Linux GPIO操作分析 - Exynos 5260

送给从STM32库或者其他单片机爬过来的熊孩纸

操作GPIO还是这个顺序：
1:开时钟（linux不用管）
2:设置属性
3:设置方向
4:看是否需要设置上下拉

我这个版本是exynos5260平台的，常规IO操作方式如下

通常在配置一个GPIO口时，首先通过gpio_request函数申请GPIO口，再通过s3c_gpio_cfgpin、s3c_gpio_setpull、gpio_set_value函数配置GPIO口，在不用时通过gpio_free函数释放GPIO口。

相关源码路径：
/*
kernel/drivers/gpio/gpiolib.c
kernel/arm/alpha/include/asm/gpio.h(和gpiolib的内容直接关联，由于三星源码版本，所以路径可能有差异)
kernel/drivers/gpio/gpio-samsung.c（所有API的source都在这里）
kernel/arch/arm/mach-exynos/include/mach/gpio.h
kernel/arch/arm/plat-samsung/include/plat/gpio-cfg.h
(老版本是linux/arch/arm/plat-s3c/include/plat/gpio-cfg.h，所有要用的API都集中在这个文件，还带参数宏，有故事的同学直接戳这个文件即可)
*/

内核中已经将GPIO的相关操作做好了，我们只需要调用即可。这里只给出几种常用的操作函数的使用方法，具体实现过程可以琢磨源码（kernel/drivers/gpio/gpio-samsung.c）。

一：设置GPIO上下拉属性的函数

// kernel/drivers/gpio/gpio-samsung.c 
int s3c_gpio_setpull(unsigned int pin, samsung_gpio_pull_t pull)
{
    struct samsung_gpio_chip *chip = samsung_gpiolib_getchip(pin);
    int offset, ret;

    if (!chip)
        return -EINVAL;

    offset = pin - chip->chip.base;
    ret = samsung_gpio_do_setpull(chip, offset, pull);

    return ret;
}
EXPORT_SYMBOL(s3c_gpio_setpull);

第一个传入参数表示需要设置的管脚编号，第二个传入参数表示上下拉的属性。每一个GPIO的管脚编号都可以通过宏来指定，这些宏都在kernel/arch/arm/mach-exynos/include/mach/gpio.h中定义。按照5260datasheet的寄存器介绍，GPIO可以配置成none，上拉或下拉三种状态，对应宏定义如下：

//kernel/arch/arm/plat-samsung/include/plat/gpio-cfg.h
/* Define values for the pull-{up,down} available for each gpio pin.
 *
 * These values control the state of the weak pull-{up,down} resistors
 * available on most pins on the S3C series. Not all chips support both
 * up or down settings, and it may be dependent on the chip that is being
 * used to whether the particular mode is available.
 */
#define S3C_GPIO_PULL_NONE  ((__force samsung_gpio_pull_t)0x00)
#define S3C_GPIO_PULL_DOWN  ((__force samsung_gpio_pull_t)0x01)
#define S3C_GPIO_PULL_UP    ((__force samsung_gpio_pull_t)0x03)

比如设置GPX0-1为上拉：

s3c_gpio_setpull(EXYNOS5260_GPX0(1), S3C_GPIO_PULL_UP);

二：设置GPIO功能属性的函数

// kernel/drivers/gpio/gpio-samsung.c 
int s3c_gpio_cfgpin(unsigned int pin, unsigned int config)
{
    struct samsung_gpio_chip *chip = samsung_gpiolib_getchip(pin);
    int offset;
    int ret;

    if (!chip)
        return -EINVAL;

    offset = pin - chip->chip.base;
    ret = samsung_gpio_do_setcfg(chip, offset, config);

    return ret;
}
EXPORT_SYMBOL(s3c_gpio_cfgpin);

