GPIO（GeneralPurpose Input/Output的缩写）就是芯片的引脚，引脚是可编程的可对引脚的工作模式进行设置：输入模式(检测输入信号)，输出模式(输出0或1)，高阻状态(常用于AD转换)，还有禁止或允许上内部下拉电阻(上拉：管脚通过电阻接高电平，下拉：管脚通过电阻接地，也可以外部接上拉或下拉电阻)，还有管脚复用等功能，即通过对内部寄存器的设置使引脚既可以工作在一般模式，作为普通的GPIO口使用，也可以工作在特殊模式，比如作为外部中断信号输入引脚等等。如果不设置GPIO引脚，CPU工作时有一个初始化模式，可以从datasheet（芯片手册）上了解。对GPIO的控制是编写驱动程序最常见和重要的一项工作内容。在Linux内核代码中，已经提供了针对三星S3C2410/S3C2440等芯片GPIO的控制。
*******************************************************************************
linux-2.6.30.4\arch\arm\plat-s3c\include\plat\ map-base.h
#defineS3C_ADDR_BASE (0xF4000000)
#ifndef __ASSEMBLY__
#define S3C_ADDR(x) ((void__iomem __force *)S3C_ADDR_BASE+ (x))
#else
#defineS3C_ADDR(x) (S3C_ADDR_BASE+ (x))
#endif
#define S3C_VA_IRQ S3C_ADDR(0x00000000) /* irq controller(s) */
#define S3C_VA_SYS S3C_ADDR(0x00100000) /* system control */
#define S3C_VA_MEM S3C_ADDR(0x00200000) /* system control */
#define S3C_VA_TIMER S3C_ADDR(0x00300000) /* timer block */
#define S3C_VA_WATCHDOG S3C_ADDR(0x00400000) /* watchdog */
#define S3C_VA_UART S3C_ADDR(0x01000000) /*UART */
linux-2.6.30.4\arch\arm\plat-s3c24xx\include\plat\ map.h
/* UARTs */
#defineS3C24XX_VA_UART S3C_VA_UART
#define S3C2410_PA_UART (0x50000000)
#define S3C24XX_SZ_UART SZ_1M
#define S3C_UART_OFFSET (0x4000)
UART映射后的虚拟地址是0xF4000000＋0x01000000
linux-2.6.30.4\arch\arm\plat-s3c24xx\include\plat\ map.h
/* GPIO ports */
#define S3C2410_PA_GPIO (0x56000000)
#defineS3C24XX_VA_GPIO ((S3C24XX_PA_GPIO- S3C24XX_PA_UART) + S3C24XX_VA_UART)//GPIO的虚拟地址
#define S3C24XX_SZ_GPIO SZ_1M
GPIO的基地址为 0xfb000000
S3C24XX_VA_GPIO在不同的linux版本中可能不一样，2.6.30.4是按照上面的方式，下图是2.6.22.6的实现方法
linux/include/asm-arm/arch-s3c2410/map.h
#ifndef __ASSEMBLY__
#define S3C2410_ADDR(x) ((void __iomem *)0xF0000000 + (x))
#else
#define S3C2410_ADDR(x) (0xF0000000 + (x))
#endif
#define S3C2400_ADDR(x) S3C2410_ADDR(x)
/* GPIO ports */
#define S3C24XX_VA_GPIO S3C2410_ADDR(0x00E00000)
#define S3C2400_PA_GPIO (0x15600000)
#define S3C2410_PA_GPIO (0x56000000)
#define S3C24XX_SZ_GPIO SZ_1M
|
arch/arm/mach-s3c2410/include/mach/regs-gpio.h
#defineS3C2410_GPIOREG(x) ((x) + S3C24XX_VA_GPIO)//在GPIO的虚拟地址上直接偏移
#define S3C24XX_GPIOREG2(x) ((x) + S3C24XX_VA_GPIO2)
linux-2.6.30.4/arch/arm/mach-s3c2410/include/mach/gpio-nrs.h
#defineS3C2410_GPIONO(bank,offset)((bank) + (offset))
#defineS3C2410_GPIO_BANKA (32*0)//每组最多32个端口
#define S3C2410_GPIO_BANKB (32*1)
#define S3C2410_GPIO_BANKC (32*2)
