering CPU led trigger for each CPU core here
* ignores CPU hotplug, but after this CPU hotplug works
* fine with this trigger.
*/
for_each_possible_cpu(cpu) {
struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
led_trigger_register_simple(trig->name, &trig->_trig);
}
register_syscore_ops(&ledtrig_cpu_syscore_ops);
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
ledtrig_online_cpu, ledtrig_prepare_down_cpu);
if (ret < 0)
pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
ret);
pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
return 0;
}
device_initcall(ledtrig_cpu_init);