#include <linux/kernel.h> #include <linux/module.h> #include <linux/i2c.h> #include <linux/i2c-id.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/clk.h> #include <linux/cpufreq.h> #include <asm/irq.h> #include <asm/io.h> #include <plat/regs-iic.h> #include <plat/iic.h> /* i2c controller state */ //i2c控制器状态 enum s3c24xx_i2c_state { STATE_IDLE, STATE_START, STATE_READ, STATE_WRITE, STATE_STOP }; struct s3c24xx_i2c { spinlock_t lock; /* 在数据发送函数s3c24xx_i2c_doxfer中wait_event_timeout， 在数据发送完成函数s3c24xx_i2c_master_complete中wake_up */ wait_queue_head_t wait; unsigned int suspended:1; struct i2c_msg *msg;//管理收发数据的结构体 unsigned int msg_num;//待收发msg的数目 unsigned int msg_idx;//当前正在处理的msg在msg_num个msg中的序号 //每个msg都管理一段内存，msg_ptr是这段内存空间的偏移。 unsigned int msg_ptr; //在数据写入IICDS后的等待时间，在数据写入前SCL保持低电平，写入后 //释放，这个状态的建立需要一定的时间。 unsigned int tx_setup; unsigned int irq; enum s3c24xx_i2c_state state; //保存上一次通过clk_get_rate(i2c->clk);获取的频率。 //当本次获取的频率与clkrate不等时说明系统时钟改变。 unsigned long clkrate; void __iomem *regs; struct clk *clk; struct device *dev; struct resource *ioarea;// struct i2c_adapter adap;//适配器结构体，这整个结构体都是对它的包装。 #ifdef CONFIG_CPU_FREQ struct notifier_block freq_transition;//通知链 #endif }; /* default platform data removed, dev should always carry data. */ /* s3c24xx_i2c_is2440() * * return true is this is an s3c2440 */ //如果是s3c2440则返回1 static inline int s3c24xx_i2c_is2440(struct s3c24xx_i2c *i2c) { struct platform_device *pdev = to_platform_device(i2c->dev); return !strcmp(pdev->name, "s3c2440-i2c"); } /* s3c24xx_i2c_master_complete * * complete the message and wake up the caller, using the given return code, * or zero to mean ok. */ static inline void s3c24xx_i2c_master_complete(struct s3c24xx_i2c *i2c, int ret) { dev_dbg(i2c->dev, "master_complete %d\n", ret); i2c->msg_ptr = 0; i2c->msg = NULL; i2c->msg_idx++; i2c->msg_num = 0; if (ret) i2c->msg_idx = ret; //msg_num个msg都处理完则唤醒等待队列 wake_up(&i2c->wait); } //应答禁能 static inline void s3c24xx_i2c_disable_ack(struct s3c24xx_i2c *i2c) { unsigned long tmp; tmp = readl(i2c->regs + S3C2410_IICCON); writel(tmp & ~S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON); } //应答使能 static inline void s3c24xx_i2c_enable_ack(struct s3c24xx_i2c *i2c) { unsigned long tmp; tmp = readl(i2c->regs + S3C2410_IICCON); writel(tmp | S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON); } /* irq enable/disable functions */ //中断禁止 static inline void s3c24xx_i2c_disable_irq(struct s3c24xx_i2c *i2c) { unsigned long tmp; tmp = readl(i2c->regs + S3C2410_IICCON); writel(tmp & ~S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON); } //中断使能 static inline void s3c24xx_i2c_enable_irq(struct s3c24xx_i2c *i2c) { unsigned long tmp; tmp = readl(i2c->regs + S3C2410_IICCON); writel(tmp | S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON); } /* s3c24xx_i2c_message_start * * put the start of a message onto the bus */ //写入从器件地址，并发送起始信号 static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c, struct i2c_msg *msg) { unsigned int addr = (msg->addr & 0x7f) << 1;//最低位为读写标志 unsigned long stat; unsigned long iiccon; stat = 0; stat |= S3C2410_IICSTAT_TXRXEN;//数据收发使能 if (msg->flags & I2C_M_RD) { stat |= S3C2410_IICSTAT_MASTER_RX; addr |= 