轉自：https://www.cnblogs.com/dakewei/p/10991941.html
分析用的內核版本為5.1.3
1.MFD全稱
Multi-function Device,多功能設備
2. 為何會出現MFD子系統
由於出現了一類具有多種功能的外圍設備或cpu內部集成的硬件模塊
3. 有哪些多功能設備呢?
3.1 PMIC,電源管理芯片
da9063: 調節器,led控制器,看門狗,實時時鍾控制器,溫度傳感器,震動馬達驅動,長按關機功能(ON key)
max77843: 調節器,充電器,燃油量表,觸覺反饋,led控制器,micro USB接口控制器
wm831x: 調節器,時鍾,實時時鍾控制器,看門狗,觸摸控制器,溫度傳感器,背光控制器,狀態led控制器,GPIO,長按關機功能(ON key),ADC
其它: 甚至具有codec功能
3.2 atmel-hlcdc: 顯示控制器和背光pwm
3.3 Diolan DLN2: USB轉I2C,SPI和GPIO控制器
3.4 Realtek PCI-E讀卡器: SD/MMC和記憶棒讀取器
4. MFD子系統解決的主要問題
在不同的內核子系統中注冊這些驅動。特別是外部外圍設備僅僅由一個結構體struct device(或是指定的i2c_client或spi_device)呈現
5. MFD子系統的優點有哪些?
5.1 允許在多個子系統中注冊相同的設備
5.2 MFD驅動必須能否復用總線(主要是關於鎖的處理)和處理中斷請求
5.3 處理時鍾
5.4 需要配置IP
5.5 允許驅動重用,多個多功能設備能重用其它子系統中的驅動
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);
這些接口定義在include/linux/mfd/core.h中,在drivers/mfd/mtd-core.c中被實現
7. MFD提供的結構體
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的多功能驅動
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 涉及的結構體
static const struct mfd_cell tps6507x_devs[] = {
{
.name = "tps6507x-pmic",
},
{
.name = "tps6507x-ts",
},
};
從以上結構體可以得出,tps6507x系列芯片提供兩種功能: 電源管理功能(regulator)+觸摸屏功能(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,
};
這個結構體為tps6507x提供探測函數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 的讀寫接口就是放在這個結構體中,這也就是所謂的共性
8.1.3 對tps6507x進行初始化
subsys_initcall(tps6507x_i2c_init);
調用路徑如下:
tps6507x_i2c_init->i2c_add_driver
8.1.4 探測函數tps6507x_i2c_probe做了些什么？
注冊tps6507x的讀寫函數: tps6507x_i2c_read_device和tps6507x_i2c_write_device到結構體struct tps6507x_dev中
8.1.5 tps6507x的兩種功能實現在哪里呢?
drivers/regulator/tps6507x-regulator.c,這里面實現電源管理功能（電壓調節器驅動）
drivers/input/touchscreen/tps6507x-ts.c,這里面實現觸摸屏功能
8.1.6 tps6507x電壓調節器驅動
8.1.6.1 調用路徑
subsys_initcall(tps6507x_pmic_init);
tps6507x_pmic_init->platform_driver_register
8.1.6.2 探測函數tps6507x_pmic_probe干了些什么?
獲取共用的結構體struct tps6507x_dev
再注冊相關的結構體以便提供pmic的相關操作接口,如下:
static struct regulator_ops tps6507x_pmic_ops = {
.is_enabled = tps6507x_pmic_is_enabled, 檢查tps6507x的pmic功能是否已經使能了
.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, 獲取電壓值
.set_voltage_sel = tps6507x_pmic_set_voltage_sel, 設置電壓值
.list_voltage = regulator_list_voltage_table, 列出電壓表
.map_voltage = regulator_map_voltage_ascend,
};
8.1.7 tps6507x觸摸屏驅動
8.1.7.1 驅動在哪里?
drivers/input/touchscreen/tps6507x-ts.c
8.1.7.2 分析probe函數都做了些什么?
獲取公用的結構體struct tps6507x_dev
填充結構體struct tps6507x_ts，關鍵是注冊了函數tps6507x_ts_poll
8.2 分析da9063相關驅動
8.2.1 mfd驅動
8.2.1.1 相關源碼
drivers/mfd/da9063-i2c.c
8.2.1.2 分析探測函數da9063_i2c_probe的調用路徑
da9063_i2c_probe->da9063_device_init
8.2.1.3 da9063_device_init做了些什么?
讀取da9063的芯片ID，檢查是否匹配
讀取da9063的variant ID,不同的variant ID表示不同的封裝
通過接口devm_mfd_add_devices添加具體的結構體struct mfd_cell數組,這個數組里包含了多個驅動相關的信息,如名字，資源等
8.2.1.4 結構體數組da906_common_devs
static const struct mfd_cell da9063_common_devs[] = {
{
.name = DA9063_DRVNAME_REGULATORS,
.num_resources = ARRAY_SIZE(da9063_regulators_resources),
.resources = da9063_regulators_resources,
},
{
.name = DA9063_DRVNAME_LEDS,
},
{
.name = DA9063_DRVNAME_WATCHDOG,
.of_compatible = "dlg,da9063-watchdog",
},
{
.name = DA9063_DRVNAME_HWMON,
.num_resources = ARRAY_SIZE(da9063_hwmon_resources),
.resources = da9063_hwmon_resources,
},
{
.name = DA9063_DRVNAME_ONKEY,
.num_resources = ARRAY_SIZE(da9063_onkey_resources),
.resources = da9063_onkey_resources,
.of_compatible = "dlg,da9063-onkey",
},
{
.name = DA9063_DRVNAME_VIBRATION,
},
};
這個結構體數組中就包含了調節器，led控制器，看門狗，硬件監測（電壓監測，溫度監測），長按關鍵功能（onkey），震動等驅動名稱，也就是da9063會關聯（具有）這些功能,da9063有兩種硬件版本，一種為DA9063,另一種為DA9063L,這兩種硬件的差異在於DA9063具有實時時鍾功能，而后者沒有此功能
8.2.1.5 結構體數組da9063_devs
/* Only present on DA9063 , not on DA9063L */
static const struct mfd_cell da9063_devs[] = {
{
.name = DA9063_DRVNAME_RTC,
.num_resources = ARRAY_SIZE(da9063_rtc_resources),
.resources = da9063_rtc_resources,
.of_compatible = "dlg,da9063-rtc",
},
};
8.2.1.6 da9063_common_devs和da9063_devs中的這些具體的驅動實現在哪里?
drivers/regulator/da9063-regulator.c (調節器驅動)
(沒有找到da9063的led控制器驅動)
drivers/watchdog/da9063_wdt.c (看門狗驅動)
(沒有找到da9063的硬件監測驅動)
drivers/input/misc/da9063_onkey.c （onkey驅動）
(沒有找到da9063的震動功能驅動)
drivers/rtc/rtc-da9063.c (實時時鍾驅動)
8.2.1.7 重要的結構體struct da9063
struct da9063 {
/* Device */
struct device *dev;
enum da9063_type type;
unsigned char variant_code;
unsigned int flags;
/* Control interface */
struct regmap *regmap;
/* Interrupts */
int chip_irq;
unsigned int irq_base;
struct regmap_irq_chip_data *regmap_irq;
};
參考資料: