i2c-core.c这个文件实现了I2C核心的功能以及/proc/bus/i2c*接口。
i2c-dev.c实
现了I2C适配器设备文件的功能，每一个I2C适配器都被分配一个设备。通过适配器访设备时的主设备号都为89，次设备号为0-255。I2c-
dev.c并没有针对特定的设备而设计，只是提供了通用的read(),write(),和ioctl()等接口，应用层可以借用这些接口访问挂接在适配
器上的I2C设备的存储空间或寄存器，并控制I2C设备的工作方式。
busses文件夹这个文件中包含了一些I2C总线的驱动，如针对S3C2410，S3C2440，S3C6410等处理器的I2C控制器驱动为i2c-s3c2410.c.
algos文件夹实现了一些I2C总线适配器的algorithm.
//////////////////////////////////////////////////////////////////////////////////
//描述6410芯片里I2C控制器
struct
s3c24xx_i2c {
spinlock_t lock;
wait_queue_head_t wait;
unsigned int suspended:1;
struct i2c_msg *msg;
unsigned int msg_num;
unsigned int msg_idx;
unsigned int msg_ptr;
unsigned int tx_setup;
unsigned int irq;
enum s3c24xx_i2c_state state;
unsigned long clkrate;
void __iomem *regs;
struct clk *clk;
struct device *dev;
struct resource *ioarea;
struct i2c_adapter adap;
#ifdef CONFIG_CPU_FREQ
struct notifier_block freq_transition;
#endif
};
///////////////////////////////////////////////////////////////////////////////////
module_init(
i2c_adap_s3c_init);
static int __init i2c_adap_s3c_init(void)
{
int ret;
ret = platform_driver_register(&s3c2410_i2c_driver);
if (ret == 0) {
ret = platform_driver_register(&s3c2440_i2c_driver);
if (ret)
platform_driver_unregister(&s3c2410_i2c_driver);
}
return ret;
}
///////////////////////////////////////////////////////////////////////////////////
/* device driver for platform bus bits */
static struct platform_driver s3c2410_i2c_driver = {
//Probe的规则是：如果BUS上实现了probe就用BUS的probe；否则才会用driver的probe
.probe =
s3c24xx_i2c_probe,
.remove = s3c24xx_i2c_remove,
.suspend_late = s3c24xx_i2c_suspend_late,
.resume = s3c24xx_i2c_resume,
.driver = {
.owner = THIS_MODULE,
//< struct
platform_device s3c_device_i2c0 >相互匹配
.name = "
s3c2410-i2c",
},
};
BUS
上实现的.match()函数，定义了Device和Driver绑定时的规则。比如Platform实现的就是先比较id_table，然后比较
name的规则。如果BUS的match()函数没实现，认为BUS上的所有的Device和Driver都是match的，具体后续过程要看
probe()的实现了
///////////////////////////////////////////////////////////////////////////////////
/* s3c24xx_i2c_probe
*
* called by the bus driver when a suitable device is found
*/
与//< struct
platform_device s3c_device_i2c0 >相互匹配成功后调用s3c24xx_i2c_probe
static int
s3c24xx_i2c_probe(struct platform_device *pdev)
{
struct s3c24xx_i2c *i2c;
struct s3c2410_platform_i2c *pdata;
struct resource *res;
int ret;
pdata = pdev->dev.platform_data;
if (!pdata) {
dev_err(&pdev->dev, "no platform data\n");
return -EINVAL;
}
i2c = kzalloc(sizeof(struct s3c24xx_i2c), GFP_KERNEL);
if (!i2c) {
dev_err(&pdev->dev, "no memory for state\n");
return -ENOMEM;
}
strlcpy(i2c->adap.name, "s3c2410-i2c", sizeof(i2c->adap.name));
i2c->adap.owner = THIS_MODULE;
//这里是用于传输读写的
i2c->adap.algo = &s3c24xx_i2c_algorithm;
i2c->adap.retries = 2;
i2c->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
i2c->tx_setup = 50;
spin_lock_init(&i2c->lock);
init_waitqueue_head(&i2c->wait);
/* find the clock and enable it */
i2c->dev = &pdev->dev;
i2c->clk = clk_get(&pdev->dev, "i2c");
if (IS_ERR(i2c->clk)) {
dev_err(&pdev->dev, "cannot get clock\n");
ret = -ENOENT;