1;//主机读 } else stat |= S3C2410_IICSTAT_MASTER_TX;//主机写 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);//延时等待SCL被释放 dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon); writel(iiccon, i2c->regs + S3C2410_IICCON); stat |= S3C2410_IICSTAT_START; writel(stat, i2c->regs + S3C2410_IICSTAT);//发送起始信号 } static inline void s3c24xx_i2c_stop(struct s3c24xx_i2c *i2c, int ret) { unsigned long iicstat = readl(i2c->regs + S3C2410_IICSTAT); dev_dbg(i2c->dev, "STOP\n"); /* stop the transfer */ iicstat &= ~S3C2410_IICSTAT_START; writel(iicstat, i2c->regs + S3C2410_IICSTAT); i2c->state = STATE_STOP; //数据发送结束，唤醒等待队列 s3c24xx_i2c_master_complete(i2c, ret); s3c24xx_i2c_disable_irq(i2c); } /* helper functions to determine the current state in the set of * messages we are sending */ /* is_lastmsg() * * returns TRUE if the current message is the last in the set */ //msg_idx为当前msg在msg_num个发送msg中的偏移， static inline int is_lastmsg(struct s3c24xx_i2c *i2c) { return i2c->msg_idx >= (i2c->msg_num - 1); } /* is_msglast * * returns TRUE if we this is the last byte in the current message */ //msg_ptr为在msg中的len个数据中的偏移 static inline int is_msglast(struct s3c24xx_i2c *i2c) { return i2c->msg_ptr == i2c->msg->len-1; } /* is_msgend * * returns TRUE if we reached the end of the current message */ //当前msg中的数据处理完 static inline int is_msgend(struct s3c24xx_i2c *i2c) { return i2c->msg_ptr >= i2c->msg->len; } /* i2s_s3c_irq_nextbyte * * process an interrupt and work out what to do */ static int i2s_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat) { unsigned long tmp; unsigned char byte; int ret = 0; switch (i2c->state) { case STATE_IDLE: dev_err(i2c->dev, "%s: called in STATE_IDLE\n", __func__); goto out; break; case STATE_STOP: dev_err(i2c->dev, "%s: called in STATE_STOP\n", __func__); s3c24xx_i2c_disable_irq(i2c); goto out_ack;//如果当前为停止状态则清除中断挂起条件 case STATE_START://开始状态在开始数据传输函数s3c24xx_i2c_doxfer中设置 /* last thing we did was send a start condition on the * bus, or started a new i2c message */ if (iicstat & S3C2410_IICSTAT_LASTBIT && !(i2c->msg->flags & I2C_M_IGNORE_NAK)) { /* ack was not received... */ //没有收到应答信号则停止数据传输 dev_dbg(i2c->dev, "ack was not received\n"); s3c24xx_i2c_stop(i2c, -ENXIO); goto out_ack; } //其实信号成功发送后决定接下来要做的事情 if (i2c->msg->flags & I2C_M_RD) i2c->state = STATE_READ; else i2c->state = STATE_WRITE; /* terminate the transfer if there is nothing to do * as this is used by the i2c probe to find devices. */ //如果当前msg是队列中的最后一个而且没有要发送的数据则停止 if (is_lastmsg(i2c) && i2c->msg->len == 0) { s3c24xx_i2c_stop(i2c, 0); goto out_ack; } //当前中断是起始信号成功发送，下一次中断则是进行数据接收， //为接收数据准备可用的缓存 if (i2c->state == STATE_READ) goto prepare_read; /* fall through to the write state, as we will need to * send a byte as well */ case STATE_WRITE: /* we are writing data to the device... check for the * end of the message, and if so, work out what to do */ if (!