linux内核演进中设备驱动关于电源管理方式的变更

转自http://blog.csdn.net/lizhiguo0532/article/details/6453567

The suspend/resume will not be called if they are defined in
device_driver directly,
PM core will only use suspend/resume function in dev_pm_ops. Thus we shall
mark the old suspend/resume deprecated and make them scheduled for removal.

新版linux系统设备架构中关于电源管理方式的变更
based on linux-2.6.32 

一、设备模型各数据结构中电源管理的部分

  linux的设备模型通过诸多结构体来联合描述，如struct device，struct device_type，struct class，struct device_driver，struct bus_type等。  
  @kernel/include/linux/devices.h中有这几中结构体的定义，这里只列出和PM有关的项，其余查看源码：

  struct device{   ...   struct dev_pm_info power;    ...  }    struct device_type {   ...   int (*uevent)(struct device *dev, struct kobj_uevent_env *env);   char *(*devnode)(struct device *dev, mode_t *mode);   void (*release)(struct device *dev);     const struct dev_pm_ops *pm;  };    struct class {   ...   void (*class_release)(struct class *class);   void (*dev_release)(struct device *dev);     int (*suspend)(struct device *dev, pm_message_t state);   int (*resume)(struct device *dev);     const struct dev_pm_ops *pm;   ...  };   struct device_driver {   ...   int (*probe) (struct device *dev);   int (*remove) (struct device *dev);   void (*shutdown) (struct device *dev);   int (*suspend) (struct device *dev, pm_message_t state);   int (*resume) (struct device *dev);     const struct dev_pm_ops *pm;   ...  };    struct bus_type {   ...   int (*match)(struct device *dev, struct device_driver *drv);   int (*uevent)(struct device *dev, struct kobj_uevent_env *env);   int (*probe)(struct device *dev);   int (*remove)(struct device *dev);   void (*shutdown)(struct device *dev);     int (*suspend)(struct device *dev, pm_message_t state);   int (*resume)(struct device *dev);   const struct dev_pm_ops *pm;   ...  };

  以上可以看出和电源管理相关的两个结构体是struct dev_pm_info和struct dev_pm_ops，他们定义于文件
  @kernel/include/linux/pm.h

  struct dev_pm_info {   pm_message_t  power_state;   unsigned int  can_wakeup:1;   unsigned int  should_wakeup:1;   enum dpm_state  status;  /* Owned by the PM core - 表示该设备当前的PM状态*/  #ifdef CONFIG_PM_SLEEP   struct list_head entry;  /* 链接到dpm_list全局链表中的连接体 */  #endif  #ifdef CONFIG_PM_RUNTIME   // undef   struct timer_list suspend_timer;   unsigned long  timer_expires;   struct work_struct work;   wait_queue_head_t wait_queue;   spinlock_t  lock;   atomic_t  usage_count;   atomic_t  child_count;   unsigned int  disable_depth:3;   unsigned int  ignore_children:1;   unsigned int  idle_notification:1;   unsigned int  request_pending:1;   unsigned int  deferred_resume:1;   enum rpm_request request;   enum rpm_status  runtime_status;   int   runtime_error;  #endif  };    struct dev_pm_ops {   int (*prepare)(struct device *dev);   void (*complete)(struct device *dev);   int (*suspend)(struct device *dev);   int (*resume)(struct device *dev);   int (*freeze)(struct device *dev);   int (*thaw)(struct device *dev);   int (*poweroff)(struct device *dev);   int (*restore)(struct device *dev);   int (*suspend_noirq)(struct device *dev);   int (*resume_noirq)(struct device *dev);   int (*freeze_noirq)(struct device *dev);   int (*thaw_noirq)(struct device *dev);   int (*poweroff_noirq)(struct device *dev);   int (*restore_noirq)(struct device *dev);   int (*runtime_suspend)(struct device *dev);   int (*runtime_resume)(struct device *dev);   int (*runtime_idle)(struct device *dev);  };

二、device中的dev_pm_info结构体

  device结构体中的power项用来将该设备纳入电源管理的范围，记录电源管理的一些信息。
  在注册设备的时候调用函数device_add()来向sysfs系统添加power接口和注册进电源管理系统，代码片段如下：

  ...  error = dpm_sysfs_add(dev);  @kernel/drivers/base/power/sysfs.c  if (error)   goto DPMError;  device_pm_add(dev);      @kernel/drivers/base/power/main.c  ...