第一个传入参数表示管脚编号，第二个传入参数表示配置信息，如下宏可以表述管脚的配置状态：

#define S3C_GPIO_SPECIAL_MARK   (0xfffffff0)
#define S3C_GPIO_SPECIAL(x) (S3C_GPIO_SPECIAL_MARK | (x))

/* Defines for generic pin configurations */
#define S3C_GPIO_INPUT  (S3C_GPIO_SPECIAL(0))
#define S3C_GPIO_OUTPUT (S3C_GPIO_SPECIAL(1))
#define S3C_GPIO_SFN(x) (S3C_GPIO_SPECIAL(x))

#define samsung_gpio_is_cfg_special(_cfg) \
    (((_cfg) & S3C_GPIO_SPECIAL_MARK) == S3C_GPIO_SPECIAL_MARK)

S3C_GPIO_SFN(0)或S3C_GPIO_INPUT表示将管脚设置为输入，S3C_GPIO_SFN(1)或S3C_GPIO_OUTPUT表示将管脚设置为输出，将管脚设置为其他复合的功能时，需参考5260芯片用户手册的寄存器参数表，结合S3C_GPIO_SFN宏使用。
以下程序表示将GPX0(1)管脚设置为输出：

s3c_gpio_cfgpin(EXYNOS5260_GPX0(1), S3C_GPIO_SFN(1));

当GPIO被设置为输出时，设置其电平状态属性的函数清单如下：

//kernel/arm/alpha/include/asm/gpio.h
static inline void gpio_set_value(unsigned int gpio, int value)
{
    __gpio_set_value(gpio, value);
}
//static inline int gpio_to_irq(unsigned int gpio)也在这个文件中

//kernel/drivers/gpio/gpiolib.c
/**
 * __gpio_set_value() - assign a gpio‘s value
 * @gpio: gpio whose value will be assigned
 * @value: value to assign
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_set_value().
 * It invokes the associated gpio_chip.set() method.
 */
void __gpio_set_value(unsigned gpio, int value)
{
    struct gpio_chip    *chip;

    chip = gpio_to_chip(gpio);
    /* Should be using gpio_set_value_cansleep() */
    WARN_ON(chip->can_sleep);
    trace_gpio_value(gpio, 0, value);
    if (test_bit(FLAG_OPEN_DRAIN,  &gpio_desc[gpio].flags))
        _gpio_set_open_drain_value(gpio, chip, value);
    else if (test_bit(FLAG_OPEN_SOURCE,  &gpio_desc[gpio].flags))
        _gpio_set_open_source_value(gpio, chip, value);
    else
        chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(__gpio_set_value);

gpio表示管脚编号，value表示电平状态，0表示低电平，1表示高电平。如下程序表示将GPD0(1)管脚设置为低电平：

gpio_set_value(EXYNOS5260_GPX0(1), 0);

gpio_request和gpio_free函数分别用于申请GPIO和释放GPIO，强烈建议在使用GPIO时，首先申请GPIO，用完后释放，避免IO口冲突。申请GPD0(1)作为GPIO口的程序清单如下：

gpio_request(EXYNOS5260_GPX0(1), "GPX0(1)");

这里第一个传入参数为IO口的管脚编号，第二个为IO口的名称，可自定义。释放GPX0(1)的程序清单如下：

gpio_free(EXYNOS5260_GPX0(1));

通常在配置一个GPIO口时，首先通过gpio_request函数申请GPIO口，再通过s3c_gpio_cfgpin、s3c_gpio_setpull、gpio_set_value函数配置GPIO口，在不用时通过gpio_free函数释放GPIO口。

最后直接贴完整的三星源码方便参考：

/* linux/arch/arm/plat-s3c/include/plat/gpio-cfg.h
 *
 * Copyright 2008 Openmoko, Inc.
 * Copyright 2008 Simtec Electronics
 *  http://armlinux.simtec.co.uk/
 *  Ben Dooks <ben@simtec.co.uk>
 *
 * S3C Platform - GPIO pin configuration
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
*/

