linux pinctrl 配置

Linux內核中的pinctrl子系統應用實例

主要函數

struct pinctrl *devm_pinctrl_get(struct device *dev)

pinctrl_lookup_state    //尋找一個pin的配置

pinctrl_select_state   // 設置選擇一個pin的配置

由於近期在做一個項目用到了pinctrl子系統，但是對pinctrl子系統瞭解又不是很多，所以遇到了麻煩，但是找度娘發現很少有同行對pinctrl的具體用法做出說明，所以只能自己去搞了，在經過一段時間對Linux內核源碼的折騰，最終搞定，並將我所應用的實例給展示一下，希望對大家有所幫助。

關於pinctrl是什麼，爲什麼要用pinctrl，源碼深度剖析我在這就不贅述了，有位博友總結的非常好，大家可以參考http://www.wowotech.net/sort/gpio_subsystem。

下面我介紹一下如何去使用內核中的pinctrl子系統以device tree設備樹爲例，當你需要控制某些pin的時候，你首先要在devicetree中去按照pinctrl的規則去描述它，然後才能在driver中去使用：

案例1：

xxx這個設備要用到gpg0_1這個pin的TE_DECON_INT功能，並分別將這兩個狀態取了個名字turnon_tes和turnoff_tes.這個名字是隨便起的。重點是看pinctrl-0和pinctrl-1，根據示例，它們分別引用了disp_teson和disp_tesoff這兩個節點。

xxx {
    ....
    pinctrl-names = "turnon_tes", "turnoff_tes";
    pinctrl-0 = <&disp_teson>;
    pinctrl-1 = <&disp_tesoff>;
};

xxx {
    ....
    pinctrl-names = "turnon_tes", "turnoff_tes";
    pinctrl-0 = <&disp_teson>;
    pinctrl-1 = <&disp_tesoff>;
};

兩個重要的屬性必須有：pins 和 pin-function分別是pin的名字和要把pin配置成什麼功能，還有gpg0屬於pinctrl_2,所以這個地方引用的是pinctrl_2而不是其他。

&disp_teson_pinctrl {                           //#define disp_teson_pinctrl    pinctrl_2
    disp_teson: disp_teson {
        samsung,pins = disp_teson_pin;          //#define disp_teson_pin    "gpg0-1"
        samsung,pin-function = <disp_teson_con>;//#define disp_teson_con    2 -- 對應0x2 = TEDECON_INT
    };
};
&disp_tesoff_pinctrl {
    disp_tesoff: disp_tesoff {
        samsung,pins = disp_tesoff_pin;          //#define disp_teson_pin        "gpg0-1"
        samsung,pin-function = <disp_tesoff_con>;//#define disp_teson_con         0
    };
};

&disp_teson_pinctrl {                           //#define disp_teson_pinctrl	pinctrl_2
    disp_teson: disp_teson {
        samsung,pins = disp_teson_pin;          //#define disp_teson_pin    "gpg0-1"
        samsung,pin-function = <disp_teson_con>;//#define disp_teson_con    2 -- 對應0x2 = TEDECON_INT
    };
};
&disp_tesoff_pinctrl {
    disp_tesoff: disp_tesoff {
        samsung,pins = disp_tesoff_pin;          //#define disp_teson_pin        "gpg0-1"
        samsung,pin-function = <disp_tesoff_con>;//#define disp_teson_con         0
    };
};

那麼driver如何去操作這個pin呢？首先需要大家熟悉幾個內核的API：

1. 獲取一個pinctrl句柄，參數是dev是包含這個pin的device結構體即xxx這個設備的device

/**
 * struct devm_pinctrl_get() - Resource managed pinctrl_get()
 * @dev: the device to obtain the handle for
 *
 * If there is a need to explicitly destroy the returned struct pinctrl,
 * devm_pinctrl_put() should be used, rather than plain pinctrl_put().
 */
struct pinctrl *devm_pinctrl_get(struct device *dev)

/**
 * struct devm_pinctrl_get() - Resource managed pinctrl_get()
 * @dev: the device to obtain the handle for
 *
 * If there is a need to explicitly destroy the returned struct pinctrl,
 * devm_pinctrl_put() should be used, rather than plain pinctrl_put().
 */
struct pinctrl *devm_pinctrl_get(struct device *dev)

2. 獲取這個pin對應pin_state（引腳狀態-turnon_tes/turnoff_tes）

/**
 * pinctrl_lookup_state() - retrieves a state handle from a pinctrl handle
 * @p: the pinctrl handle to retrieve the state from
 * @name: the state name to retrieve
 */
struct pinctrl_state *pinctrl_lookup_state(struct pinctrl *p, const char *name)

/**
 * pinctrl_lookup_state() - retrieves a state handle from a pinctrl handle
 * @p: the pinctrl handle to retrieve the state from
 * @name: the state name to retrieve
 */
struct pinctrl_state *pinctrl_lookup_state(struct pinctrl *p, const char *name)

3. 設置引腳爲爲某個stata -- turnon_tes/turnoff_tes

/**
 * pinctrl_select_state() - select/activate/program a pinctrl state to HW
 * @p: the pinctrl handle for the device that requests configuration
 * @state: the state handle to select/activate/program
 */
int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)

/**
 * pinctrl_select_state() - select/activate/program a pinctrl state to HW
 * @p: the pinctrl handle for the device that requests configuration
 * @state: the state handle to select/activate/program
 */
int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)

