《嵌入式 Linux 系统的电源管理》讲义

} struct bus_type i2c_bus_type = {
.name = "i2c", .match = i2c_device_match, .suspend = i2c_bus_suspend, .resume = i2c_bus_resume,
}; static int i2c_bus_suspend(struct device* dev, u32 state){
all children devices must be powered down before
their parent can be powered down. Conversely, the parent device must be powered up before any children devices may be accessed. Only when a device's depend count (struct device_pm::depend field.)is 0 may it be powered down. int device_pm_get/put(struct device *);
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Kernel PM_Subsystem
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Kernel PM_Subsystem
What we will talk Covers the two
broad areas of power management:
System Power Management (SPM) Device Power Management (DPM) And more……
if (dev->driver && dev->driver->suspend) rc = dev->driver->suspend(dev,state,0);
} //Device Specified driver, explain later
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Register PM handlers
static struct device_driver
The Xscale PXA27X CPU supports
several power-saving features.
Hale Waihona Puke 远见品质Xscale CPU PM Features
PXA27X PM features, including frequency
scaling and CPU core voltage scaling. And several modes of operation:
}; static int __init i2c_adap_pxa_init(void){
return driver_register(&i2c_pxa_driver);
}
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Register PM handlers
static int
i2c_pxa_controller_suspend(struct device *dev, u32 state, u32 level){
one to save state another to power the device down
Conversely,
one call is made to the resume() method to power the device up another to restore device state.
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Device PM Data Structs
A device's PM infor stored in struct
device_pm, struct device contains a device_pm object. struct device_pm
{
dev_power_t u8 atomic_t atomic_t struct kobject }; power_state; * saved_state; depend; disable; kobj;
(n can be “0~3”)
When n == 0 (resume steps similar)
state_store() [drivers/base/power/sysfs.c] -> dpm_runtime_suspend() [drivers/base/power/runtime.c] -> suspend_device() [drivers/base/power/suspend.c] -> • call suspend handler of the bus which the specified device belongs to . -> • call suspend handler for the specified device
The success's road
CE Linux PM
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What We’ll Talk
PM Theory and Hardware Support 2.6 kernel PM_Subsystem
CELF PM Specification Appendix
Current PM Implementation
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System Power Management (SPM)
System PM
The entire system is placed into a low-power state. running system is saved before powered down, and restored once the system has regained power. Automatically enter a low-power state after it has been idle for some amount of time, or when some critical state has been reached. Also policy decisions that are up to the user to configure and require some global mechanism for controlling.
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Device PM Data Structs
typedef enum {
DEVICE_PM_ON, DEVICE_PM_INT1, DEVICE_PM_INT2, DEVICE_PM_OFF, DEVICE_PM_UNKNOWN, //Device’s initial power state
Run mode All power supplies enabled, all clocks running and every on-chip resource is functional. Idle mode CPU clock stopped. other on-chip resources are active. When an interrupt occurs, the CPU is reactivated. Sleep mode Power is switched off to the majority of the processor. Some preprogrammed event, such as a power button press, wakes up the CPU from this mode
#ifdef CONFIG_PM i2c_pxa_wait_bus_not_busy(); i2c_pxa_stop(); #endif return 0;
}
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Internal Sequence of Device PM
echo n > /sys/bus/i2c/devices/1-1/power/state
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Register PM handlers
static int __init i2c_init(void){ retval = bus_register(&i2c_bus_type); retval = driver_register(&i2c_adapter_driver); return class_register(&i2c_adapter_class);
} dev_power_t; enum {
SUSPEND_SAVE_STATE, SUSPEND_POWER_DOWN,
}; enum {
RESUME_POWER_ON, RESUME_RESTORE_STATE,
};
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Power Dependencies
Two steps to suspend device
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Handheld Energy Budgets
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PM Theory
OS PM focuses on active power
consumption Modulate methods：
Voltage/clock modulate Clock selected Power supply selected
i2c_adapter_driver = {
.name = "i2c_adapter", .bus = &i2c_bus_type, .probe = i2c_device_probe, .remove = i2c_device_remove,
}; static struct class i2c_adapter_class = {
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