新版linux系统设备架构中关于电源管理方式的变更

出处：http://blog.csdn.net/coolraining/article/details/6678759

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。

////////////////////////////////////////////

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，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);

}

// 实际上都是调用的i2c_driver结构体的suspend和resume函数。

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;

};

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;

};

一般都是实现了platform driver和i2c_driver结构体的suspend和resume函数,并没有使用新式的电源管理方式。