具體操作：

/* 獲取pin control state holder 的句柄 */
pinctrl = devm_pinctrl_get(dev);
/* 得到名字爲turnon_tes和turnoff_tes對應的pin state */
struct pinctrl_state * turnon_tes = pinctrl_lookup_state(pinctrl, "turnon_tes");
struct pinctrl_state * turnoff_tes = pinctrl_lookup_state(pinctrl, "turnoff_tes");
/* 設置名字爲turnon_tes這個pinctrl對應引腳（gpg0-1）的pin state，即gpg0_1對應的寄存器位域設置爲2 */
pinctrl_select_state(pinctrl, turnon_tes)。

/* 獲取pin control state holder 的句柄 */
pinctrl = devm_pinctrl_get(dev);                                     
/* 得到名字爲turnon_tes和turnoff_tes對應的pin state */
struct pinctrl_state * turnon_tes = pinctrl_lookup_state(pinctrl, "turnon_tes");     
struct pinctrl_state * turnoff_tes = pinctrl_lookup_state(pinctrl, "turnoff_tes");
/* 設置名字爲turnon_tes這個pinctrl對應引腳（gpg0-1）的pin state，即gpg0_1對應的寄存器位域設置爲2 */
pinctrl_select_state(pinctrl, turnon_tes)。

經過以上操作，gpg_1引腳對應的con寄存器的對應的位域被配置成2，即0x2 = TE_DECON_INT功能。同意，根據此方法也可以設置turnoff_tes的狀態。

案例2 -- 一個背光燈device需要使用pwm的輸出pin：
device tree：
背光系統中要用到gpd2_4這個pin的TOUT_0功能和gpd4_3這個pin的輸出功能並輸出1，需要在backlight這個node中做以下描述，這兩個pin只有一個狀態（pwm-on），同樣，這個名字也是可以隨便起的。bl_pwm_ctrl和bl_pwm_en_ctrl分別是對這兩個pin的描述。

backlight {
    ...
    ...
    pinctrl-names = "pwm-on";
    pinctrl-0 = <&bl_pwm_ctrl @bl_pwm_en_ctrl>;
}；

backlight {
    ...
    ...
    pinctrl-names = "pwm-on";
    pinctrl-0 = <&bl_pwm_ctrl @bl_pwm_en_ctrl>;
}；

/* <span style="color: rgb(51, 51, 51); font-family: KaiTi_GB2312; font-size: 18px; line-height: 24.5px;">這個和上面一樣，就不多說了</span> */

/* 這個和上面一樣，就不多說了 */

&bl_pwm_ctrl_pinctrl{                                     //#define bl_pwm_ctrl_pinctrl   pinctrl_2
    bl_pwm_ctrl: bl_pwm_ctrl {
        samsung,pins = bl_pwm_ctrl_pin;           //#define bl_pwm_ctrl_pin   "gpd2-4"
        samsung,pin-function = <bl_pwm_ctrl_con>; //#define bl_pwm_ctrl_con       2
        samsung,pin-pud = <bl_pwm_ctrl_pull>;     //#define bl_pwm_ctrl_pull      3
        samsung,pin-drv = <bl_pwm_ctrl_drv>;      //#define bl_pwm_ctrl_drv       0
    };
};

&bl_pwm_ctrl_pinctrl{                                     //#define bl_pwm_ctrl_pinctrl   pinctrl_2   
	bl_pwm_ctrl: bl_pwm_ctrl {
		samsung,pins = bl_pwm_ctrl_pin;           //#define bl_pwm_ctrl_pin	  "gpd2-4"
		samsung,pin-function = <bl_pwm_ctrl_con>; //#define bl_pwm_ctrl_con		2
		samsung,pin-pud = <bl_pwm_ctrl_pull>;     //#define bl_pwm_ctrl_pull		3
		samsung,pin-drv = <bl_pwm_ctrl_drv>;      //#define bl_pwm_ctrl_drv		0
	};
};

這個描述比上面多了個pin-val，因爲這個引腳不僅要配置成輸出功能，還要輸出1，所以pin-val = 1。

&bl_pwm_en_ctrl_pinctrl{
    bl_pwm_en_ctrl: bl_pwm_en_ctrl {
        samsung,pins = bl_pwm_en_ctrl_pin;           //#define bl_pwm_en_ctrl_pin     "gpd4-3"
        samsung,pin-function = <bl_pwm_en_ctrl_con>; //#define bl_pwm_en_ctrl_con      1
        samsung,pin-val = <1>;
        samsung,pin-pud = <bl_pwm_en_ctrl_pull>;
        samsung,pin-drv = <bl_pwm_en_ctrl_drv>;
    };
};

&bl_pwm_en_ctrl_pinctrl{
	bl_pwm_en_ctrl: bl_pwm_en_ctrl {
		samsung,pins = bl_pwm_en_ctrl_pin;           //#define bl_pwm_en_ctrl_pin     "gpd4-3"
		samsung,pin-function = <bl_pwm_en_ctrl_con>; //#define bl_pwm_en_ctrl_con      1
		samsung,pin-val = <1>;
		samsung,pin-pud = <bl_pwm_en_ctrl_pull>;
		samsung,pin-drv = <bl_pwm_en_ctrl_drv>;
	};
};

driver的操作：

在backlight的driver的probe中：

struct pinctrl * p = devm_pinctrl_get(&pdev->dev);
struct pinctrl_state * default_state = pinctrl_lookup_state(p, "pwm-on");
pinctrl_select_state(p, default_state);

struct pinctrl * p = devm_pinctrl_get(&pdev->dev);
struct pinctrl_state * default_state = pinctrl_lookup_state(p, "pwm-on");
pinctrl_select_state(p, default_state);

執行完以上操作，可以發現gpd2_4引腳被配置成了TOUT_0功能，gpd4_3引腳被配置成爲了輸出功能，並且輸出1（高電平）。
以上就是pinctrl子系統的應用實例。如果有解釋不太正確的地方請指教。