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