[PATCH 02/19] led-triggers: create a trigger for CPU activity

[Bryan Wu <bryan.wu@xxxxxxxxxxxxx>]

Attempting to consolidate the ARM LED code, this removes the
custom RealView LED trigger code to turn LEDs on and off in
response to CPU activity and replace it with a standard trigger.

(bryan.wu@xxxxxxxxxxxxx:
It introduces several syscore stubs into this trigger.
It also provides ledtrig_cpu trigger event stub in <linux/leds.h>.
Although it was inspired by ARM work, it can be used in other arch.)

Cc: Richard Purdie <rpurdie@xxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Bryan Wu <bryan.wu@xxxxxxxxxxxxx>
Reviewed-by: Jamie Iles <jamie@xxxxxxxxxxxxx>
Tested-by: Jochen Friedrich <jochen@xxxxxxxx>
---
 drivers/leds/Kconfig       |   10 +++
 drivers/leds/Makefile      |    1 +
 drivers/leds/ledtrig-cpu.c |  150 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/leds.h       |   16 +++++
 4 files changed, 177 insertions(+)
 create mode 100644 drivers/leds/ledtrig-cpu.c

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 5f12659..dbf8a4c 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -465,6 +465,16 @@ config LEDS_TRIGGER_BACKLIGHT
 
 	  If unsure, say N.
 
+config LEDS_TRIGGER_CPU
+	tristate "LED CPU Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled by active CPUs. This shows
+	  the active CPUs across an array of LEDs so you can see which
+	  CPUs are active on the system at any given moment.
+
+	  If unsure, say N.
+
 config LEDS_TRIGGER_GPIO
 	tristate "LED GPIO Trigger"
 	depends on LEDS_TRIGGERS
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 9475bbb..ea1efb2 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -56,4 +56,5 @@ obj-$(CONFIG_LEDS_TRIGGER_IDE_DISK)	+= ledtrig-ide-disk.o
 obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT)	+= ledtrig-heartbeat.o
 obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT)	+= ledtrig-backlight.o
 obj-$(CONFIG_LEDS_TRIGGER_GPIO)		+= ledtrig-gpio.o
+obj-$(CONFIG_LEDS_TRIGGER_CPU)		+= ledtrig-cpu.o
 obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o
diff --git a/drivers/leds/ledtrig-cpu.c b/drivers/leds/ledtrig-cpu.c
new file mode 100644
index 0000000..1f752e1
--- /dev/null
+++ b/drivers/leds/ledtrig-cpu.c
@@ -0,0 +1,150 @@
+/*
+ * 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@xxxxxxxxxx>
+ * Copyright 2011 - 2012 Bryan Wu <bryan.wu@xxxxxxxxxxxxx>
+ *
+ * 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/module.h>
+#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 "leds.h"
+
+#define MAX_NAME_LEN	8
+
+static DEFINE_PER_CPU(struct led_trigger *, cpu_trig);
+static DEFINE_PER_CPU(char [MAX_NAME_LEN], trig_name);
+static DEFINE_PER_CPU(struct rw_semaphore, trig_lock);
+
+/**
+ * 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
+ * binded LED to turn on or turn off.
+ */
+void ledtrig_cpu(enum cpu_led_event ledevt)
+{
+	struct led_trigger *trig = __get_cpu_var(cpu_trig);
+
+	if (!trig)
+		return;
+
+	/* Locate the correct CPU LED */
+	switch (ledevt) {
+	case CPU_LED_IDLE_END:
+	case CPU_LED_START:
+		/* Will turn the LED on, max brightness */
+		led_trigger_event(trig, LED_FULL);
+		break;
+
+	case CPU_LED_IDLE_START:
+	case CPU_LED_STOP:
+	case CPU_LED_HALTED:
+		/* Will turn the LED off */
+		led_trigger_event(trig, LED_OFF);
+		break;
+
+	default:
+		/* Will leave the LED as it is */
+		break;
+	}
+}
+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 __init ledtrig_cpu_init(void)
+{
+	int cpu;
+
+	/* Supports up to 9999 cpu cores */
+	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
+
+	/*
+	 * 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 *trig;
+		char *name = per_cpu(trig_name, cpu);
+		struct rw_semaphore *lock = &per_cpu(trig_lock, cpu);
+
+		init_rwsem(lock);
+
+		snprintf(name, MAX_NAME_LEN, "cpu%d", cpu);
+
+		down_write(lock);
+		led_trigger_register_simple(name, &trig);
+		per_cpu(cpu_trig, cpu) = trig;
+		up_write(lock);
+	}
+
+	register_syscore_ops(&ledtrig_cpu_syscore_ops);
+
+	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
+
+	return 0;
+}
+module_init(ledtrig_cpu_init);
+
+static void __exit ledtrig_cpu_exit(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct led_trigger *trig = per_cpu(cpu_trig, cpu);
+		char *name = per_cpu(trig_name, cpu);
+
+		led_trigger_unregister_simple(trig);
+		per_cpu(cpu_trig, cpu) = NULL;
+		memset(name, 0, MAX_NAME_LEN);
+	}
+
+	unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
+}
+module_exit(ledtrig_cpu_exit);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@xxxxxxxxxx>");
+MODULE_AUTHOR("Bryan Wu <bryan.wu@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("CPU LED trigger");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 39eee41..aaf88b0 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -212,4 +212,20 @@ struct gpio_led_platform_data {
 struct platform_device *gpio_led_register_device(
 		int id, const struct gpio_led_platform_data *pdata);
 
+enum cpu_led_event {
+	CPU_LED_IDLE_START,	/* CPU enters idle */
+	CPU_LED_IDLE_END,	/* CPU idle ends */
+	CPU_LED_START,		/* Machine starts, especially resume */
+	CPU_LED_STOP,		/* Machine stops, especially suspend */
+	CPU_LED_HALTED,		/* Machine shutdown */
+};
+#if defined(CONFIG_LEDS_TRIGGER_CPU) || defined(CONFIG_LEDS_TRIGGER_CPU_MODULE)
+extern void ledtrig_cpu(enum cpu_led_event evt);
+#else
+static inline void ledtrig_cpu(enum cpu_led_event evt)
+{
+	return;
+}
+#endif
+
 #endif		/* __LINUX_LEDS_H_INCLUDED */
-- 
1.7.9.5

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