#define S3C2410_GPIO_BANKD (32*3)
#define S3C2410_GPIO_BANKE (32*4)
#define S3C2410_GPIO_BANKF (32*5)
#define S3C2410_GPIO_BANKG (32*6)
#define S3C2410_GPIO_BANKH (32*7)
arch/arm/mach-s3c2410/include/mach/regs-gpio.h
#defineS3C2410_GPACON S3C2410_GPIOREG(0x00)//A组GPIO的控制寄存器
#define S3C2410_GPADAT S3C2410_GPIOREG(0x04)//A组GPIO的数据寄存器
#define S3C2400_GPACON S3C2410_GPIOREG(0x00)
#define S3C2400_GPADAT S3C2410_GPIOREG(0x04)
#defineS3C2410_GPA0 S3C2410_GPIONO(S3C2410_GPIO_BANKA, 0)//A组GPIO的第0个的pin数
#define S3C2410_GPA0_OUT (0<<0)//设置A0为输出功能
#define S3C2410_GPA0_ADDR0 (1<<0)//设置A0作为地址线ADDR0
*******************************************************************************
#define S3C2410_GPBCON S3C2410_GPIOREG(0x10)
#define S3C2410_GPBDAT S3C2410_GPIOREG(0x14)
#define S3C2410_GPBUP S3C2410_GPIOREG(0x18)
#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 S3C2400_GPB0_DATA16 (0x02 << 0)
*******************************************************************************
#define S3C2410_GPCCON S3C2410_GPIOREG(0x20)
#define S3C2410_GPCDAT S3C2410_GPIOREG(0x24)
#define S3C2410_GPCUP S3C2410_GPIOREG(0x28)
#define S3C2410_GPC0 S3C2410_GPIONO(S3C2410_GPIO_BANKC, 0)
#define S3C2410_GPC0_INP (0x00<< 0)
#define S3C2410_GPC0_OUTP (0x01<< 0)
#define S3C2410_GPC0_LEND (0x02<< 0)
#define S3C2400_GPC0_VD0 (0x02<< 0)
*******************************************************************************
#define S3C2410_GPDCON S3C2410_GPIOREG(0x30)
#define S3C2410_GPDDAT S3C2410_GPIOREG(0x34)
#define S3C2410_GPDUP S3C2410_GPIOREG(0x38)
— Port A(GPA): 25-output port
— Port B(GPB): 11-input/out port
— Port C(GPC): 16-input/output port
— Port D(GPD): 16-input/output port
— Port E(GPE): 16-input/output port
— Port F(GPF): 8-input/output port
— Port G(GPG): 16-input/output port
— Port H(GPH): 9-input/output port
— Port J(GPJ): 13-input/output port
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
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
Register Address R/W Description Reset Value
GPCCON 0x56000020 R/W Configures the pins of port C 0x0
GPCDAT 0x56000024 R/W The data register for port C Undef.
GPCUP 0x56000028 R/W Pull-up disable register for port C 0x0
Reserved 0x5600002c – – –
Register Address R/W Description Reset Value
GPDCON 0x56000030 R/W Configures the pins of port D 0x0
GPDDAT 0x56000034 R/W The data register for port D Undef.
