下面我们自己编写I2C总线驱动，先看下内核的总线驱动怎么写的。 参考内核自带的适配器adapter，搜索配置文件
i2c-s3c2410.c 初始化函数i2c_adap_s3c_init看起
代码语言：javascript复制static int __init i2c_adap_s3c_init(void)
{
return platform_driver_register(&s3c24xx_i2c_driver);
}platform_driver_register
代码语言：javascript复制int platform_driver_register(struct platform_driver *drv)
{
drv->driver.bus = &platform_bus_type;
if (drv->probe)
drv->driver.probe = platform_drv_probe;
if (drv->remove)
drv->driver.remove = platform_drv_remove;
if (drv->shutdown)
drv->driver.shutdown = platform_drv_shutdown;
return driver_register(&drv->driver);
}s3c24xx_i2c_probe
代码语言：javascript复制static int s3c24xx_i2c_probe(struct platform_device *pdev)
{
struct s3c24xx_i2c *i2c;
struct s3c2410_platform_i2c *pdata = NULL;
struct resource *res;
int ret;
........
/*分配设置构造I2C adap*/
strlcpy(i2c->adap.name, "s3c2410-i2c", sizeof(i2c->adap.name));
i2c->adap.owner = THIS_MODULE;
i2c->adap.algo = &s3c24xx_i2c_algorithm;
i2c->adap.retries = 2;
i2c->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
i2c->tx_setup = 50;
........
of_i2c_register_devices(&i2c->adap);//注册函数s3c24xx_i2c_algorithm
代码语言：javascript复制static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
.master_xfer = s3c24xx_i2c_xfer,//重点！底层发送操作
.functionality = s3c24xx_i2c_func,//返回适配器支持的功能
};读写时序参考下图和裸机源码
源码如下：
代码语言：javascript复制#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/of_i2c.h>
#include <linux/of_gpio.h>
#include <plat/gpio-cfg.h>
#include <mach/regs-gpio.h>
#include <asm/irq.h>
#include <plat/regs-iic.h>
#include <plat/iic.h>
//#define PRINTK printk 参考裸板程序
#define PRINTK(...)
enum s3c24xx_i2c_state {
STATE_IDLE,
STATE_START,
STATE_READ,
STATE_WRITE,
STATE_STOP
};
struct s3c2440_i2c_regs {
unsigned int iiccon;
unsigned int iicstat;
unsigned int iicadd;
unsigned int iicds;
unsigned int iiclc;
};
struct s3c2440_i2c_xfer_data {
struct i2c_msg *msgs;
int msn_num;//当前消息的数量
int cur_msg;//当前传输的消息
int cur_ptr;
int state;
int err;
wait_queue_head_t wait;
};
static struct s3c2440_i2c_xfer_data s3c2440_i2c_xfer_data;
static struct s3c2440_i2c_regs *s3c2440_i2c_regs;
static void s3c2440_i2c_start(void)
{
s3c2440_i2c_xfer_data.state = STATE_START;
if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
{
s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->addr << 1;
s3c2440_i2c_regs->iicstat = 0xb0; // 主机接收，启动
}
else /* 写 */
{
s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->addr << 1;
s3c2440_i2c_regs->iicstat = 0xf0; // 主机发送，启动
}
}
static void s3c2440_i2c_stop(int err)
{
s3c2440_i2c_xfer_data.state = STATE_STOP;