(i2c->msg->flags & I2C_M_IGNORE_NAK)) { if (iicstat & S3C2410_IICSTAT_LASTBIT) { dev_dbg(i2c->dev, "WRITE: No Ack\n"); s3c24xx_i2c_stop(i2c, -ECONNREFUSED); goto out_ack; } } retry_write: if (!is_msgend(i2c)) { byte = i2c->msg->buf[i2c->msg_ptr++]; //i2c->msg_ptr++表明它总是指向第一个未被发送的数据 writeb(byte, i2c->regs + S3C2410_IICDS); //如果当前msg缓存中的数据没有全部发送则继续发送 /* delay after writing the byte to allow the * data setup time on the bus, as writing the * data to the register causes the first bit * to appear on SDA, and SCL will change as * soon as the interrupt is acknowledged */ ndelay(i2c->tx_setup); } else if (!is_lastmsg(i2c)) { /* we need to go to the next i2c message */ //如果当前msg中的数据发送完，而且msg不是msg队列中的最后一个 //则转向下一个待发送的msg dev_dbg(i2c->dev, "WRITE: Next Message\n"); i2c->msg_ptr = 0; i2c->msg_idx++; i2c->msg++; /* check to see if we need to do another message */ if (i2c->msg->flags & I2C_M_NOSTART) { if (i2c->msg->flags & I2C_M_RD) { /* cannot do this, the controller * forces us to send a new START * when we change direction */ //如果这一个msg处理的不是写而是读，数据传输方向变化了，则发送停止信号， //这个停止信号时异常停止，将导致数据的再次发送，即改变数据方向进行读取操作。 //在函数s3c24xx_i2c_xfer中可以看出，adap->retries决定了数据发送不成功 //可再次发送的次数。 s3c24xx_i2c_stop(i2c, -EINVAL); } //I2C_M_NOSTART如果是连续写则retry_write goto retry_write; } else { /* send the new start */ //如果数据不是连续写则每次写操作都要发送起始信号，写地址从器件地址。 s3c24xx_i2c_message_start(i2c, i2c->msg); i2c->state = STATE_START; } } else { /* send stop */ //如果当前msg中的数据发送完而且是msg队列中的最后一个msg则停止 s3c24xx_i2c_stop(i2c, 0); } break; case STATE_READ: /* we have a byte of data in the data register, do * something with it, and then work out wether we are * going to do any more read/write */ byte = readb(i2c->regs + S3C2410_IICDS); i2c->msg->buf[i2c->msg_ptr++] = byte; //i2c->msg_ptr++表明它总是指向缓存空间的下一个空的位置 prepare_read://每次数据读取都要为下一次读取做准备 if (is_msglast(i2c)) { /* last byte of buffer */ //如果当前msg只剩下最后一个字节空间，则还可以进行一次数据读取， //如果当前msg是msg队列中最后一个，则整个数据操作还能进行最后一次， //在这最后一次读取数据后不再发送应答信号。 if (is_lastmsg(i2c)) s3c24xx_i2c_disable_ack(i2c); } else if (is_msgend(i2c)) { /* ok, we've read the entire buffer, see if there * is anything else we need to do */ if (is_lastmsg(i2c)) { /* last message, send stop and complete */ dev_dbg(i2c->dev, "READ: Send Stop\n"); //如果当前msg中的缓存已用完，而且当前msg是msg队列中的最后一个则stop s3c24xx_i2c_stop(i2c, 0); } else { /* go to the next transfer */ dev_dbg(i2c->dev, "READ: Next Transfer\n"); //如果当前msg的缓存已耗尽，但msg不是msg队列的最后一个则转向下一个 i2c->msg_ptr = 0; i2c->msg_idx++; i2c->msg++; } } break; } /* acknowlegde the IRQ and get back on with the work */ out_ack: tmp = readl(i2c->regs + S3C2410_IICCON); tmp &= ~S3C2410_IICCON_IRQPEND; writel(tmp, i2c->regs + S3C2410_IICCON);//清除中断挂起条件 out: return ret; } /* s3c24xx_i2c_irq * * top level IRQ servicing routine */ //中断处理函数，从这个中断处理函数可以看出这个适配器不能工作在从机模式 static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id) { 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);//清除中断挂起条件 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);//up out: return IRQ_HANDLED; } /* s3c24xx_i2c_set_master * * get the i2c bus for a master transaction */ static int s3c24xx_i2c_set_master(struct s3c24xx_i2c *i2c) { unsigned long iicstat; int timeout = 400; while (timeout-- > 0) { iicstat = readl(i2c->regs + S3C2410_IICSTAT); if (!(iicstat & S3C2410_IICSTAT_BUSBUSY)) return 0; //等待SCL被释放，只有在此种状态下才可以设自己为主机状态 msleep(1); } return -ETIMEDOUT; } /* s3c24xx_i2c_doxfer * * this starts an i2c transfer */ //开始数据传输，函数，用户空间开始数据传输最终调用本函数 static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c, struct i2c_msg *msgs, int num) { unsigned long timeout; int ret; //在函数s3c24xx_i2c_probe中是用kzalloc分配的i2c的内存空间 //初始状态下i2c->suspended是为0的。