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,//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//platform_device s3c_device_i2c0 >相互匹配成功后调用s3c24xx_i2c_probestatic 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 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 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 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 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*///最终的最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) 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;}
