linux pinmux 引脚多路复用驱动分析与使用
一、网上的文章一般都是分析pinctrl驱动的,从头到尾分析了一遍,搞的相当复杂,实际上没那么复杂二、pinmux的概要分析,有关文件如下/pinctrl/core.c、/pinctrl/Pinmux.c、平台相关的结构体pinctrl_state,pinctrl_setting,pinmux_ops,pinctrl_desc,pinctrl_map,基本原理如下:1、通过在平台相关的pin...
一、网上的文章一般都是分析pinctrl驱动的,从头到尾分析了一遍,搞的相当复杂,实际上没那么复杂
二、pinmux的概要分析,有关文件如下/pinctrl/core.c、/pinctrl/Pinmux.c、平台相关的结构体pinctrl_state,pinctrl_setting,pinmux_ops,pinctrl_desc,pinctrl_map,基本原理如下:
1、通过在平台相关的pinctrl驱动初始化函数pinctrl_probe,调用pinctrl_register函数,将平台相关的,已经定义好的函数指针等通过结构体封装,传给该函数,相当于已经注册好了;
2、不管是core.c里面的实现,还是Pinmux.c里面的实现,无非是最终会通过回调函数,调用到上面提到的平台相关的已经定义好的实现,包括以功能为依据的分组,比如SPI、UART的引脚的配置,完成引脚的功能配置
3、这就是linux下面抽象出了各种功能,形成了一个中间件,对上层app提供统一的接口,下层各个soc厂商按照定义好的格式对其进行实现,最后上层app就会调用到底层来
4、当然,pinmux的实现利用了很多机制,比如链表的插入、遍历等等
三、具体到代码,如何调用API实现引脚功能复用呢?
1、直接在代码中调用这个API即可,devm_pinctrl_get_select( struct device *dev, const char *name),参考其他地方的调用,可以直接针对功能进行引脚复用的配置,当然,前提是pinctrl-soc.c里面已经做好了相关配置,这里的soc指的是ARM平台,比如高通、三星、MTK、TI等等。
linux pinctrl 配置_这个ID洒家要了的博客-CSDN博客_pinctrl_lookup_state
Linux内核中的pinctrl子系统应用实例
主要函数
struct pinctrl *devm_pinctrl_get(struct device *dev)
pinctrl_lookup_state //寻找一个pin的配置
pinctrl_select_state // 设置选择一个pin的配置
由于近期在做一个项目用到了pinctrl子系统,但是对pinctrl子系统了解又不是很多,所以遇到了麻烦,但是找度娘发现很少有同行对pinctrl的具体用法做出说明,所以只能自己去搞了,在经过一段时间对Linux内核源码的折腾,最终搞定,并将我所应用的实例给展示一下,希望对大家有所帮助。
关于pinctrl是什么,为什么要用pinctrl,源码深度剖析我在这就不赘述了,有位博友总结的非常好,大家可以参考GPIO子GPIO子系统 - 蜗窝科技GPIO子。
下面我介绍一下如何去使用内核中的pinctrl子系统以device tree设备树为例,当你需要控制某些pin的时候,你首先要在devicetree中去按照pinctrl的规则去描述它,然后才能在driver中去使用:
案例1:
xxx这个设备要用到gpg0_1这个pin的TE_DECON_INT功能,并分别将这两个状态取了个名字turnon_tes和turnoff_tes.这个名字是随便起的。重点是看pinctrl-0和pinctrl-1,根据示例,它们分别引用了disp_teson和disp_tesoff这两个节点。
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>;
};
两个重要的属性必须有:pins 和 pin-function分别是pin的名字和要把pin配置成什么功能,还有gpg0属于pinctrl_2,所以这个地方引用的是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 -- 对应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
};
};
那么driver如何去操作这个pin呢?首先需要大家熟悉几个内核的API:
1. 获取一个pinctrl句柄,参数是dev是包含这个pin的device结构体即xxx这个设备的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. 获取这个pin对应pin_state(引脚状态-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. 设置引脚为为某个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)
具体操作:
/* 获取pin control state holder 的句柄 */
pinctrl = devm_pinctrl_get(dev);
/* 得到名字为turnon_tes和turnoff_tes对应的pin state */
struct pinctrl_state * turnon_tes = pinctrl_lookup_state(pinctrl, "turnon_tes");
struct pinctrl_state * turnoff_tes = pinctrl_lookup_state(pinctrl, "turnoff_tes");
/* 设置名字为turnon_tes这个pinctrl对应引脚(gpg0-1)的pin state,即gpg0_1对应的寄存器位域设置为2 */
pinctrl_select_state(pinctrl, turnon_tes)。
/* 获取pin control state holder 的句柄 */
pinctrl = devm_pinctrl_get(dev);
/* 得到名字为turnon_tes和turnoff_tes对应的pin state */
struct pinctrl_state * turnon_tes = pinctrl_lookup_state(pinctrl, "turnon_tes");
struct pinctrl_state * turnoff_tes = pinctrl_lookup_state(pinctrl, "turnoff_tes");
/* 设置名字为turnon_tes这个pinctrl对应引脚(gpg0-1)的pin state,即gpg0_1对应的寄存器位域设置为2 */
pinctrl_select_state(pinctrl, turnon_tes)。
经过以上操作,gpg_1引脚对应的con寄存器的对应的位域被配置成2,即0x2 = TE_DECON_INT功能。同意,根据此方法也可以设置turnoff_tes的状态。
案例2 -- 一个背光灯device需要使用pwm的输出pin:
device tree:
背光系统中要用到gpd2_4这个pin的TOUT_0功能和gpd4_3这个pin的输出功能并输出1,需要在backlight这个node中做以下描述,这两个pin只有一个状态(pwm-on),同样,这个名字也是可以随便起的。bl_pwm_ctrl和bl_pwm_en_ctrl分别是对这两个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;">这个和上面一样,就不多说了</span> */
/* 这个和上面一样,就不多说了 */
&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
};
};
这个描述比上面多了个pin-val,因为这个引脚不仅要配置成输出功能,还要输出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);
执行完以上操作,可以发现gpd2_4引脚被配置成了TOUT_0功能,gpd4_3引脚被配置成为了输出功能,并且输出1(高电平)。
以上就是pinctrl子系统的应用实例。如果有解释不太正确的地方请指教。
外部接口
1.pinctrl
pinctrl_get
pinctrl_put
devm_pinctrl_get
devm_pinctrl_put
pinctrl_lookup_state
pinctrl_select_state
devm_pinctrl_get_select
devm_pinctrl_get_select_default
pin_config_get
pin_config_set
pin_config_group_get
pin_config_group_set
2.gpio
gpio_request
gpio_free
gpio_direction_input
gpio_direction_output
__gpio_get_value
__gpio_set_value
of_get_named_gpio
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