不知道这样理解是否正确？ if (i2c->suspended)//如果处于挂起状态则不能进行数据传输 return -EIO; ret = s3c24xx_i2c_set_master(i2c);//等待总线空闲 if (ret != 0) { dev_err(i2c->dev, "cannot get bus (error %d)\n", ret); ret = -EAGAIN; goto out; } spin_lock_irq(&i2c->lock); //获取待处理的msg队列 i2c->msg = msgs; i2c->msg_num = num; i2c->msg_ptr = 0; i2c->msg_idx = 0; i2c->state = STATE_START;//开始数据处理 s3c24xx_i2c_enable_irq(i2c); s3c24xx_i2c_message_start(i2c, msgs);//发送起始信号和设备地址 spin_unlock_irq(&i2c->lock); //超时等待数据处理结束，这段时间内进程将处于睡眠状态 timeout = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5); //如果数据处理异常结束，它将返回错误标识。s3c24xx_i2c_stop 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 */ //确保停止信号已成功发送 msleep(1); out: return ret; } /* s3c24xx_i2c_xfer * * first port of call from the i2c bus code when an message needs * transferring across the i2c bus. */ //对函数s3c24xx_i2c_doxfer的包装 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); //如果数据发送不成功可再次发送。 //比如在msg队列中有些是读取操作有些是数据写操作。 if (ret != -EAGAIN) return ret; dev_dbg(i2c->dev, "Retrying transmission (%d)\n", retry); udelay(100); } return -EREMOTEIO; } /* declare our i2c functionality */ static u32 s3c24xx_i2c_func(struct i2c_adapter *adap) {//申明i2c支持的功能 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING; } /* i2c bus registration info */ //i2c_algorithm适配器的操作函数 static const struct i2c_algorithm s3c24xx_i2c_algorithm = { .master_xfer = s3c24xx_i2c_xfer, .functionality = s3c24xx_i2c_func, }; /* s3c24xx_i2c_calcdivisor * * return the divisor settings for a given frequency */ //IIC能进行两处分频，一处是16倍和512倍，另一处是0~16分频 //clkin存放IICCLK，wanted为想要设置的频率。 //经计算后div1放第一处分频值16或512，divs放第二处分频值， //函数的返回值是经分频后实际的频率值 static int s3c24xx_i2c_calcdivisor(unsigned long clkin, unsigned int wanted, unsigned int *div1, unsigned int *divs) { unsigned int calc_divs = clkin / wanted; unsigned int calc_div1; if (calc_divs > (16*16)) calc_div1 = 512; else calc_div1 = 16; calc_divs += calc_div1-1; calc_divs /= calc_div1; if (calc_divs == 0) calc_divs = 1; if (calc_divs > 17) calc_divs = 17; *divs = calc_divs; *div1 = calc_div1; return clkin / (calc_divs * calc_div1); } /* s3c24xx_i2c_clockrate * * work out a divisor for the user requested frequency setting, * either by the requested frequency, or scanning the acceptable * range of frequencies until something is found */ static int s3c24xx_i2c_clockrate(struct s3c24xx_i2c *i2c, unsigned int *got) { struct s3c2410_platform_i2c *pdata = i2c->dev->platform_data; unsigned long clkin = clk_get_rate(i2c->clk); unsigned int divs, div1; unsigned long target_frequency; u32 iiccon; int freq; i2c->clkrate = clkin;// 存放IICCLK clkin /= 1000; /* clkin now in KHz */ dev_dbg(i2c->dev, "pdata desired frequency %lu\n", pdata->frequency); //pdata->frequency在移植时可在文件dev-i2c.c中设置 target_frequency = pdata->frequency ? pdata->frequency : 100000; // target_frequency /= 1000; /* Target frequency now in KHz */ //根据IICCLK（clkin）和想要设置的频率（target_frequency），计算出 //第一次分频和第二次分频的值，返回实际得到的频率值 freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs); if (freq > target_frequency) { dev_err(i2c->dev, "Unable to achieve desired frequency %luKHz." \ " Lowest achievable %dKHz\n", target_frequency, freq); return -EINVAL; } *got = freq; iiccon = readl(i2c->regs + S3C2410_IICCON); iiccon &= ~(S3C2410_IICCON_SCALEMASK | S3C2410_IICCON_TXDIV_512); iiccon |= (divs-1); if (div1 == 512) iiccon |= S3C2410_IICCON_TXDIV_512; //写入分频值 writel(iiccon, i2c->regs + S3C2410_IICCON); if (s3c24xx_i2c_is2440(i2c)) { unsigned long sda_delay; if (pdata->sda_delay) { sda_delay = (freq / 1000) * pdata->sda_delay; sda_delay /= 1000000; sda_delay = DIV_ROUND_UP(sda_delay, 5); if (sda_delay > 3) sda_delay = 3;//不是很明白SDA线路延时长度选择是什么意思 sda_delay |= S3C2410_IICLC_FILTER_ON; } else sda_delay = 0; dev_dbg(i2c->dev, "IICLC=%08lx\n", sda_delay); writel(sda_delay, i2c->regs + S3C2440_IICLC); } return 0; } #ifdef CONFIG_CPU_FREQ #define freq_to_i2c(_n) container_of(_n, struct s3c24xx_i2c, freq_transition) //通知链中事件发生时的回调函数 static int s3c24xx_i2c_cpufreq_transition(struct notifier_block *nb, unsigned long val, void *data) { struct s3c24xx_i2c *i2c = freq_to_i2c(nb); unsigned long flags; unsigned int got; int delta_f; int ret; delta_f = clk_get_rate(i2c->clk) - i2c->clkrate; /* if we're post-change and the input clock has slowed down * or at pre-change and the clock is about to speed up, then * adjust our clock rate. <0 is slow, >0 speedup. */ if ((val == CPUFREQ_POSTCHANGE && delta_f < 0) || (val == CPUFREQ_PRECHANGE && delta_f > 0)) { spin_lock_irqsave(&i2c->lock, flags); ret = s3c24xx_i2c_clockrate(i2c, &got);//重新计算并设置频率 spin_unlock_irqrestore(&i2c->lock, flags); if (ret < 0) dev_err(i2c->dev, "cannot find frequency\n"); else dev_info(i2c->dev, "setting freq %d\n", got); } return 0; } //将节点i2c->freq_transition加入通知链 static inline int s3c24xx_i2c_register_cpufreq(struct s3c24xx_i2c *i2c) { i2c->freq_transition.notifier_call = s3c24xx_i2c_cpufreq_transition; return cpufreq_register_notifier(&i2c->freq_transition, CPUFREQ_TRANSITION_NOTIFIER); } static inline void s3c24xx_i2c_deregister_cpufreq(struct s3c24xx_i2c *i2c) { cpufreq_unregister_notifier(&i2c->freq_transition, CPUFREQ_TRANSITION_NOTIFIER); } #else static inline int s3c24xx_i2c_register_cpufreq(struct s3c24xx_i2c *i2c) { return 0; } static inline void s3c24xx_i2c_deregister_cpufreq(struct s3c24xx_i2c *i2c) { } #endif /* s3c24xx_i2c_init * * initialise the controller, set the IO lines and frequency */ static int s3c24xx_i2c_init(struct s3c24xx_i2c *i2c) { unsigned long iicon = S3C2410_IICCON_IRQEN | S3C2410_IICCON_ACKEN; struct s3c2410_platform_i2c *pdata; unsigned int freq; /* get the plafrom data */ pdata = i2c->dev->platform_data; /* inititalise the gpio */ if (pdata->cfg_gpio) pdata->cfg_gpio(to_platform_device(i2c->dev)); /* write slave address */ //写入本机的从器件地址 writeb(pdata->slave_addr, i2c->regs + S3C2410_IICADD); dev_info(i2c->dev, "slave address 0x%02x\n", pdata->slave_addr); writel(iicon, i2c->regs + S3C2410_IICCON); /* we need to work out the divisors for the clock... */ //设置频率 if (s3c24xx_i2c_clockrate(i2c, &freq) != 0) { writel(0, i2c->regs + S3C2410_IICCON); dev_err(i2c->dev, "cannot meet bus frequency required\n"); return -EINVAL; } /* todo - check that the i2c lines aren't being dragged anywhere */ dev_info(i2c->dev, "bus frequency set to %d KHz\n", freq); dev_dbg(i2c->dev, "S3C2410_IICCON=0x%02lx\n", iicon); /* check for s3c2440 i2c controller */ if (s3c24xx_i2c_is2440(i2c))//如果是2440则。。。