goto err_noclk;
}
dev_dbg(&pdev->dev, "clock source %p\n", i2c->clk);
clk_enable(i2c->clk);
/* map the registers */
//获取i2c寄存器内存地址
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (res == NULL) {
dev_err(&pdev->dev, "cannot find IO resource\n");
ret = -ENOENT;
goto err_clk;
}
i2c->ioarea = request_mem_region(res->start, (res->end-res->start)+1,
pdev->name);
if (i2c->ioarea == NULL) {
dev_err(&pdev->dev, "cannot request IO\n");
ret = -ENXIO;
goto err_clk;
}
i2c->regs = ioremap(res->start, (res->end-res->start)+1);
if (i2c->regs == NULL) {
dev_err(&pdev->dev, "cannot map IO\n");
ret = -ENXIO;
goto err_ioarea;
}
dev_dbg(&pdev->dev, "registers %p (%p, %p)\n",
i2c->regs, i2c->ioarea, res);
/* setup info block for the i2c core */
i2c->adap.algo_data = i2c;
i2c->adap.dev.parent = &pdev->dev;
/* initialise the i2c controller */
ret = s3c24xx_i2c_init(i2c);
if (ret != 0)
goto err_iomap;
/* find the IRQ for this unit (note, this relies on the init call to
* ensure no current IRQs pending
*/
//获取i2c irq中断资源 在platform设备和驱动里定义的。
i2c->irq = ret = platform_get_irq(pdev, 0);
if (ret <= 0) {
dev_err(&pdev->dev, "cannot find IRQ\n");
goto err_iomap;
}
//申请i2c IRQ中断
ret = request_irq(i2c->irq, s3c24xx_i2c_irq, IRQF_DISABLED,
dev_name(&pdev->dev), i2c);
if (ret != 0) {
dev_err(&pdev->dev, "cannot claim IRQ %d\n", i2c->irq);
goto err_iomap;
}
ret = s3c24xx_i2c_register_cpufreq(i2c);
if (ret < 0) {
dev_err(&pdev->dev, "failed to register cpufreq notifier\n");
goto err_irq;
}
/* Note, previous versions of the driver used i2c_add_adapter()
* to add the bus at any number. We now pass the bus number via
* the platform data, so if unset it will now default to always
* being bus 0.
*/
//见
//
i2c_scan_static_board_info函数
// if (devinfo->busnum == adapter->nr && !i2c_new_device(adapter,&devinfo->board_info))
//只有如果adapter的号码和节点中的号码相同，才会调用
i2c_new_device创建i2c clien
i2c->adap.nr = pdata->bus_num;
//注册了struct i2c_adapter
//并且根据i2c_register_board_info()添加到链表里的板子信息注册 struct i2c_client
//
//执行完i2c_add_numbered_adapter函数后，内核的i2c总线上已有adapter device和client device
//在里
ret =
i2c_add_numbered_adapter(&
i2c->adap);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add bus to i2c core\n");
goto err_cpufreq;
}
platform_set_drvdata(pdev, i2c);
dev_info(&pdev->dev, "%s: S3C I2C adapter\n", i2c->adap.dev.bus_id);
return 0;
err_cpufreq:
s3c24xx_i2c_deregister_cpufreq(i2c);
err_irq:
free_irq(i2c->irq, i2c);
err_iomap:
iounmap(i2c->regs);
err_ioarea:
release_resource(i2c->ioarea);
kfree(i2c->ioarea);
err_clk:
clk_disable(i2c->clk);
clk_put(i2c->clk);
err_noclk:
kfree(i2c);
return ret;
}
/////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////
/* i2c bus registration info */
//用于读写传输的算法结构
static const struct i2c_algorithm
s3c24xx_i2c_algorithm = {
.master_xfer =
s3c24xx_i2c_xfer,
.functionality = s3c24xx_i2c_func,
};
/////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////
/* s3c24xx_i2c_xfer
*
* first port of call from the i2c bus code when an message needs
* transferring across the i2c bus.