/* This file contains the necessary definitions to get the basic gpio
 * pin configuration done such as setting a pin to input or output or
 * changing the pull-{up,down} configurations.
 */

/* Note, this interface is being added to the s3c64xx arch first and will
 * be added to the s3c24xx systems later.
 */

#ifndef __PLAT_GPIO_CFG_H
#define __PLAT_GPIO_CFG_H __FILE__

#include<linux/types.h>

typedef unsigned int __bitwise__ samsung_gpio_pull_t;
typedef unsigned int __bitwise__ s5p_gpio_drvstr_t;
typedef unsigned int __bitwise__ s5p_gpio_pd_cfg_t;
typedef unsigned int __bitwise__ s5p_gpio_data_t;
typedef unsigned int __bitwise__ s5p_gpio_pd_pull_t;

/* forward declaration if gpio-core.h hasn‘t been included */
struct samsung_gpio_chip;

/**
 * struct samsung_gpio_cfg GPIO configuration
 * @cfg_eint: Configuration setting when used for external interrupt source
 * @get_pull: Read the current pull configuration for the GPIO
 * @set_pull: Set the current pull configuraiton for the GPIO
 * @set_config: Set the current configuration for the GPIO
 * @get_config: Read the current configuration for the GPIO
 *
 * Each chip can have more than one type of GPIO bank available and some
 * have different capabilites even when they have the same control register
 * layouts. Provide an point to vector control routine and provide any
 * per-bank configuration information that other systems such as the
 * external interrupt code will need.
 *
 * @sa samsung_gpio_cfgpin
 * @sa s3c_gpio_getcfg
 * @sa s3c_gpio_setpull
 * @sa s3c_gpio_getpull
 */
struct samsung_gpio_cfg {
    unsigned int    cfg_eint;

    samsung_gpio_pull_t (*get_pull)(struct samsung_gpio_chip *chip, unsigned offs);
    int     (*set_pull)(struct samsung_gpio_chip *chip, unsigned offs,
                    samsung_gpio_pull_t pull);

    unsigned (*get_config)(struct samsung_gpio_chip *chip, unsigned offs);
    int  (*set_config)(struct samsung_gpio_chip *chip, unsigned offs,
                   unsigned config);
};

#define S3C_GPIO_SPECIAL_MARK   (0xfffffff0)
#define S3C_GPIO_SPECIAL(x) (S3C_GPIO_SPECIAL_MARK | (x))

/* Defines for generic pin configurations */
#define S3C_GPIO_INPUT  (S3C_GPIO_SPECIAL(0))
#define S3C_GPIO_OUTPUT (S3C_GPIO_SPECIAL(1))
#define S3C_GPIO_SFN(x) (S3C_GPIO_SPECIAL(x))

#define samsung_gpio_is_cfg_special(_cfg)     (((_cfg) & S3C_GPIO_SPECIAL_MARK) == S3C_GPIO_SPECIAL_MARK)

/**
 * s3c_gpio_cfgpin() - Change the GPIO function of a pin.
 * @pin pin The pin number to configure.
 * @to to The configuration for the pin‘s function.
 *
 * Configure which function is actually connected to the external
 * pin, such as an gpio input, output or some form of special function
 * connected to an internal peripheral block.
 *
 * The @to parameter can be one of the generic S3C_GPIO_INPUT, S3C_GPIO_OUTPUT
 * or S3C_GPIO_SFN() to indicate one of the possible values that the helper
 * will then generate the correct bit mask and shift for the configuration.
 *
 * If a bank of GPIOs all needs to be set to special-function 2, then
 * the following code will work:
 *
 *  for (gpio = start; gpio < end; gpio++)
 *      s3c_gpio_cfgpin(gpio, S3C_GPIO_SFN(2));
 *
 * The @to parameter can also be a specific value already shifted to the
 * correct position in the control register, although these are discouraged
 * in newer kernels and are only being kept for compatibility.
 */
extern int s3c_gpio_cfgpin(unsigned int pin, unsigned int to);

