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分类:
2012-12-27 17:18:05
原文地址:值得参考的一篇linux gpio 作者:dyli2000
首先是代码中的几个宏定义:
2.6.31内核:arch/arm/mach-2410/include/mach/regs-gpio.h
#define S3C2410_GPIONO(bank,offset) ((bank) + (offset))
#define S3C2410_GPIO_BANKA (32*0)
#define S3C2410_GPIO_BANKB (32*1)
#define S3C2410_GPIO_BANKC (32*2)
....
#define S3C2410_GPIO_BASE(pin) ((((pin) & ~31) >> 1) + S3C24XX_VA_GPIO)
#define S3C2410_GPIO_OFFSET(pin) ((pin) & 31)
#define S3C2410_GPBCON S3C2410_GPIOREG(0x10)
#define S3C2410_GPBDAT S3C2410_GPIOREG(0x14)
#define S3C2410_GPBUP S3C2410_GPIOREG(0x18)
/* no i/o pin in port b can have value 3! */
#define S3C2410_GPB0 S3C2410_GPIONO(S3C2410_GPIO_BANKB, 0)
#define S3C2410_GPB0_INP (0x00 << 0)
#define S3C2410_GPB0_OUTP (0x01 << 0)
#define S3C2410_GPB0_TOUT0 (0x02 << 0)
#define S3C2410_GPB1 S3C2410_GPIONO(S3C2410_GPIO_BANKB, 1)
#define S3C2410_GPB1_INP (0x00 << 2)
#define S3C2410_GPB1_OUTP (0x01 << 2)
#define S3C2410_GPB1_TOUT1 (0x02 << 2)
....
driver中有这样的代码:
s3c2410_gpio_cfgpin(led_table[i], led_cfg_table[i]);
s3c2410_gpio_setpin(led_table[i], 1);
其中
static unsigned long led_table [] = {
S3C2410_GPB5,
S3C2410_GPB6,
S3C2410_GPB7,
S3C2410_GPB8,
};
static unsigned int led_cfg_table [] = {
S3C2410_GPB5_OUTP,
S3C2410_GPB6_OUTP,
S3C2410_GPB7_OUTP,
S3C2410_GPB8_OUTP,
};
2.6.31内核:arch/arm/plat-s3c24xx/gpio.c:
void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function)
{
void __iomem *base = S3C2410_GPIO_BASE(pin);
unsigned long mask;
unsigned long con;
unsigned long flags;
if (pin < S3C2410_GPIO_BANKB) {
mask = 1 << S3C2410_GPIO_OFFSET(pin);
} else {
mask = 3 << S3C2410_GPIO_OFFSET(pin)*2;
}
local_irq_save(flags);
con = __raw_readl(base + 0x00);
con &= ~mask;
con |= function;
__raw_writel(con, base + 0x00); //config the GPXCON
local_irq_restore(flags);
}
EXPORT_SYMBOL(s3c2410_gpio_cfgpin);
void s3c2410_gpio_setpin(unsigned int pin, unsigned int to)
{
void __iomem *base = S3C2410_GPIO_BASE(pin);
unsigned long offs = S3C2410_GPIO_OFFSET(pin);
unsigned long flags;
unsigned long dat;
local_irq_save(flags);
dat = __raw_readl(base + 0x04);
dat &= ~(1 << offs);
dat |= to << offs;
__raw_writel(dat, base + 0x04); //config the GPXDAT
local_irq_restore(flags);
}
EXPORT_SYMBOL(s3c2410_gpio_setpin);
===========================================================================================================
对传给s3c2410_gpio_cfgpin 函数的pin参数由来解释:pin就是如S3C2410_GPB0(表示B组第五个端口),S3C2410_GPA0之类的宏,而这些宏表示着什么呢?如宏S3C2410_GPB0就是通过宏
#define S3C2410_GPB0 S3C2410_GPIONO(S3C2410_GPIO_BANKB, 0)
得到的,S3C2410_GPIONO(S3C2410_GPIO_BANKB, 0)宏是这样定义的
#define S3C2410_GPIONO(bank,offset) ((bank) + (offset))
很明显,S3C2410_GPIONO(S3C2410_GPIO_BANKB, 0)就是计算两个参数的和,第一个参数表示第几组,第二个参数0表示0端口,如果是计算第一个端口的话,第二个参数就是1;
对于S3C2410_GPIO_BANKB宏的定义是
#define S3C2410_GPIO_BANKB (32*1)
而类似GPA的定义是
#define S3C2410_GPIO_BANKA (32*0)
所以最后算出来的S3C2410_GPB5的值是:37 = S3C2410_GPIO_BANKB + 5=32*1 + 5;
===========================================================================================================
关于s3c2410_gpio_cfgpin的第二个参数function其实是由宏定义的,如
#define S3C2410_GPB0_INP (0x00 << 0)
#define S3C2410_GPB0_OUTP (0x01 << 0)
#define S3C2410_GPB0_TOUT0 (0x02 << 0)
#define S3C2410_GPB1_INP (0x00 << 2)
#define S3C2410_GPB1_OUTP (0x01 << 2)
#define S3C2410_GPB1_TOUT1 (0x02 << 2)
他们是用来设置端口的功能的,就是设置GPACON、GPBCON、GPCCON、GPDCON等配置寄存器的,因为端口0的设置位占了两位,而端口1的设置为是紧接着的第3,4位(没有第0位的说法),所以要移2位。
===========================================================================================================
A
有个GPIO的虚拟地址base,接下来分析下面的:
#define S3C2410_GPIO_BASE(pin) ((((pin) & ~31) >> 1) + S3C24XX_VA_GPIO)
关于((pin) & ~31) >> 1)的计算:由上面算出的宏S3C2410_GPB5值37(既是pin值)来计算出((pin) & ~31) >> 1)的值,因为
pin = S3C2410_GPB5 = 37, 37 的二进制是10,0101,~31的二进制是10,0000所以(pin) & ~31) 的值是 32(0x20),((pin) & ~31) >> 1)的结果是16(0x10),其实无论是B组内的第几个端口,如果是B组端口的话, ((pin) & ~31) >> 1)的结果都是16(0x10),这就是S3C2410_GPIO_BASE(pin)的功能,即算出端口的基地址,~31主要是为了清除S3C2410_GPB5的后5位。
B
相对于
#define S3C2410_GPIO_BASE(pin) ((((pin) & ~31) >> 1) + S3C24XX_VA_GPIO)
有个
#define S3C2410_GPIO_OFFSET(pin) ((pin) & 31)
对比这两个宏,宏S3C2410_GPIO_OFFSET(pin)功能很明显了:计算出是组内的端口号,如S3C2410_GPB5算出的就是5了。
===========================================================================================================
关于S3C2410芯片的S3C24XX_VA_GPIO的计算
#define S3C24XX_VA_GPIO ((S3C24XX_PA_GPIO - S3C24XX_PA_UART) + S3C24XX_VA_UART)
#define S3C24XX_PA_GPIO S3C2410_PA_GPIO
#define S3C2410_PA_GPIO (0x56000000)
#define S3C24XX_PA_UART S3C2410_PA_UART
#define S3C2410_PA_UART (0x50000000)
#define S3C24XX_VA_UART S3C_VA_UART
#define S3C_VA_UART S3C_ADDR(0x01000000) /* UART */
#define S3C_ADDR(x) ((void __iomem __force *)S3C_ADDR_BASE + (x))
#define S3C_ADDR(x) (S3C_ADDR_BASE + (x))
#define S3C_ADDR_BASE (0xF4000000)
S3C24XX_VA_GPIO的结果是0xFB000000 = 0x56000000 - 0x50000000 + 0xF4000000 + 0x01000000
以上的宏是在2.6.31内核的。
===========================================================================================================
以下是一些访问通用I/O的方法:
void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function);
unsigned int s3c2410_gpio_getcfg(unsigned int pin);
void s3c2410_gpio_pullup(unsigned int pin, unsigned int to);
int s3c2410_gpio_getpull(unsigned int pin);
void s3c2410_gpio_setpin(unsigned int pin, unsigned int to);
unsigned int s3c2410_gpio_getpin(unsigned int pin);
unsigned int s3c2410_modify_misccr(unsigned int clear, unsigned int change);
int s3c2410_gpio_getirq(unsigned int pin);
===========================================================================================================
有以上对宏define S3C2410_GPIO_BASE(pin)的解释,可推断出
GPA基地址的是0x0+S3C24XX_VA_GPIO,GPB是0x10+S3C24XX_VA_GPIO,GPC是 0x20+S3C24XX_VA_GPIO...
为什么相邻的端口组地址相差0x10呢?
因为每一组端口都有四个寄存器,举GPA和GPB例子:
GPA:
Register |
Address |
R/W |
Description |
Reset Value |
GPACON |
0x56000000 |
R/W |
Configures the pins of port A |
0xffffff |
GPADAT |
0x56000004 |
R/W |
The data register for port A |
Undef. |
Reserved |
0x56000008 |
- |
|
Reserved Undef |
Reserved |
0x5600000c |
- |
|
Reserved Undef |
GPB:
Register |
Address |
R/W |
Description |
Reset Value |
GPBCON |
0x56000010 |
R/W |
Configures the pins of port B |
0x0 |
GPBDAT |
0x56000014 |
R/W |
The data register for port B. |
Undef |
GPBUP |
0x56000018 |
R/W |
pull-up disable register for port B |
0x0 |
Reserved |
0x5600001c |
|
|
|
由上两个表可知:每组四个寄存器是为了方便起见,组内相邻的寄存器之间相差4个字节,既是4*8=32bit,组与组之间相差0x10个字节。
==================================================================================================
关于宏
#define S3C2410_GPBCON S3C2410_GPIOREG(0x10)
#define S3C2410_GPBDAT S3C2410_GPIOREG(0x14)
#define S3C2410_GPBUP S3C2410_GPIOREG(0x18)
#define S3C2410_GPCCON S3C2410_GPIOREG(0x20)
#define S3C2410_GPCDAT S3C2410_GPIOREG(0x24)
#define S3C2410_GPCUP S3C2410_GPIOREG(0x28)
而S3C2410_GPIOREG的定义是:
#define S3C2410_GPIOREG(x) ((x) + S3C24XX_VA_GPIO)
所以而
GPBCON |
0x56000010 |
GPBDAT |
0x56000014 |
==========================================================================================================
其实想想这代码也不难理解,只是宏定义和函数的实现分散在kernel包的各个文件内,因此不太容易寻找。线索齐了后,就一目了然了。
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