Linux下GPIO驱动介绍文章

发布时间：2021-12-22 12:54:18 所属栏目：PHP教程来源：互联网

导读：注意：在/arch/arm/mach-s3c2410/include/mach/gpio-fns.h源代码中有如下说明： 16/* These functions are in the to-be-removed category and it is strongly 17 * encouraged not to use these in new code. They will be marked deprecated 18 * very soo

注意：在/arch/arm/mach-s3c2410/include/mach/gpio-fns.h源代码中有如下说明：

16/* These functions are in the to-be-removed category and it is strongly
17 * encouraged not to use these in new code. They will be marked deprecated
18 * very soon.
19 *
20 * Most of the functionality can be either replaced by the gpiocfg calls
21 * for the s3c platform or by the generic GPIOlib API.
22 *
23 * As of 2.6.35-rc, these will be removed, with the few drivers using them
24 * either replaced or given a wrapper until the calls can be removed.
25*/

该头文件包括：

static inline void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int cfg)

该函数直接使用

linux/arch/arm/plat-s3c/gpio-config.c中的

int s3c_gpio_cfgpin(unsigned int pin, unsigned int config)

即可

***************************************************************************

首先看一下设备初始化程序：

85 /*
86 * 设备初始化
87 */
88 static int __init dev_init(void)
89 {
90 int ret;
91 int i;
92 for (i = 0; i < 4; i++) {
93 //设置 LED 对应的端口寄存器为输出(OUTPUT)
94         if (s3c_gpio_cfgpin(led_table[i], led_cfg_table[i])<0)

                       printk(KERN_INFO "config pin %d failed", i);

95 printk(KERN_INFO "config pin %d failed", i);

95 //设置 LED 对应的端口寄存器为低电平输出，在模块加载> 结束后，四个 LED 应该是全部都是发光
96 状态
97         s3c2410_gpio_setpin(led_table[i], 0);
98 }
99 ret = misc_register(&misc); //注册设备
100 printk (DEVICE_NAME"/tinitialized/n"); //打印初始化信息
101 return ret;
102 }

可以看到，这里涉及到两个函数，分别是s3c2410_gpio_cfgpin,s3c2410_gpio_setpin，这两个函数分别对四个LED进行配置，从函数名来看，cfgpin对引脚寄存器状态进行配置，而setpin应该是对寄存器数据值进行配置，我们在分析函数之前先弄清楚传入的参数到底是什么。

led_table[i]
28 //LED 对应的 GPIO 端口列表
29 static unsigned long led_table [] = {
30     S3C2410_GPB(5),
31     S3C2410_GPB(6),
32     S3C2410_GPB(7),
33     S3C2410_GPB(8),
34 };

这里S3C2410_GPB宏定义在mach/gpio-nrs.h中
/* GPIO bank sizes */
#define S3C2410_GPIO_A_NR (32)
#define S3C2410_GPIO_B_NR (32)
#define S3C2410_GPIO_C_NR (32)
#define S3C2410_GPIO_D_NR (32)
#define S3C2410_GPIO_E_NR (32)
#define S3C2410_GPIO_F_NR (32)
#define S3C2410_GPIO_G_NR (32)
#define S3C2410_GPIO_H_NR (32)
#define S3C2410_GPIO_J_NR (32) /* technically 16. */
#define S3C2410_GPIO_K_NR (32) /* technically 16. */
#define S3C2410_GPIO_L_NR (32) /* technically 15. */
#define S3C2410_GPIO_M_NR (32) /* technically 2. */

#if CONFIG_S3C_GPIO_SPACE != 0
#error CONFIG_S3C_GPIO_SPACE cannot be zero at the moment
#endif

#define S3C2410_GPIO_NEXT(__gpio) /
((__gpio##_START) + (__gpio##_NR) + CONFIG_S3C_GPIO_SPACE + 0)

//这里的CONFIG_S3C_GPIO_SPAC是内核配置选项，在.config中可以找到，我的配置为：

CONFIG_S3C_GPIO_SPACE = 0

enum s3c_gpio_number {
S3C2410_GPIO_A_START = 0,
S3C2410_GPIO_B_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_A),
S3C2410_GPIO_C_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_B),
S3C2410_GPIO_D_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_C),
S3C2410_GPIO_E_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_D),
S3C2410_GPIO_F_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_E),
S3C2410_GPIO_G_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_F),
S3C2410_GPIO_H_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_G),
S3C2410_GPIO_J_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_H),
S3C2410_GPIO_K_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_J),
S3C2410_GPIO_L_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_K),
S3C2410_GPIO_M_START = S3C2410_GPIO_NEXT(S3C2410_GPIO_L),
};