/**
 * s3c_gpio_getcfg - Read the current function for a GPIO pin
 * @pin: The pin to read the configuration value for.
 *
 * Read the configuration state of the given @pin, returning a value that
 * could be passed back to s3c_gpio_cfgpin().
 *
 * @sa s3c_gpio_cfgpin
 */
extern unsigned s3c_gpio_getcfg(unsigned int pin);

/**
 * s3c_gpio_cfgpin_range() - Change the GPIO function for configuring pin range
 * @start: The pin number to start at
 * @nr: The number of pins to configure from @start.
 * @cfg: The configuration for the pin‘s function
 *
 * Call s3c_gpio_cfgpin() for the @nr pins starting at @start.
 *
 * @sa s3c_gpio_cfgpin.
 */
extern int s3c_gpio_cfgpin_range(unsigned int start, unsigned int nr,
                 unsigned int cfg);

/* Define values for the pull-{up,down} available for each gpio pin.
 *
 * These values control the state of the weak pull-{up,down} resistors
 * available on most pins on the S3C series. Not all chips support both
 * up or down settings, and it may be dependent on the chip that is being
 * used to whether the particular mode is available.
 */
#define S3C_GPIO_PULL_NONE  ((__force samsung_gpio_pull_t)0x00)
#define S3C_GPIO_PULL_DOWN  ((__force samsung_gpio_pull_t)0x01)
#define S3C_GPIO_PULL_UP    ((__force samsung_gpio_pull_t)0x03)

/**
 * s3c_gpio_setpull() - set the state of a gpio pin pull resistor
 * @pin: The pin number to configure the pull resistor.
 * @pull: The configuration for the pull resistor.
 *
 * This function sets the state of the pull-{up,down} resistor for the
 * specified pin. It will return 0 if successful, or a negative error
 * code if the pin cannot support the requested pull setting.
 *
 * @pull is one of S3C_GPIO_PULL_NONE, S3C_GPIO_PULL_DOWN or S3C_GPIO_PULL_UP.
*/
extern int s3c_gpio_setpull(unsigned int pin, samsung_gpio_pull_t pull);

/**
 * s3c_gpio_getpull() - get the pull resistor state of a gpio pin
 * @pin: The pin number to get the settings for
 *
 * Read the pull resistor value for the specified pin.
*/
extern samsung_gpio_pull_t s3c_gpio_getpull(unsigned int pin);

/* configure `all` aspects of an gpio */

/**
 * s3c_gpio_cfgall_range() - configure range of gpio functtion and pull.
 * @start: The gpio number to start at.
 * @nr: The number of gpio to configure from @start.
 * @cfg: The configuration to use
 * @pull: The pull setting to use.
 *
 * Run s3c_gpio_cfgpin() and s3c_gpio_setpull() over the gpio range starting
 * @gpio and running for @size.
 *
 * @sa s3c_gpio_cfgpin
 * @sa s3c_gpio_setpull
 * @sa s3c_gpio_cfgpin_range
 */
extern int s3c_gpio_cfgall_range(unsigned int start, unsigned int nr,
                 unsigned int cfg, samsung_gpio_pull_t pull);

static inline int s3c_gpio_cfgrange_nopull(unsigned int pin, unsigned int size,
                       unsigned int cfg)
{
    return s3c_gpio_cfgall_range(pin, size, cfg, S3C_GPIO_PULL_NONE);
}

