s3c2410_gpio_cfgpin函數(shù)解析

位置:/linux-2.6.32.2/arch/arm/plat-s3c24xx/gpio.c

函數(shù)內(nèi)容：

void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function)
{
void __iomem *base =S3C24XX_GPIO_BASE(pin);
unsigned long mask;
unsigned long con;
unsigned long flags;

if (pin mask = 1 <}

else {
mask = 3 << S3C2410_GPIO_OFFSET(pin)*2;
}

switch (function) {
caseS3C2410_GPIO_LEAVE:
mask = 0;
function = 0;
break;

caseS3C2410_GPIO_INPUT:
caseS3C2410_GPIO_OUTPUT:
caseS3C2410_GPIO_SFN2:
caseS3C2410_GPIO_SFN3:
if (pin function -= 1;
function &= 1;
function <<= S3C2410_GPIO_OFFSET(pin);
} else {
function &= 3;
function <<= S3C2410_GPIO_OFFSET(pin)*2;
}
}

/* modify the specified register wwith IRQs off */

local_irq_save(flags);

con = __raw_readl(base + 0x00);
con &= ~mask;
con |= function;

__raw_writel(con, base + 0x00);

local_irq_restore(flags);
}

EXPORT_SYMBOL(s3c2410_gpio_cfgpin);

/***************************************************************************

首先確定一下各宏定義所在的位置和意義:

S3C24XX_GPIO_BASE(pin) -->

S3C2410_GPIO_OFFSET(pin)-->

S3C2410_GPIO_INPUT-->

S3C2410_GPIO_OUTPUT-->

S3C2410_GPIO_SFN2-->

S3C2410_GPIO_SFN3-->

以上宏都是在/linux2.6.32.2/arch/arm/mach-s3c2410/include/regs_gpio.h定義.

S3C2410_GPIO_BANKB-->

此宏的定義是在/linux-2.6.32.2/arch/arm/mach-s3c2410/include/mach/gpio-nrs.h中定義.

接下來，順序解析程序:

#define S3c2410_GPIO_BASE(pin) ((((pin) & ~31) >>1) +S3C24XX_VA_GPIO)

S3C24XX_VA_GPIO在/linux-2.6.32.2/arch/arm/plat-s3c24xx/include/plat/map.h中是這樣定義的:

S3C24XX_PA_GPIO在/linux-2.6.32.2/arch/arm/mach-s3c2410/include/mach/map.h中這樣定義:

而S3C2410_PA_GPIO在/linux-2.6.32.2/arch/arm/plat-s3c24xx/include/plat/map.h中這樣定義:

S3C24XX_PA_UART在中這樣定義:

而S3C2410_PA_UART在/linux-2.6.32.2/arch/arm/plat-s3c24xx/include/plat/map.h中這樣定義:

S3C24XX_VA_UART在linux-2.6.32.2/arch/arm/plat-s3c24xx/include/plat/map.h中這樣定義:

而S3C_VA_UART在linux-2.6.32.2/arch/arm/plat-s3c/include/plat/map.h中這樣定義：

由以上宏定義可以推出:

S3C24XX_VA_GPIO=((S3C24XX_PA_GPIO - S3C24XX_PA_UART) + S3C24XX_VA_UART)

=((0x56000000 - 0x50000000) + (0xF4000000 + 0x01000000))

= (0x06000000 + 0xF5000000)

= (0xFB000000)

這里假設(shè)設(shè)置GPB5引腳為輸出:

s3c2410_gpio_cfgpin(S3C2410_GPB(5),S3C2410_GPB_OUTPUT);

首先S3C2410_GPB(_nr)在/linux-2.6.32.2/arch/arm/mach-s3c2410/include/mach/gpio-nrs.h中這樣定義: