I2C總線驅(qū)動(dòng)程序

#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

#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;

int cur_msg;

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) // 讀 //

{

s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->addr << 1;

s3c2440_i2c_regs->iicstat = 0xb0; // 主機(jī)接收，啟動(dòng)

}

else // 寫(xiě) //

{

s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->addr << 1;

s3c2440_i2c_regs->iicstat = 0xf0; // 主機(jī)發(fā)送，啟動(dòng)

}

}

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) // 讀 //

{

// 下面兩行恢復(fù)I2C操作，發(fā)出P信號(hào)

s3c2440_i2c_regs->iicstat = 0x90;

s3c2440_i2c_regs->iiccon = 0xaf;

ndelay(50); // 等待一段時(shí)間以便P信號(hào)已經(jīng)發(fā)出

}

else // 寫(xiě) //

{

// 下面兩行用來(lái)恢復(fù)I2C操作，發(fā)出P信號(hào)

s3c2440_i2c_regs->iicstat = 0xd0;

s3c2440_i2c_regs->iiccon = 0xaf;

ndelay(50); // 等待一段時(shí)間以便P信號(hào)已經(jīng)發(fā)出

}

// 喚醒 //

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個(gè)msg的I2C數(shù)據(jù)發(fā)送出去/讀進(jìn)來(lái) //

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/設(shè)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 : // 發(fā)出S和設(shè)備地址后,產(chǎn)生中斷 //

{

PRINTK("Startn");

// 如果沒(méi)有ACK, 返回錯(cuò)誤 //

if (iicSt & S3C2410_IICSTAT_LASTBIT)

{

s3c2440_i2c_stop(-ENODEV);

break;

}

if (isLastMsg() && isEndData())

{

s3c2440_i2c_stop(0);

break;

}

// 進(jìn)入下一個(gè)狀態(tài) //

if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) // 讀 //

{

s3c2440_i2c_xfer_data.state = STATE_READ;

goto next_read;

}

else

{

s3c2440_i2c_xfer_data.state = STATE_WRITE;

}

}

case STATE_WRITE:

{

PRINTK("STATE_WRITEn");

// 如果沒(méi)有ACK, 返回錯(cuò)誤 //

if (iicSt & S3C2410_IICSTAT_LASTBIT)

{

s3c2440_i2c_stop(-ENODEV);

break;

}

if (!isEndData()) // 如果當(dāng)前msg還有數(shù)據(jù)要發(fā)送 //

{

s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr];

s3c2440_i2c_xfer_data.cur_ptr++;

// 將數(shù)據(jù)寫(xiě)入IICDS后，需要一段時(shí)間才能出現(xiàn)在SDA線上

ndelay(50);

s3c2440_i2c_regs->iiccon = 0xaf; // 恢復(fù)I2C傳輸

break;

}

else if (!isLastMsg())

{

// 開(kāi)始處理下一個(gè)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;

// 發(fā)出START信號(hào)和發(fā)出設(shè)備地址 //

s3c2440_i2c_start();

break;

}

else

{

// 是最后一個(gè)消息的最后一個(gè)數(shù)據(jù) //

s3c2440_i2c_stop(0);

break;

}

break;

}

case STATE_READ:

{

PRINTK("STATE_READn");

// 讀出數(shù)據(jù) //

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()) // 如果數(shù)據(jù)沒(méi)讀完, 繼續(xù)發(fā)起讀操作 //

{

if (isLastData()) // 如果即將讀的數(shù)據(jù)是最后一個(gè), 不發(fā)ack //

{

s3c2440_i2c_regs->iiccon = 0x2f; // 恢復(fù)I2C傳輸，接收到下一數(shù)據(jù)時(shí)無(wú)ACK

}

else

{

s3c2440_i2c_regs->iiccon = 0xaf; // 恢復(fù)I2C傳輸，接收到下一數(shù)據(jù)時(shí)發(fā)出ACK

}

break;

}

else if (!isLastMsg())

{

// 開(kāi)始處理下一個(gè)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;

// 發(fā)出START信號(hào)和發(fā)出設(shè)備地址 //

s3c2440_i2c_start();

break;

}

else

{

// 是最后一個(gè)消息的最后一個(gè)數(shù)據(jù) //

s3c2440_i2c_stop(0);

break;

}

break;

}

default: break;

}

// 清中斷 //

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);

// 選擇引腳功能：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, 使能中斷

* 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串行輸出使能(Rx/Tx)

}

static int i2c_bus_s3c2440_init(void)

{

// 2. 硬件相關(guān)的設(shè)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. 注冊(cè)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");

==============================================================

解析：

應(yīng)用程序發(fā)送消息出去時(shí)，會(huì)調(diào)用適配器adapter里面的算法函數(shù)algo里面的master_xfer函數(shù)，先把消息記錄下來(lái)之后調(diào)用start函數(shù)，start函數(shù)里發(fā)送start啟動(dòng)信號(hào)并且把設(shè)備地址發(fā)送出去，然后休眠。發(fā)送完之后產(chǎn)生一個(gè)中斷，在中斷函數(shù)里面讀出狀態(tài)，如果沒(méi)有ack的話認(rèn)為發(fā)生錯(cuò)誤發(fā)出停止信號(hào)喚醒應(yīng)用程序；如果有ack信號(hào)而且是最后一個(gè)消息，最后一個(gè)數(shù)據(jù)則發(fā)出停止信號(hào)，否則進(jìn)入下一個(gè)狀態(tài)讀/寫(xiě)，如果是寫(xiě)判斷是否是最后一個(gè)數(shù)據(jù)，若還有數(shù)據(jù)要發(fā)送把數(shù)據(jù)發(fā)送出去，若是最后一個(gè)數(shù)據(jù)但是不是最后一個(gè)消息的話開(kāi)始處理下一個(gè)消息，發(fā)出start信號(hào)和設(shè)備地址，若是最后一個(gè)消息的最后一個(gè)數(shù)據(jù)則發(fā)出停止信號(hào)；如果是讀判斷數(shù)據(jù)是否讀完，如果沒(méi)有讀完但是接收到的不是最后一個(gè)數(shù)據(jù)則發(fā)送ack信號(hào)，若接收到最后一個(gè)數(shù)據(jù)否則無(wú)ack，但若數(shù)據(jù)已經(jīng)讀完則處理下一個(gè)消息發(fā)送start信號(hào)。