/* Define values for the drvstr available for each gpio pin.
 *
 * These values control the value of the output signal driver strength,
 * configurable on most pins on the S5P series.
 */
#define S5P_GPIO_DRVSTR_LV1 ((__force s5p_gpio_drvstr_t)0x0)
#ifdef CONFIG_SOC_EXYNOS5260
#define S5P_GPIO_DRVSTR_LV2     ((__force s5p_gpio_drvstr_t)0x1)
#define S5P_GPIO_DRVSTR_LV3     ((__force s5p_gpio_drvstr_t)0x2)
#else
#define S5P_GPIO_DRVSTR_LV2 ((__force s5p_gpio_drvstr_t)0x2)
#define S5P_GPIO_DRVSTR_LV3 ((__force s5p_gpio_drvstr_t)0x1)
#endif
#define S5P_GPIO_DRVSTR_LV4 ((__force s5p_gpio_drvstr_t)0x3)

/**
 * s5c_gpio_get_drvstr() - get the driver streght value of a gpio pin
 * @pin: The pin number to get the settings for
 *
 * Read the driver streght value for the specified pin.
*/
extern s5p_gpio_drvstr_t s5p_gpio_get_drvstr(unsigned int pin);

/**
 * s3c_gpio_set_drvstr() - set the driver streght value of a gpio pin
 * @pin: The pin number to configure the driver streght value
 * @drvstr: The new value of the driver strength
 *
 * This function sets the driver strength value for the specified pin.
 * It will return 0 if successful, or a negative error code if the pin
 * cannot support the requested setting.
*/
extern int s5p_gpio_set_drvstr(unsigned int pin, s5p_gpio_drvstr_t drvstr);

/* Define values for the power down configuration available for each gpio pin.
 *
 * These values control the state of the power down configuration resistors
 * available on most pins on the S5P series.
 */
#define S5P_GPIO_PD_OUTPUT0 ((__force s5p_gpio_pd_cfg_t)0x00)
#define S5P_GPIO_PD_OUTPUT1 ((__force s5p_gpio_pd_cfg_t)0x01)
#define S5P_GPIO_PD_INPUT   ((__force s5p_gpio_pd_cfg_t)0x02)
#define S5P_GPIO_PD_PREV_STATE  ((__force s5p_gpio_pd_cfg_t)0x03)

extern s5p_gpio_data_t s5p_gpio_get_data(unsigned int pin);
extern int s5p_gpio_set_data(unsigned int pin, s5p_gpio_data_t drvstr);

/* Define values for the power down configuration available for each gpio pin.
 *
 * These values control the state of the power down configuration resistors
 * available on most pins on the S5P series.
 */
#define S5P_GPIO_DATA0      ((__force s5p_gpio_data_t)0x0)
#define S5P_GPIO_DATA1      ((__force s5p_gpio_data_t)0x1)

/**
 * s5p_gpio_set_pd_cfg() - set the configuration of a gpio power down mode
 * @pin: The pin number to configure the pull resistor.
 * @pd_cfg: The configuration for the pwer down mode configuration register.
 *
 * This function sets the configuration of the power down mode resistor for the
 * specified pin. It will return 0 if successful, or a negative error
 * code if the pin cannot support the requested power down mode.
 *
*/
extern int s5p_gpio_set_pd_cfg(unsigned int pin, s5p_gpio_pd_cfg_t pd_cfg);

/**
 * s5p_gpio_get_pd_cfg() - get the power down mode configuration of a gpio pin
 * @pin: The pin number to get the settings for
 *
 * Read the power down mode resistor value for the specified pin.
*/
extern s5p_gpio_pd_cfg_t s5p_gpio_get_pd_cfg(unsigned int pin);

/* Define values for the power down pull-{up,down} available for each gpio pin.
 *
 * These values control the state of the power down mode pull-{up,down}
 * resistors available on most pins on the S5P series.
 */
#define S5P_GPIO_PD_UPDOWN_DISABLE  ((__force s5p_gpio_pd_pull_t)0x00)
#define S5P_GPIO_PD_DOWN_ENABLE     ((__force s5p_gpio_pd_pull_t)0x01)
#define S5P_GPIO_PD_UP_ENABLE       ((__force s5p_gpio_pd_pull_t)0x03)

