分析用的内核版本为5.1.3

1.MFD全称

Multi-function Device,多功能设备

2. 为何会出现MFD子系统

由于出现了一类具有多种功能的外围设备或cpu内部集成的硬件模块

3. 有哪些多功能设备呢?

3.1 PMIC,电源管理芯片

da9063: 调节器,led控制器,看门狗,实时时钟控制器,温度传感器,震动马达驱动,长按关机功能(ON key)

max77843: 调节器,充电器,燃油量表,触觉反馈,led控制器,micro USB接口控制器

wm831x: 调节器,时钟,实时时钟控制器,看门狗,触摸控制器,温度传感器,背光控制器,状态led控制器,GPIO,长按关机功能(ON key),ADC

其它: 甚至具有codec功能

3.2 atmel-hlcdc: 显示控制器和背光pwm

3.3 Diolan DLN2: USB转I2C,SPI和GPIO控制器

3.4 Realtek PCI-E读卡器: SD/MMC和记忆棒读取器

4. MFD子系统解决的主要问题

在不同的内核子系统中注册这些驱动。特别是外部外围设备仅仅由一个结构体struct device(或是指定的i2c_client或spi_device)呈现

5. MFD子系统的优点有哪些?

5.1 允许在多个子系统中注册相同的设备

5.2 MFD驱动必须能否复用总线(主要是关于锁的处理)和处理中断请求

5.3 处理时钟

5.4 需要配置IP

5.5 允许驱动重用,多个多功能设备能重用其它子系统中的驱动

6. MFD提供的API

int mfd_add_devices(struct device *parent,int id,

const struct mfd_cell *cells, int n_devs,

struct resource *mem_base,

int irq_base, struct irq_domain *irq_domain);

extern void mfd_remove_devices(struct device *parent);

这些接口定义在include/linux/mfd/core.h中,在drivers/mfd/mtd-core.c中被实现

7. MFD提供的结构体

struct mfd_cell {

const char *name;

int id;

/* refcounting for multiple drivers to use a single cell */

atomic_t *usage_count;

int (*enable)(struct platform_device *dev);

int (*disable)(struct platform_device *dev);

int (*suspend)(struct platform_device *dev);

int (*resume)(struct platform_device *dev);

/* platform data passed to the sub devices drivers */

void *platform_data;

size_t pdata_size;

/* device properties passed to the sub devices drivers */

struct property_entry *properties;

/*

* Device Tree compatible string

* See: Documentation/devicetree/usage-model.txt Chapter 2.2 for details

*/

const char *of_compatible;

/* Matches ACPI */

const struct mfd_cell_acpi_match *acpi_match;

/*

* These resources can be specified relative to the parent device.

* For accessing hardware you should use resources from the platform dev

*/

int num_resources;

const struct resource *resources;

/* don't check for resource conflicts */

bool ignore_resource_conflicts;

/*

* Disable runtime PM callbacks for this subdevice - see

* pm_runtime_no_callbacks().

*/

bool pm_runtime_no_callbacks;

/* A list of regulator supplies that should be mapped to the MFD

* device rather than the child device when requested

*/

const char * const *parent_supplies;

int num_parent_supplies;

};

8. 示例分析

8.1 分析tps6507x的多功能驱动

8.1.1 涉及的文件

drivers/mfd/tps6507x.c

include/linux/mfd/tps6507x.h

drivers/regulator/tps6507x-regulator.c

drivers/input/touchscreen/tps6507x-ts.c

8.1.2 涉及的结构体

static const struct mfd_cell tps6507x_devs[] = {

{

.name = "tps6507x-pmic",

},

{

.name = "tps6507x-ts",

},

};

从以上结构体可以得出,tps6507x系列芯片提供两种功能: 电源管理功能(regulator)+触摸屏功能(touchscreen)

static struct i2c_driver tps6507x_i2c_driver = {

.driver = {

.name = "tps6507x",

.of_match_table = of_match_ptr(tps6507x_of_match),

},

.probe = tps6507x_i2c_probe,

.id_table = tps6507x_i2c_id,

};

这个结构体为tps6507x提供探测函数tps6507x_i2c_probe

struct tps6507x_dev {

struct device *dev;

struct i2c_client *i2c_client;

int (*read_dev)(struct tps6507x_dev *tps6507x, char reg, int size,

void *dest);

int (*write_dev)(struct tps6507x_dev *tps6507x, char reg, int size,

void *src);

/* Client devices */

struct tps6507x_pmic *pmic;

};

tps6507x 的读写接口就是放在这个结构体中,这也就是所谓的共性

8.1.3 对tps6507x进行初始化

subsys_initcall(tps6507x_i2c_init);

调用路径如下:

tps6507x_i2c_init->i2c_add_driver

8.1.4 探测函数tps6507x_i2c_probe做了些什么？

注册tps6507x的读写函数: tps6507x_i2c_read_device和tps6507x_i2c_write_device到结构体struct tps6507x_dev中

8.1.5 tps6507x的两种功能实现在哪里呢?

drivers/regulator/tps6507x-regulator.c,这里面实现电源管理功能(电压调节器驱动)

drivers/input/touchscreen/tps6507x-ts.c,这里面实现触摸屏功能

8.1.6 tps6507x电压调节器驱动

8.1.6.1 调用路径

subsys_initcall(tps6507x_pmic_init);

tps6507x_pmic_init->platform_driver_register

8.1.6.2 探测函数tps6507x_pmic_probe干了些什么?

获取共用的结构体struct tps6507x_dev

再注册相关的结构体以便提供pmic的相关操作接口,如下:

static struct regulator_ops tps6507x_pmic_ops = {

.is_enabled = tps6507x_pmic_is_enabled, 检查tps6507x的pmic功能是否已经使能了

.enable = tps6507x_pmic_enable, 使能tps6507x的pmic功能

.disable = tps6507x_pmic_disable, 禁用tsp6507x的pmic功能

.get_voltage_sel = tps6507x_pmic_get_voltage_sel, 获取电压值

.set_voltage_sel = tps6507x_pmic_set_voltage_sel, 设置电压值

.list_voltage = regulator_list_voltage_table, 列出电压表

.map_voltage = regulator_map_voltage_ascend,

};

8.1.7 tps6507x触摸屏驱动

8.1.7.1 驱动在哪里?

drivers/input/touchscreen/tps6507x-ts.c

8.1.7.2 分析probe函数都做了些什么?

获取公用的结构体struct tps6507x_dev

填充结构体struct tps6507x_ts，关键是注册了函数tps6507x_ts_poll

参考资料:

标签：MFD,struct,int,tps6507x,内核,linux,device,i2c,pmic

来源： https://www.cnblogs.com/dakewei/p/10991941.html