struct dev_pm_ops {....int (*runtime_suspend)(struct device *dev);int (*runtime_resume)(struct device *dev);int (*runtime_idle)(struct device *dev);
};

三个回调函数分别用于suspend device，resume device和idle device。通常Runtime PM framework会在合适的时机调用三个函数。

enum rpm_status {RPM_ACTIVE = 0,RPM_RESUMING,RPM_SUSPENDED,RPM_SUSPENDING,
};

RPM_ACTIVE:                设备处于正常工作状态，处于全速全进状态。runtime_resume的回调执行完毕。

enum rpm_request {RPM_REQ_NONE = 0,RPM_REQ_IDLE,RPM_REQ_SUSPEND,RPM_REQ_AUTOSUSPEND,RPM_REQ_RESUME,
};

PRM_REQ_NONE:                        Do nothing

Runtime PM数据段

struct dev_pm_info {....struct timer_list   suspend_timer;unsigned long     timer_expires;struct work_struct    work;wait_queue_head_t  wait_queue;atomic_t     usage_count;atomic_t        child_count;unsigned int        disable_depth:3;unsigned int        idle_notification:1;unsigned int        request_pending:1;unsigned int      deferred_resume:1;unsigned int      run_wake:1;unsigned int     runtime_auto:1;unsigned int     no_callbacks:1;unsigned int     irq_safe:1;unsigned int     use_autosuspend:1;unsigned int      timer_autosuspends:1;unsigned int       memalloc_noio:1;enum rpm_request    request;enum rpm_status     runtime_status;int          runtime_error;int           autosuspend_delay;unsigned long     last_busy;unsigned long     active_jiffies;unsigned long        suspended_jiffies;unsigned long     accounting_timestamp;};

.suspend_timer:          休眠时候用到的定时器。

Runtime PM运行机制

Runtime PM回调约束

    if (pm_runtime_callbacks_present(dev)) {rc = sysfs_merge_group(&dev->kobj, &pm_runtime_attr_group);if (rc)goto err_out;}

runtime的属性如下：

static struct attribute *runtime_attrs[] = {
#ifdef CONFIG_PM_RUNTIME
#ifndef CONFIG_PM_ADVANCED_DEBUG&dev_attr_runtime_status.attr,
#endif&dev_attr_control.attr,&dev_attr_runtime_suspended_time.attr,&dev_attr_runtime_active_time.attr,&dev_attr_autosuspend_delay_ms.attr,
#endif /* CONFIG_PM_RUNTIME */NULL,
};

其中有五个属性。分别为control,  runtime_susupend_time,  runtime_active_time,  autosuspend_delay_ms，runtime_status属性。

• pm_runtime_enable(使能设备的runtime pm)

void pm_runtime_enable(struct device *dev)
{unsigned long flags;spin_lock_irqsave(&dev->power.lock, flags);if (dev->power.disable_depth > 0)dev->power.disable_depth--;elsedev_warn(dev, "Unbalanced %s!\n", __func__);spin_unlock_irqrestore(&dev->power.lock, flags);
}

• __pm_runtime_resume(resume设备)

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/pm_runtime.h>static int runtime_pm_probe(struct platform_device *pdev)
{printk(KERN_EMERG "runtime_pm: runtime_pm_probe!\n");pm_runtime_set_active(&pdev->dev);pm_runtime_enable(&pdev->dev);  return 0;
}static int runtime_pm_remove(struct platform_device *pdev)
{printk(KERN_EMERG "runtime_pm: runtime_pm_remove!\n");pm_runtime_disable(&pdev->dev);return 0;
}static int runtime_pm_suspend(struct device *dev)
{printk(KERN_EMERG "runtime_pm: runtime_pm_suspend!\n");return 0;
}static int runtime_pm_resume(struct device *dev)
{printk(KERN_EMERG "runtime_pm: runtime_pm_resume!\n");return 0;
}static int runtime_pm_idle(struct device *dev)
{printk(KERN_EMERG "runtime_pm: runtime_pm_idle\n");return 0;
}static const struct dev_pm_ops runtime_pm_ops = {SET_RUNTIME_PM_OPS(runtime_pm_suspend,runtime_pm_resume,runtime_pm_idle)
};static void runtime_pm_release(struct device * dev)
{
}static struct platform_device runtime_device = {.name     = "runtime_device",.id         = -1,.dev        = {.release = runtime_pm_release,},
};static struct platform_driver runtime_driver = {.probe       = runtime_pm_probe,.remove     = runtime_pm_remove,.driver        = {.owner  = THIS_MODULE,.name    = "runtime_device",.pm   = &runtime_pm_ops,},
};static int runtime_pm_init(void)
{   printk(KERN_EMERG "runtime_pm: runtime_pm_init\n");platform_device_register(&runtime_device);platform_driver_register(&runtime_driver);return 0;
}static void runtime_pm_exit(void)
{printk(KERN_EMERG "runtime_pm: runtime_pm_exit\n");platform_driver_unregister(&runtime_driver);platform_device_unregister(&runtime_device);
}module_init(runtime_pm_init);
module_exit(runtime_pm_exit);
MODULE_LICENSE("GPL");

如下是测试结果：

cat /sys/devices/platform/runtime_device/power/runtime_status
suspend

2. 查看设备的runtime_suspend时间

cat /sys/devices/platform/runtime_device/power/runtime_suspended_time
341028

3. 使设备处于active状态

echo on >  /sys/devices/platform/runtime_device/power/control

4. 使设备进入suspend状态

echo auto > /sys/devices/platform/runtime_device/power/control

5. 查看转换状态的打印

test:/ # dmesg | grep "runtime"
[  451.432602] c7 runtime_pm: runtime_pm_resume!
[  509.842328] c5 runtime_pm: runtime_pm_idle
[  509.846430] c5 runtime_pm: runtime_pm_suspend!