*/
static int
s3c24xx_i2c_xfer(struct i2c_adapter *adap,
struct i2c_msg *msgs, int num)
{
struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;
int retry;
int ret;
for (retry = 0; retry < adap->retries; retry++) {
ret =
s3c24xx_i2c_doxfer(i2c, msgs, num);
if (ret != -EAGAIN)
return ret;
dev_dbg(i2c->dev, "Retrying transmission (%d)\n", retry);
udelay(100);
}
return -EREMOTEIO;
}
//////////////////////////////////////////////////////////////////////////////////
/* s3c24xx_i2c_doxfer
*
* this starts an i2c transfer
*/
static int
s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
struct i2c_msg *msgs, int num)
{
unsigned long timeout;
int ret;
if (i2c->suspended)
return -EIO;
ret = s3c24xx_i2c_set_master(i2c);
if (ret != 0) {
dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
ret = -EAGAIN;
goto out;
}
spin_lock_irq(&i2c->lock);
i2c->msg = msgs;
i2c->msg_num = num;
i2c->msg_ptr = 0;
i2c->msg_idx = 0;
i2c->state = STATE_START;
s3c24xx_i2c_enable_irq(i2c);
s3c24xx_i2c_message_start(i2c, msgs);
spin_unlock_irq(&i2c->lock);
timeout =
wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5);
ret = i2c->msg_idx;
/* having these next two as dev_err() makes life very
* noisy when doing an i2cdetect */
if (timeout == 0)
dev_dbg(i2c->dev, "timeout\n");
else if (ret != num)
dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);
/* ensure the stop has been through the bus */
msleep(1);
out:
return ret;
}
//////////////////////////////////////////////////////////////////////////////////
/* s3c24xx_i2c_message_start
*
* put the start of a message onto the bus
*/
//{BANNED}最佳终的{BANNED}最佳底层的读写函数在此
static void
s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c,
struct i2c_msg *msg)
{
unsigned int addr = (msg->addr & 0x7f) << 1;
unsigned long stat;
unsigned long iiccon;
stat = 0;
stat |= S3C2410_IICSTAT_TXRXEN;
if (msg->flags & I2C_M_RD) {
stat |= S3C2410_IICSTAT_MASTER_RX;
addr |= 1;
} else
stat |= S3C2410_IICSTAT_MASTER_TX;
if (msg->flags & I2C_M_REV_DIR_ADDR)
addr ^= 1;
/* todo - check for wether ack wanted or not */
s3c24xx_i2c_enable_ack(i2c);
iiccon = readl(i2c->regs + S3C2410_IICCON);
writel(stat, i2c->regs + S3C2410_IICSTAT);
dev_dbg(i2c->dev, "START: %08lx to IICSTAT, %02x to DS\n", stat, addr);
writeb(addr, i2c->regs + S3C2410_IICDS);
/* delay here to ensure the data byte has gotten onto the bus
* before the transaction is started */
ndelay(i2c->tx_setup);
dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
writel(iiccon, i2c->regs + S3C2410_IICCON);
stat |= S3C2410_IICSTAT_START;
writel(stat, i2c->regs + S3C2410_IICSTAT);
}
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////
/* s3c24xx_i2c_irq
*
* top level IRQ servicing routine
*/
//芯片手册s3c6410 iic一章。
//在i2c时序的ACK时会产生中断，ACK是在一个字节数据发送完时出现ACK。
static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id)
{
//dev_id这个参数是s3c24xx_i2c_probe函数里的 struct s3c24xx_i2c *i2c;这个类型的成员
struct s3c24xx_i2c *i2c = dev_id;
unsigned long status;
unsigned long tmp;
status = readl(i2c->regs + S3C2410_IICSTAT);
if (status & S3C2410_IICSTAT_ARBITR) {
/* deal with arbitration loss */
dev_err(i2c->dev, "deal with arbitration loss\n");
}
if (i2c->state == STATE_IDLE) {
dev_dbg(i2c->dev, "IRQ: error i2c->state == IDLE\n");
tmp = readl(i2c->regs + S3C2410_IICCON);
tmp &= ~S3C2410_IICCON_IRQPEND;
writel(tmp, i2c->regs + S3C2410_IICCON);
goto out;
}
/* pretty much this leaves us with the fact that we've
* transmitted or received whatever byte we last sent */
i2s_s3c_irq_nextbyte(i2c, status);
out:
return IRQ_HANDLED;
}