#define S3C2410_GPB(_nr)    (S3C2410_GPIO_B_START + (_nr))

因此，以S3C2410_GPB(5)为例，其宏展开为：

S3C2410_GPIO_NEXT(S3C2410_GPIO_A) +5 =>

(S3C2410_GPIO_A_START + S3C2410_GPIO_A_NR + CONFIG_S3C_GPIO_SPACE + 0) + 5 =>

很显然， S3C2410_GPB(5)就是从GPA的首地址+GPA个数+GPB的offset就是当前GPB的IO偏移量，即

0+32+5=37, 同理

          S3C2410_GPB(0) 相当于 32

30     S3C2410_GPB(5) 相当于 37
31     S3C2410_GPB(6) 相当于 38
32     S3C2410_GPB(7) 相当于 39
33     S3C2410_GPB(8) 相当于 40

***************************************************************************

led_cfg_table[i]

36 //LED 对应端口将要输出的状态列表
37 static unsigned int led_cfg_table [] = {
38 S3C2410_GPIO_OUTPUT,
39 S3C2410_GPIO_OUTPUT,
40 S3C2410_GPIO_OUTPUT,
41 S3C2410_GPIO_OUTPUT,
42 };
S3C2410_GPIO_OUTPUT定义在mach/regs-gpio.h

#define S3C2410_GPIO_LEAVE (0xFFFFFFFF)                                             // 最后两位是设置，11表示RESERVE
#define S3C2410_GPIO_INPUT (0xFFFFFFF0) /* not available on A */        // 最后两位是设置，00表示INPUT

#define S3C2410_GPIO_OUTPUT (0xFFFFFFF1)                                         // 最后两位是设置，01表示OUTPUT
#define S3C2410_GPIO_IRQ (0xFFFFFFF2) /* not available for all */
#define S3C2410_GPIO_SFN2 (0xFFFFFFF2) /* bank A => addr/cs/nand */
#define S3C2410_GPIO_SFN3 (0xFFFFFFF3) /* not available on A */

***************************************************************************

根据前面的分析，s3c2410传入了当前GPIO的偏移地址，以及OUTPUT状态

现在我们深入前面的两个函数：

定义在linux/arch/arm/plat-s3c/gpio-config.c
int s3c_gpio_cfgpin(unsigned int pin, unsigned int config)
{
struct s3c_gpio_chip *chip = s3c_gpiolib_getchip(pin);   //得到对应GPIO结构体首指针，里面包含了该GPIO的各种参数
unsigned long flags;
int offset;
int ret;

if (!chip)
     return -EINVAL;   // 没找到的话，返回invalid

offset = pin - chip->chip.base;    // 否则offset等于该GPIO引脚相对于GPX（0）的偏移量，每个偏移1

s3c_gpio_lock(chip, flags);    // 自旋锁锁住该GPIO，通过chip指针指向lock,看下面的define和图
ret = s3c_gpio_do_setcfg(chip, offset, config);    //设置该GPIO状态寄存器的数值为config
s3c_gpio_unlock(chip, flags); // 解锁

// 自旋锁操作
/* locking wrappers to deal with multiple access to the same gpio bank */
//#define s3c_gpio_lock(_oc, _fl) spin_lock_irqsave(&(_oc)->lock, _fl)
//#define s3c_gpio_unlock(_oc, _fl) spin_unlock_irqrestore(&(_oc)->lock, _fl)

//s3c_gpio_do_setcfg操作
static inline int s3c_gpio_do_setcfg(struct s3c_gpio_chip *chip,
unsigned int off, unsigned int config)
{
     return (chip->config->set_config)(chip, off, config);
}