GPDUP 0x56000038 R/W Pull-up disable register for port D 0xf000
Reserved 0x5600003c – – – |
*******************************************************************************
void s3c2410_gpio_cfgpin(unsignedint pin, unsigned int function)// 其中参数pin是要配置的GPIO引脚，参数function是要配置的功能
{
void __iomem *base = S3C24XX_GPIO_BASE(pin);
unsignedlong mask;
unsignedlong con;
unsignedlong flags;
if(pin < S3C2410_GPIO_BANKB){
mask= 1 << S3C2410_GPIO_OFFSET(pin);
}else {
mask= 3 << S3C2410_GPIO_OFFSET(pin)*2;
}
//如果引脚为A端口之外GPIO端口时，它是用两位来配置具体的引脚，故掩码为2位
switch(function) {
caseS3C2410_GPIO_LEAVE:
mask= 0;
function= 0;
break;
caseS3C2410_GPIO_INPUT:
caseS3C2410_GPIO_OUTPUT:
caseS3C2410_GPIO_SFN2:
caseS3C2410_GPIO_SFN3:
if(pin < S3C2410_GPIO_BANKB){
function-= 1;
function&= 1;
function<<= S3C2410_GPIO_OFFSET(pin);
}else {
function&= 3;
function<<= S3C2410_GPIO_OFFSET(pin)*2;
}
}
/* modify thespecified register wwith IRQs off */
local_irq_save(flags);// 关中断
con = __raw_readl(base + 0x00);
con &= ~mask;
con |= function;
__raw_writel(con, base + 0x00);
local_irq_restore(flags);// 开中断
}
arch/arm/mach-s3c2410/include/mach/regs-gpio.h
#define S3C2410_GPIO_BASE(pin) ((((pin) & ~31) >> 1) + S3C24XX_VA_GPIO)
//每组GPIO的虚拟基地址（要先屏蔽最低的5位）根据端口编号pin，算出端口所在组的虚拟基址。((pin) & ~31)是去掉pin当中小于等于31的零头(清0低5位)，>>1的原因是每组GPIO中最多可以有32个端口，控制这些端口需要4个寄存器空间，4个寄存器空间就需要4*4=16个字节进行编址，32/16=2，左移一位刚好满足。也就是说，上一组端口和下一组端口的编号相差32，而控制寄存器的地址相差16。
#define S3C2410_GPIO_OFFSET(pin) ((pin) & 31)
//根据端口编号pin，算出端口所在组的偏移量。((pin) & 31)即去掉比31大的数
linux/arch/arm/plat-s3c24xx/gpio.c
s3c2410_gpio_cfgpin //配置端口的GPIO的功能
s3c2410_gpio_getcfg //读取功能配置
s3c2410_gpio_pullup //配置上拉电阻
s3c2410_modify_misccr //杂项配置
s3c2410_gpio_getirq //给定端口，转换出IRQ号
s3c2410_gpio_irqfilter //配置IRQ过滤使能与否
s3c2410_gpio_setpin //写数据到端口
s3c2410_gpio_getpin //从端口读数据
以下代码摘自Leds的驱动程序，旨在说明linux下如何访问寄存器
static unsigned long led_table [] =
{
S3C2410_GPB5,
S3C2410_GPB6,
S3C2410_GPB7,
S3C2410_GPB8,
};
/* 用来指定GPIO引脚的功能：输出 */
static unsigned int led_cfg_table [] =
{
S3C2410_GPB5_OUTP,
S3C2410_GPB6_OUTP,
S3C2410_GPB7_OUTP,
S3C2410_GPB8_OUTP,
};
static int gt2440_leds_ioctl(
structinode *inode,
structfile *file,
unsignedint cmd,
unsignedlong arg)
{
if(arg > 4)
{
return-EINVAL;
}
switch(cmd)
{
caseIOCTL_LED_ON:
//设置指定引脚的输出电平为0
s3c2410_gpio_setpin(led_table[arg], 0);
return0;
caseIOCTL_LED_OFF:
//设置指定引脚的输出电平为1
s3c2410_gpio_setpin(led_table[arg], 1);
return0;
default:
return-EINVAL;
}
}
static struct file_operations dev_fops = {
.owner = THIS_MODULE,
.ioctl = gt2440_leds_ioctl,
};
static struct miscdevice misc = {
.minor= MISC_DYNAMIC_MINOR,
.name= DEVICE_NAME,
.fops= &dev_fops,
};
static int __init dev_init(void)
{
intret;
inti;
for(i = 0; i < 4; i++)
{
s3c2410_gpio_cfgpin(led_table[i],led_cfg_table[i]);
s3c2410_gpio_setpin(led_table[i],0);// 设置相应GPIO口的值
}
ret= misc_register(&misc);
printk(DEVICE_NAME" initialized\n");
returnret;
}
static void __exit dev_exit(void)
{
misc_deregister(&misc);
}
module_init(dev_init);
module_exit(dev_exit); *******************************************************************************