  其中dpm_sysfs_add()函数用来向sysfs文件系统中添加相应设备的power接口文件，如注册mt6516_tpd paltform device的时候，会在sysfs中出现如下目录和文件：

  #pwd  /sys/devices/platform/mt6516-tpd  #cd mt6516-tpd  #ls -l  -rw-r--r-- root     root         4096 2010-01-02 06:35 uevent  -r--r--r-- root     root         4096 2010-01-02 06:39 modalias  lrwxrwxrwx root     root              2010-01-02 06:39 subsystem -> ../../../bus/platform  drwxr-xr-x root     root              2010-01-02 06:35 power  lrwxrwxrwx root     root              2010-01-02 06:39 driver -> ../../../bus/platform/drivers/mt6516-tpd  #cd power  #ls -l  -rw-r--r-- root     root         4096 2010-01-02 06:39 wakeup

  源码片段：

  static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);  static struct attribute * power_attrs[] = {   &dev_attr_wakeup.attr,   NULL,  };  static struct attribute_group pm_attr_group = {   .name = "power",  // attribute_group结构体的name域不为NULL的话，都会已name建立一个属性目录的   .attrs = power_attrs,  };    int dpm_sysfs_add(struct device * dev)  {   return sysfs_create_group(&dev->kobj, &pm_attr_group); //在当前device的kobject结构体对应的目录下建立  }

  其中的device_pm_add()函数会将该设备插入到电源管理的核心链表dpm_list中统一管理。
  值得一提的是，在函数device_initialize()会调用函数device_pm_init()来初始化该device结构体的power域：

 dev->power.status = DPM_ON;

  void device_pm_add(struct device *dev)  {   ...   mutex_lock(&dpm_list_mtx);   if (dev->parent) {    if (dev->parent->power.status >= DPM_SUSPENDING)      // 如果某设备处于DPM_SUSPENDING极其之后的状态，此时不允许以该设备为父设备注册子设备     dev_warn(dev, "parent %s should not be sleeping/n", dev_name(dev->parent));   } else if (transition_started) { // transition_started全局变量包含在PM transition期间不允许注册设备    /*     * We refuse to register parentless devices while a PM     * transition is in progress in order to avoid leaving them     * unhandled down the road     */    dev_WARN(dev, "Parentless device registered during a PM transaction/n");   }     list_add_tail(&dev->power.entry, &dpm_list); // 将device结构体通过power.entry项链接进dpm_list   mutex_unlock(&dpm_list_mtx);  }    void device_pm_remove(struct device *dev)  {   ...   mutex_lock(&dpm_list_mtx);   list_del_init(&dev->power.entry);   mutex_unlock(&dpm_list_mtx);   pm_runtime_remove(dev);  }

  举例说明：
  
  我们熟知的platform bus在系统中也是作为一种设备注册进了系统，在sysfs文件系统中的位置是：
  /sys/devices/platform。使用函数device_register(&platform_bus)进行注册，调用device_add()函数，
  注册ok之后，也会出现目录/sys/devices/platform/power。最后也会将其添加进dpm_list中。
  
  i2c控制器外设代表的设备是注册在platform总线上的，也就是说它的父设备是platform。
  最终在platform_device_add()中会调用函数device_add()函数来添加设备，最终也会在mt6516-i2c.0/
  mt6516-i2c.1/mt6516-i2c.2中出现一个power目录，同时这3个platform设备会依靠
  platform_device.dev.power.entry连接件链接到电源管理核心链表dpm_list中。
  /sys/devices/platform/mt6516-i2c.2/power
  
  每一个i2c控制器都会在系统中至少注册成一个适配器(adapter),该结构体将会间接提供给i2c设备的驱动来使用，以避免直接使用i2c控制器结构体。这个适配器没有对应的driver，在错综复杂的i2c架构中，相对于只起到了一个承上启下的作用，上接i2c控制器的结构体及driver，下接i2c设备的结构体i2c_client和特点的driver。adapter.dev.parent为i2c控制器对应的device，所以就会出现名为i2c-0/1/2的设备kobject，只是该设备的bus总线和device_type是：
  adap->dev.bus = &i2c_bus_type;
  adap->dev.type = &i2c_adapter_type;
  然后调用函数device_register(&adap->dev);来注册这个device，所以在对应的i2c-0/1/2目录下也会出现power目录。
  /sys/devices/platform/mt6516-i2c.2/i2c-2/power
  
  i2c设备会通过自动检测或者事先静态描述的方式来注册进系统，不管什么方式，都会调用到函数：i2c_new_device()

  struct i2c_client *client;  client->dev.parent = &client->adapter->dev;  client->dev.bus = &i2c_bus_type;  client->dev.type = &i2c_client_type;  dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap), client->addr);  status = device_register(&client->dev);

  可以看得出来名字是什么了，例如：2-00aa

  #ls -l /sys/devices/platform/mt6516-i2c.2/i2c-2/2-00aa  -rw-r--r-- root     root         4096 2010-01-02 06:35 uevent  -r--r--r-- root     root         4096 2010-01-02 06:38 name  -r--r--r-- root     root         4096 2010-01-02 06:38 modalias  lrwxrwxrwx root     root              2010-01-02 06:38 subsystem -> ../../../../../bus/i2c  drwxr-xr-x root     root              2010-01-02 06:35 power  lrwxrwxrwx root     root              2010-01-02 06:38 driver -> ../../../../../bus/i2c/drivers/mt6516-tpd

三、bus_type、device_driver、device_type、class中的dev_pm_ops方法结构体
  在新的linux内核中，已不再有subsystem数据结构了，他的功能被kset代替。
  
  全局变量bus_kset初始化：kernel_init()-->do_basic_setup()-->driver_init()-->buses_init()
  bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
  
  1. 总线类型结构体：bus_type，以platform和i2c总线为例：

  @kernel/drivers/base/platform.c  static const struct dev_pm_ops platform_dev_pm_ops = {   .prepare = platform_pm_prepare,   //    .complete = platform_pm_complete,  //   .suspend = platform_pm_suspend,   //   .resume = platform_pm_resume,    //   .freeze = platform_pm_freeze,   .thaw = platform_pm_thaw,   .poweroff = platform_pm_poweroff,  //   .restore = platform_pm_restore,   .suspend_noirq = platform_pm_suspend_noirq,   .resume_noirq = platform_pm_resume_noirq,   .freeze_noirq = platform_pm_freeze_noirq,   .thaw_noirq = platform_pm_thaw_noirq,   .poweroff_noirq = platform_pm_poweroff_noirq,   .restore_noirq = platform_pm_restore_noirq,   .runtime_suspend = platform_pm_runtime_suspend,   .runtime_resume = platform_pm_runtime_resume,   .runtime_idle = platform_pm_runtime_idle,  };    struct bus_type platform_bus_type = {   .name  = "platform",   .dev_attrs = platform_dev_attrs,   .match  = platform_match,   .uevent  = platform_uevent,   .pm  = &platform_dev_pm_ops,  };

  从上面的dev_pm_ops结构体中拿出最普遍使用的函数指针来说明一下，对于bus_type它的电源管理是如何实现的。

  static int platform_pm_prepare(struct device *dev)  {   struct device_driver *drv = dev->driver;   int ret = 0;     if (drv && drv->pm && drv->pm->prepare)    ret = drv->pm->prepare(dev);     return ret;  }  static void platform_pm_complete(struct device *dev)  {   struct device_driver *drv = dev->driver;     if (drv && drv->pm && drv->pm->complete)    drv->pm->complete(dev);  }

  可以看出这两个函数都最终是利用了device_driver结构体中的dev_pm_ops函数方法结构体中的对应函数指针。
  再看platform_pm_suspend和platform_pm_resume。

  static int platform_legacy_suspend(struct device *dev, pm_message_t mesg)  {   struct platform_driver *pdrv = to_platform_driver(dev->driver);   struct platform_device *pdev = to_platform_device(dev);   int ret = 0;     if (dev->driver && pdrv->suspend)    ret = pdrv->suspend(pdev, mesg);     return ret;  }    static int platform_legacy_resume(struct device *dev)  {   struct platform_driver *pdrv = to_platform_driver(dev->driver);   struct platform_device *pdev = to_platform_device(dev);   int ret = 0;     if (dev->driver && pdrv->resume)    ret = pdrv->resume(pdev);     return ret;  }