/**
 * s5p_gpio_set_pd_pull() - set the pull-{up,down} of a gpio pin power down mode
 * @pin: The pin number to configure the pull resistor.
 * @pd_pull: The configuration for the power down mode pull resistor.
 *
 * This function sets the configuration of the pull-{up,down} resistor for the
 * specified pin. It will return 0 if successful, or a negative error
 * code if the pin cannot support the requested pull setting.
 *
 */
extern int s5p_gpio_set_pd_pull(unsigned int pin, s5p_gpio_pd_pull_t pd_pull);

/**
 * s5p_gpio_get_pd_pull() - get the power down pull resistor config of gpio pin
 * @pin: The pin number to get the settings for
 *
 * Read the power mode pull resistor value for the specified pin.
 */
extern s5p_gpio_pd_pull_t s5p_gpio_get_pd_pull(unsigned int pin);

/**
 * s5p_register_gpio_interrupt() - register interrupt support for a gpio group
 * @pin: The pin number from the group to be registered
 *
 * This function registers gpio interrupt support for the group that the
 * specified pin belongs to.
 *
 * The total number of gpio pins is quite large ob s5p series. Registering
 * irq support for all of them would be a resource waste. Because of that the
 * interrupt support for standard gpio pins is registered dynamically.
 *
 * It will return the irq number of the interrupt that has been registered
 * or -ENOMEM if no more gpio interrupts can be registered. It is allowed
 * to call this function more than once for the same gpio group (the group
 * will be registered only once).
 */
extern int s5p_register_gpio_interrupt(int pin);

/** s5p_register_gpioint_bank() - add gpio bank for further gpio interrupt
 * registration (see s5p_register_gpio_interrupt function)
 * @chain_irq: chained irq number for the gpio int handler for this bank
 * @start: start gpio group number of this bank
 * @nr_groups: number of gpio groups handled by this bank
 *
 * This functions registers initial information about gpio banks that
 * can be later used by the s5p_register_gpio_interrupt() function to
 * enable support for gpio interrupt for particular gpio group.
 */
#ifdef CONFIG_S5P_GPIO_INT
extern int s5p_register_gpioint_bank(int chain_irq, int start, int nr_groups);
#else
#define s5p_register_gpioint_bank(chain_irq, start, nr_groups) do { } while (0)
#endif

/**
 * exynos_set_lpa_pdn() - Help to set GPIO power down register before
 * entering LPA(Low Power Audio) mode. This mode is implemented as a
 * kind of cpuidle state(C-state).
 * In this mode, Normal GPIO cannot sustain configuration and need to
 * configure power down register.
 */
extern void exynos_set_lpa_pdn(unsigned int gpio_end);

#endif /* __PLAT_GPIO_CFG_H */













/*
 * Generic GPIO API implementation for Alpha.
 *
 * A stright copy of that for PowerPC which was:
 *
 * Copyright (c) 2007-2008  MontaVista Software, Inc.
 *
 * Author: Anton Vorontsov <avorontsov@ru.mvista.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#ifndef _ASM_ALPHA_GPIO_H
#define _ASM_ALPHA_GPIO_H

#include <linux/errno.h>
#include <asm-generic/gpio.h>

#ifdef CONFIG_GPIOLIB

/*
 * We don‘t (yet) implement inlined/rapid versions for on-chip gpios.
 * Just call gpiolib.
 */
static inline int gpio_get_value(unsigned int gpio)
{
    return __gpio_get_value(gpio);
}

static inline void gpio_set_value(unsigned int gpio, int value)
{
    __gpio_set_value(gpio, value);
}

static inline int gpio_cansleep(unsigned int gpio)
{
    return __gpio_cansleep(gpio);
}

static inline int gpio_to_irq(unsigned int gpio)
{
    return __gpio_to_irq(gpio);
}

static inline int irq_to_gpio(unsigned int irq)
{
    return -EINVAL;
}

#endif /* CONFIG_GPIOLIB */

#endif /* _ASM_ALPHA_GPIO_H */