s3c2440_i2c_xfer_data.err = err;
PRINTK("STATE_STOP, err = %dn", err);
if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
{
// 下面两行恢复I2C操作，发出P信号
s3c2440_i2c_regs->iicstat = 0x90;
s3c2440_i2c_regs->iiccon = 0xaf;
ndelay(50); // 等待一段时间以便P信号已经发出
}
else /* 写 */
{
// 下面两行用来恢复I2C操作，发出P信号
s3c2440_i2c_regs->iicstat = 0xd0;
s3c2440_i2c_regs->iiccon = 0xaf;
ndelay(50); // 等待一段时间以便P信号已经发出
}
/* 唤醒 */
wake_up(&s3c2440_i2c_xfer_data.wait);
}
static int s3c2440_i2c_xfer(struct i2c_adapter *adap,
struct i2c_msg *msgs, int num)
{
unsigned long timeout;
/* 把num个msg的I2C数据发送出去/读进来 */
s3c2440_i2c_xfer_data.msgs = msgs;
s3c2440_i2c_xfer_data.msn_num = num;
s3c2440_i2c_xfer_data.cur_msg = 0;
s3c2440_i2c_xfer_data.cur_ptr = 0;
s3c2440_i2c_xfer_data.err = -ENODEV;
s3c2440_i2c_start();
/* 休眠 */
timeout = wait_event_timeout(s3c2440_i2c_xfer_data.wait, (s3c2440_i2c_xfer_data.state == STATE_STOP), HZ * 5);
if (0 == timeout)
{
printk("s3c2440_i2c_xfer time outn");
return -ETIMEDOUT;
}
else
{
return s3c2440_i2c_xfer_data.err;
}
}
static u32 s3c2440_i2c_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
}
static const struct i2c_algorithm s3c2440_i2c_algo = {
// .smbus_xfer = ,
.master_xfer = s3c2440_i2c_xfer,
.functionality = s3c2440_i2c_func,
};
/* 1. 分配/设置i2c_adapter
*/
static struct i2c_adapter s3c2440_i2c_adapter = {
.name = "s3c2440_100ask",
.algo = &s3c2440_i2c_algo,
.owner = THIS_MODULE,
};
static int isLastMsg(void)
{
return (s3c2440_i2c_xfer_data.cur_msg == s3c2440_i2c_xfer_data.msn_num - 1);
}
static int isEndData(void)
{
return (s3c2440_i2c_xfer_data.cur_ptr >= s3c2440_i2c_xfer_data.msgs->len);
}
static int isLastData(void)
{
return (s3c2440_i2c_xfer_data.cur_ptr == s3c2440_i2c_xfer_data.msgs->len - 1);
}
static irqreturn_t s3c2440_i2c_xfer_irq(int irq, void *dev_id)
{
unsigned int iicSt;
iicSt = s3c2440_i2c_regs->iicstat;
if(iicSt & 0x8){ printk("Bus arbitration failednr"); }
switch (s3c2440_i2c_xfer_data.state)
{
case STATE_START : /* 发出S和设备地址后,产生中断 */
{
PRINTK("Startn");
/* 如果没有ACK, 返回错误 */
if (iicSt & S3C2410_IICSTAT_LASTBIT)
{
s3c2440_i2c_stop(-ENODEV);
break;
}
if (isLastMsg() && isEndData())
{
s3c2440_i2c_stop(0);
break;
}
/* 不是最后一个消息，进入下一个状态 */
if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
{
s3c2440_i2c_xfer_data.state = STATE_READ;
goto next_read;
}
else
{
s3c2440_i2c_xfer_data.state = STATE_WRITE;
}
}
case STATE_WRITE:
{
PRINTK("STATE_WRITEn");
/* 如果没有ACK, 返回错误 */
if (iicSt & S3C2410_IICSTAT_LASTBIT)
{
s3c2440_i2c_stop(-ENODEV);
break;
}
if (!isEndData()) /* 如果当前msg还有数据要发送 */