  static int platform_pm_suspend(struct device *dev)  {   struct device_driver *drv = dev->driver;   int ret = 0;     if (!drv)    return 0;     if (drv->pm) {    if (drv->pm->suspend)     ret = drv->pm->suspend(dev);   } else {    ret = platform_legacy_suspend(dev, PMSG_SUSPEND);   }     return ret;  }    static int platform_pm_resume(struct device *dev)  {   struct device_driver *drv = dev->driver;   int ret = 0;     if (!drv)    return 0;     if (drv->pm) {    if (drv->pm->resume)     ret = drv->pm->resume(dev);   } else {    ret = platform_legacy_resume(dev);   }     return ret;  }

    这里suspend和resume函数也是最终都是调用了device_driver结构体的dev_pm_ops方法结构体中的对应函数指针(device_driver.pm项被初始化)，否则使用老式的方法：platform_legacy_suspend(dev, PMSG_SUSPEND)和platform_legacy_resume(dev)。根据这两个函数的源码可以看出。一般地，在我们的platform device的platform driver定义中，都是实现了pdrv.suspend和pdrv.resume函数，而并没有实现pdrv.driver.suspend和pdrv.driver.resume函数（是struct device_driver没有做默认实现，platform_driver也不没有使用platform_drv_suspend/platform_drv_resume之类去回调i2c_driver.suspend，而是由platform_pm_suspend去调用，纳入PM core管理），其余三个函数可以在platform_driver_register()函数中看出：

  int platform_driver_register(struct platform_driver *drv)  {   drv->driver.bus = &platform_bus_type;   if (drv->probe)    drv->driver.probe = platform_drv_probe;   if (drv->remove)    drv->driver.remove = platform_drv_remove;   if (drv->shutdown)    drv->driver.shutdown = platform_drv_shutdown;     return driver_register(&drv->driver);  }

  i2c总线注册没有使用新式的电源管理方法：dev_pm_ops，仍然使用老式的方式：

  @kernel/drivers/i2c/i2c-core.c  struct bus_type i2c_bus_type = {   .name  = "i2c",   .match  = i2c_device_match,   .probe  = i2c_device_probe,   .remove  = i2c_device_remove,   .shutdown = i2c_device_shutdown,   .suspend = i2c_device_suspend,   .resume  = i2c_device_resume,  };

 

  static int i2c_device_suspend(struct device *dev, pm_message_t mesg)  {   struct i2c_client *client = i2c_verify_client(dev);   struct i2c_driver *driver;     if (!client || !dev->driver)    return 0;   driver = to_i2c_driver(dev->driver);   if (!driver->suspend)    return 0;   return driver->suspend(client, mesg);  }    static int i2c_device_resume(struct device *dev)  {   struct i2c_client *client = i2c_verify_client(dev);   struct i2c_driver *driver;     if (!client || !dev->driver)    return 0;   driver = to_i2c_driver(dev->driver);   if (!driver->resume)    return 0;   return driver->resume(client);  }

  2. device_type结构体暂时还没有找到有哪一个模块使用了新式了dev_pm_ops电源管理方法，一般都是没有实现这部分。
  
  3. class结构体也没有找到使用dev_pm_ops方法结构体的地方，先暂时放一放。
  
  4. device_driver

    struct device_driver {    const char  *name;    struct bus_type  *bus;    ...    int (*probe) (struct device *dev);    int (*remove) (struct device *dev);    void (*shutdown) (struct device *dev);    int (*suspend) (struct device *dev, pm_message_t state);    int (*resume) (struct device *dev);    const struct attribute_group **groups;       const struct dev_pm_ops *pm;       struct driver_private *p;   };   

platform driver和i2c_driver结构体都是实现了suspend和resume函数，并没有使用新式的电源管理方式。

   struct i2c_driver {    ...    /* driver model interfaces that don't relate to enumeration  */    void (*shutdown)(struct i2c_client *);    int (*suspend)(struct i2c_client *, pm_message_t mesg);    int (*resume)(struct i2c_client *);    ...    struct device_driver driver;    const struct i2c_device_id *id_table;       /* Device detection callback for automatic device creation */    int (*detect)(struct i2c_client *, int kind, struct i2c_board_info *);    const struct i2c_client_address_data *address_data;    struct list_head clients;   };