//这里的set_config是一个函数指针，由后面的分析知道，如果针对GPA,该函数指针指向s3c_gpio_setcfg_s3c24xx_a , 如果针对GPX应该是指向s3c_gpio_setcfg_s3c24xx——但发现，如果是其他GPX，根本没有定义set_config!!! （这个问题已经解决，见后文s3c24xx_gpiolib_init函数，事实上，其余的config的确指向s3c_gpio_do_setcfg函数）

struct s3c_gpio_cfg s3c24xx_gpiocfg_default = {
           .set_config = s3c_gpio_setcfg_s3c24xx,
           .get_config = s3c_gpio_getcfg_s3c24xx,
};

int s3c_gpio_setcfg_s3c24xx_a(struct s3c_gpio_chip *chip, unsigned int off, unsigned int cfg)
{
void __iomem *reg = chip->base;   // GPXCON的物理基地址
unsigned int shift = off;    // 每个GPA对应一位
u32 con;

if (s3c_gpio_is_cfg_special(cfg)) {     //OUTPUT状态是否为(0xfffffffX)，是，返回1
         cfg &= 0xf; // cfg = 0xX

  /* Map output to 0, and SFN2 to 1 */ 本实验不会运行到这
cfg -= 1;
if (cfg > 1)
        return -EINVAL;

cfg <<= shift;
}

con = __raw_readl(reg);     // 先读出该GPXCON的值，32位
con &= ~(0x1 << shift);     //
con |= cfg;                         //
__raw_writel(con, reg);    // 将新值写入GPXCON

PS:

#define __raw_writeb(v,a) (__chk_io_ptr(a), *(volatile unsigned char __force *)(a) = (v))
#define __raw_writew(v,a) (__chk_io_ptr(a), *(volatile unsigned short __force *)(a) = (v))
#define __raw_writel(v,a) (__chk_io_ptr(a), *(volatile unsigned int __force *)(a) = (v))

#define __raw_readb(a) (__chk_io_ptr(a), *(volatile unsigned char __force *)(a))
#define __raw_readw(a) (__chk_io_ptr(a), *(volatile unsigned short __force *)(a))
#define __raw_readl(a) (__chk_io_ptr(a), *(volatile unsigned int __force *)(a))

return 0;
}

如果针对GPX情况

int s3c_gpio_setcfg_s3c24xx(struct s3c_gpio_chip *chip,
unsigned int off, unsigned int cfg)
{
void __iomem *reg = chip->base;
unsigned int shift = off * 2;    // 每个GPX对应2位
u32 con;

if (s3c_gpio_is_cfg_special(cfg)) {
          cfg &= 0xf;
if (cfg > 3)
          return -EINVAL;

  cfg <<= shift;        // 将cfg的0,1两位左移offset
}

con = __raw_readl(reg);         // 读对应的GPXCON值
con &= ~(0x3 << shift);          // 将GPXCON（pin）的两bits请0
con |= cfg;                               // 设置config值
__raw_writel(con, reg);           // 写入新的GPXCON

return 0;
}

return ret;
}                // end s3c_gpio_cfgpin

这里涉及到了一个重要的数据结构，s3c_gpio_chip，此数据结构比较复杂，我贴出这个数据结构的结构图：

、

这个重要的数据结构中可以记录每个GPIO所需要的所有数据，后面会遇到的s3c24xx_gpios[]结构体就是该结构体的集合，描述了芯片中所有的GPIO端口，之后我们需要时时回头看看这个结构。

我们先来看s3c_gpiolib_getchip ，它实现了返回对应pin值的GPIO结构体首指针的功能

#include<mach/gpio-core.h>

static inline struct s3c_gpio_chip *s3c_gpiolib_getchip(unsigned int pin)
{
struct s3c_gpio_chip *chip;

if (pin > S3C_GPIO_END)    //如果超过GPJ(32)就return NULL

     return NULL;

chip = &s3c24xx_gpios[pin/32];     //根据偏移，计算出对应pin的GPIO结构体指针
     return ((pin - chip->chip.base) < chip->chip.ngpio) ? chip : NULL;

