详解linux电源管理驱动编写

对于嵌入式设备来说，合适的电源管理，不仅可以延长电池的寿命，而且可以省电，延长设备运行时间，在提高用户体验方面有很大的好处。所以，各个soc厂家在这方面花了很多的功夫。下面，我们可以看看linux是如何处理电源管理驱动的。

1、代码目录

drivers/regulator

2、查看目录下的Kconfig文件

menuconfig REGULATOR 
  bool "Voltage and Current Regulator Support" 
  help 
   Generic Voltage and Current Regulator support. 
 
   This framework is designed to provide a generic interface to voltage 
   and current regulators within the Linux kernel. It's intended to 
   provide voltage and current control to client or consumer drivers and 
   also provide status information to user space applications through a 
   sysfs interface. 
 
   The intention is to allow systems to dynamically control regulator 
   output in order to save power and prolong battery life. This applies 
   to both voltage regulators (where voltage output is controllable) and 
   current sinks (where current output is controllable). 
 
   This framework safely compiles out if not selected so that client 
   drivers can still be used in systems with no software controllable 
   regulators. 
 
   If unsure, say no.

3、阅读文件，得知REGULATOR是最核心的模块macro，那我们可以找一个设备的macro看看 

config REGULATOR_STM32_VREFBUF 
  tristate "STMicroelectronics STM32 VREFBUF" 
  depends on ARCH_STM32 || COMPILE_TEST 
  help 
   This driver supports STMicroelectronics STM32 VREFBUF (voltage 
   reference buffer) which can be used as voltage reference for 
   internal ADCs, DACs and also for external components through 
   dedicated Vref+ pin. 
 
   This driver can also be built as a module. If so, the module 
   will be called stm32-vrefbuf.

4、没有找到s3c，可以看一下stm32芯片的依赖属性，接着看Makefile

obj-$(CONFIG_REGULATOR) += core.o dummy.o fixed-helper.o helpers.o devres.o 
obj-$(CONFIG_OF) += of_regulator.o 
obj-$(CONFIG_REGULATOR_FIXED_VOLTAGE) += fixed.o 
obj-$(CONFIG_REGULATOR_VIRTUAL_CONSUMER) += virtual.o 
obj-$(CONFIG_REGULATOR_USERSPACE_CONSUMER) += userspace-consumer.o 
 
obj-$(CONFIG_REGULATOR_STM32_VREFBUF) += stm32-vrefbuf.o

5、看的出来stm32只依赖于stm32-verfbuf.c文件，继续查看

static const struct of_device_id stm32_vrefbuf_of_match[] = { 
  { .compatible = "st,stm32-vrefbuf", }, 
  {}, 
}; 
MODULE_DEVICE_TABLE(of, stm32_vrefbuf_of_match); 
 
static struct platform_driver stm32_vrefbuf_driver = { 
  .probe = stm32_vrefbuf_probe, 
  .remove = stm32_vrefbuf_remove, 
  .driver = { 
    .name = "stm32-vrefbuf", 
    .of_match_table = of_match_ptr(stm32_vrefbuf_of_match), 
  }, 
}; 
module_platform_driver(stm32_vrefbuf_driver);

6、确认驱动为platform驱动，寻找regulator特有的数据结构

static const struct regulator_ops stm32_vrefbuf_volt_ops = { 
  .enable   = stm32_vrefbuf_enable, 
  .disable  = stm32_vrefbuf_disable, 
  .is_enabled = stm32_vrefbuf_is_enabled, 
  .get_voltage_sel = stm32_vrefbuf_get_voltage_sel, 
  .set_voltage_sel = stm32_vrefbuf_set_voltage_sel, 
  .list_voltage  = regulator_list_voltage_table, 
}; 
 
static const struct regulator_desc stm32_vrefbuf_regu = { 
  .name = "vref", 
  .supply_name = "vdda", 
  .volt_table = stm32_vrefbuf_voltages, 
  .n_voltages = ARRAY_SIZE(stm32_vrefbuf_voltages), 
  .ops = &stm32_vrefbuf_volt_ops, 
  .type = REGULATOR_VOLTAGE, 
  .owner = THIS_MODULE, 
};

7、由代码得知，regulator_ops和regulator_desc才是特有的regulator数据结构，当然也少不了注册函数

rdev = regulator_register(&stm32_vrefbuf_regu, &config); 
if (IS_ERR(rdev)) { 
  ret = PTR_ERR(rdev); 
  dev_err(&pdev->dev, "register failed with error %d\n", ret); 
  goto err_clk_dis; 
} 
platform_set_drvdata(pdev, rdev);

8、进一步确认of_device_id是不是真实存在，可以在arch/arm/boot/dts/stm32h743.dtsi找到对应内容

vrefbuf: regulator@58003C00 { 
  compatible = "st,stm32-vrefbuf"; 
  reg = <0x58003C00 0x8>; 
  clocks = <&rcc VREF_CK>; 
  regulator-min-microvolt = <1500000>; 
  regulator-max-microvolt = <2500000>; 
  status = "disabled"; 
};