{
s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr];
s3c2440_i2c_xfer_data.cur_ptr ;
// 将数据写入IICDS后，需要一段时间才能出现在SDA线上
ndelay(50);
s3c2440_i2c_regs->iiccon = 0xaf; // 恢复I2C传输
break;
}
else if (!isLastMsg())
{
/* 开始处理下一个消息 */
s3c2440_i2c_xfer_data.msgs ;
s3c2440_i2c_xfer_data.cur_msg ;
s3c2440_i2c_xfer_data.cur_ptr = 0;
s3c2440_i2c_xfer_data.state = STATE_START;
/* 发出START信号和发出设备地址 */
s3c2440_i2c_start();
break;
}
else
{
/* 是最后一个消息的最后一个数据 */
s3c2440_i2c_stop(0);
break;
}
break;
}
case STATE_READ:
{
PRINTK("STATE_READn");
/* 读出数据 */
s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr] = s3c2440_i2c_regs->iicds;
s3c2440_i2c_xfer_data.cur_ptr ;
next_read:
if (!isEndData()) /* 如果数据没读写, 继续发起读操作 */
{
if (isLastData()) /* 如果即将读的数据是最后一个, 不发ack */
{
s3c2440_i2c_regs->iiccon = 0x2f; // 恢复I2C传输，接收到下一数据时无ACK
}
else
{
s3c2440_i2c_regs->iiccon = 0xaf; // 恢复I2C传输，接收到下一数据时发出ACK
}
break;
}
else if (!isLastMsg())
{
/* 开始处理下一个消息 */
s3c2440_i2c_xfer_data.msgs ;
s3c2440_i2c_xfer_data.cur_msg ;
s3c2440_i2c_xfer_data.cur_ptr = 0;
s3c2440_i2c_xfer_data.state = STATE_START;
/* 发出START信号和发出设备地址 */
s3c2440_i2c_start();
break;
}
else
{
/* 是最后一个消息的最后一个数据 */
s3c2440_i2c_stop(0);
break;
}
break;
}
default: break;
}
/* 清中断 */
s3c2440_i2c_regs->iiccon &= ~(S3C2410_IICCON_IRQPEND);
return IRQ_HANDLED;
}
/*
* I2C初始化
*/
static void s3c2440_i2c_init(void)
{
struct clk *clk;
clk = clk_get(NULL, "i2c");
clk_enable(clk);
// 选择引脚功能：GPE15:IICSDA, GPE14:IICSCL
s3c_gpio_cfgpin(S3C2410_GPE(14), S3C2410_GPE14_IICSCL);
s3c_gpio_cfgpin(S3C2410_GPE(15), S3C2410_GPE15_IICSDA);
/* bit[7] = 1, 使能ACK
* bit[6] = 0, IICCLK = PCLK/16
* bit[5] = 1, 使能中断
* bit[3:0] = 0xf, Tx clock = IICCLK/16
* PCLK = 50MHz, IICCLK = 3.125MHz, Tx Clock = 0.195MHz
*/
s3c2440_i2c_regs->iiccon = (1<<7) | (0<<6) | (1<<5) | (0xf); // 0xaf
s3c2440_i2c_regs->iicadd = 0x10; // S3C24xx slave address = [7:1]
s3c2440_i2c_regs->iicstat = 0x10; // I2C串行输出使能(Rx/Tx)
}
static int i2c_bus_s3c2440_init(void)
{
/* 2. 硬件相关的设置 */
s3c2440_i2c_regs = ioremap(0x54000000, sizeof(struct s3c2440_i2c_regs));
s3c2440_i2c_init();
request_irq(IRQ_IIC, s3c2440_i2c_xfer_irq, 0, "s3c2440-i2c", NULL);
init_waitqueue_head(&s3c2440_i2c_xfer_data.wait);
/* 3. 注册i2c_adapter */
i2c_add_adapter(&s3c2440_i2c_adapter);
return 0;
}
static void i2c_bus_s3c2440_exit(void)
{
i2c_del_adapter(&s3c2440_i2c_adapter);
free_irq(IRQ_IIC, NULL);
iounmap(s3c2440_i2c_regs);
}
module_init(i2c_bus_s3c2440_init);
module_exit(i2c_bus_s3c2440_exit);
MODULE_LICENSE("GPL");
make uImage 编译内核，加载新内核后重新启动。 装载驱动成功
读写测试