     // 这里验证，如果pin偏移超过了GPIO的个数，说明出错了，否则就返回该GPIO的结构体指针
}

回想以下之前s3c2410_gpio_cfgpin中，我们传入的参数是led_table[i]和 led_cfg_table[i]，

/* GPIO sizes for various SoCs:
*
*                  2442
* 2410 2412 2440 2443 2416
* ---- ---- ---- ---- ----
* A 23     22     25      16      25
* B 11    11     11      11        9
* C 16    15     16      16      16
* D 16   16      16      16      16
* E 16    16     16       16      16
* F 8        8       8         8       8
* G16    16     16       16       8
* H 11    11      9       15      15
* J --      --     13       16       --
* K --     --      --        --       16
* L --      --      --       15        7
* M --     --      --         2        2
*/

struct s3c_gpio_chip s3c24xx_gpios[] = {
[0] = {
.base = S3C2410_GPACON, // datasheet上地址为0x56000000

//#define S3C2410_GPACON     S3C2410_GPIOREG(0x00)

#define S3C2410_GPIOREG(x) ((x) + S3C24XX_VA_GPIO)

#define S3C24XX_VA_GPIO     ((S3C24XX_PA_GPIO - S3C24XX_PA_UART) + S3C24XX_VA_UART)

S3C24XX_PA_GPIO相当于(0x15600000)

S3C24XX_PA_UART相当于(0x15000000)

#define S3C_VA_UART    S3C_ADDR(0x01000000)    /* UART */

#define S3C_ADDR_BASE 0xF6000000

#ifndef __ASSEMBLY__
#define S3C_ADDR(x) ((void __iomem __force *)S3C_ADDR_BASE + (x))
#else
#define S3C_ADDR(x) (S3C_ADDR_BASE + (x))
#endif

0x15600000-15000000+F7000000 这里的S3C2410_GPACON应该怎么算？

.pm = __gpio_pm(&s3c_gpio_pm_1bit),
.config = &s3c24xx_gpiocfg_banka,   // 设置GPIO的函数指针

                     static struct s3c_gpio_cfg s3c24xx_gpiocfg_banka = {
                         .set_config = s3c_gpio_setcfg_s3c24xx_a,
                         .get_config = s3c_gpio_getcfg_s3c24xx_a,
                      };
.chip = {
.base = S3C2410_GPA(0),   //基地址，也是偏移量
.owner = THIS_MODULE,
.label = "GPIOA",
.ngpio = 24,
.direction_input = s3c24xx_gpiolib_banka_input,
.direction_output = s3c24xx_gpiolib_banka_output,
},
},
[1] = {
.base = S3C2410_GPBCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPB(0),
.owner = THIS_MODULE,
.label = "GPIOB",
.ngpio = 16,
},
},
[2] = {
.base = S3C2410_GPCCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPC(0),
.owner = THIS_MODULE,
.label = "GPIOC",
.ngpio = 16,
},
},
[3] = {
.base = S3C2410_GPDCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPD(0),
.owner = THIS_MODULE,
.label = "GPIOD",
.ngpio = 16,
},
},
[4] = {
.base = S3C2410_GPECON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPE(0),
.label = "GPIOE",
.owner = THIS_MODULE,
.ngpio = 16,
},
},
[5] = {
.base = S3C2410_GPFCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPF(0),
.owner = THIS_MODULE,
.label = "GPIOF",
.ngpio = 8,
.to_irq = s3c24xx_gpiolib_bankf_toirq,
},
},
[6] = {
.base = S3C2410_GPGCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.irq_base = IRQ_EINT8,
.chip = {
.base = S3C2410_GPG(0),
.owner = THIS_MODULE,
.label = "GPIOG",
.ngpio = 16,
.to_irq = samsung_gpiolib_to_irq,
},
}, {
.base = S3C2410_GPHCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPH(0),
.owner = THIS_MODULE,
.label = "GPIOH",
.ngpio = 11,
},
},
/* GPIOS for the S3C2443 and later devices. */2440用不到
{
.base = S3C2440_GPJCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPJ(0),
.owner = THIS_MODULE,
.label = "GPIOJ",
.ngpio = 16,
},
}, {
.base = S3C2443_GPKCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPK(0),
.owner = THIS_MODULE,
.label = "GPIOK",
.ngpio = 16,
},
}, {
.base = S3C2443_GPLCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPL(0),
.owner = THIS_MODULE,
.label = "GPIOL",
.ngpio = 15,
},
}, {
.base = S3C2443_GPMCON,
.pm = __gpio_pm(&s3c_gpio_pm_2bit),
.chip = {
.base = S3C2410_GPM(0),
.owner = THIS_MODULE,
.label = "GPIOM",
.ngpio = 2,
},
},
};

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