不太明白 writel(0x0, i2c->regs + S3C2440_IICLC); return 0; } /* s3c24xx_i2c_probe * * called by the bus driver when a suitable device is found */ static int s3c24xx_i2c_probe(struct platform_device *pdev) { struct s3c24xx_i2c *i2c; struct s3c2410_platform_i2c *pdata; struct resource *res; int ret; //这个私有成员是器件移植的关键 pdata = pdev->dev.platform_data; if (!pdata) { dev_err(&pdev->dev, "no platform data\n"); return -EINVAL; } //为结构体i2c分配内存空间并清零。 i2c = kzalloc(sizeof(struct s3c24xx_i2c), GFP_KERNEL); if (!i2c) { dev_err(&pdev->dev, "no memory for state\n"); return -ENOMEM; } //这整个驱动程序就是在向内核加一个适配器。 strlcpy(i2c->adap.name, "s3c2410-i2c", sizeof(i2c->adap.name)); i2c->adap.owner = THIS_MODULE; i2c->adap.algo = &s3c24xx_i2c_algorithm;//适配器操作方法 i2c->adap.retries = 2;//数据传输异常打断后，重复尝试的次数 i2c->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD; i2c->tx_setup = 50;//数据写入IICDS后延时时间 spin_lock_init(&i2c->lock); init_waitqueue_head(&i2c->wait);//初始化等待队列头 /* find the clock and enable it */ i2c->dev = &pdev->dev; i2c->clk = clk_get(&pdev->dev, "i2c");//获取平台时钟 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);//使能时钟 /* map the registers */ //获取I/O资源 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; } //申请IO内存 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; } //IO映射 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 */ //将i2c结构体设为adap的私有数据成员 i2c->adap.algo_data = i2c; i2c->adap.dev.parent = &pdev->dev; /* initialise the i2c controller */ ret = s3c24xx_i2c_init(i2c);//如上 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 */ i2c->irq = ret = platform_get_irq(pdev, 0); if (ret <= 0) { dev_err(&pdev->dev, "cannot find IRQ\n"); goto err_iomap; } //申请一个中断并关联它的处理函数，IRQF_DISABLED该中断不被共享（我认为） 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; } //将通知节点注册到通知链。 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. */ i2c->adap.nr = pdata->bus_num;//设置总线号 //添加一个适配器设备 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; } //将i2c设为pdev的drvdata。 platform_set_drvdata(pdev, i2c); dev_info(&pdev->dev, "%s: S3C I2C adapter\n", dev_name(&i2c->adap.dev)); 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; } /* s3c24xx_i2c_remove * * called when device is removed from the bus */ static int s3c24xx_i2c_remove(struct platform_device *pdev) { struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev); s3c24xx_i2c_deregister_cpufreq(i2c); i2c_del_adapter(&i2c->adap); free_irq(i2c->irq, i2c); clk_disable(i2c->clk); clk_put(i2c->clk); iounmap(i2c->regs); release_resource(i2c->ioarea); kfree(i2c->ioarea); kfree(i2c); return 0; } #ifdef CONFIG_PM static int s3c24xx_i2c_suspend_late(struct platform_device *dev, pm_message_t msg) { struct s3c24xx_i2c *i2c = platform_get_drvdata(dev); i2c->suspended = 1; return 0; } static int s3c24xx_i2c_resume(struct platform_device *dev) { struct s3c24xx_i2c *i2c = platform_get_drvdata(dev); i2c->suspended = 0; s3c24xx_i2c_init(i2c); return 0; } #else #define s3c24xx_i2c_suspend_late NULL #define s3c24xx_i2c_resume NULL #endif /* device driver for platform bus bits */ static struct platform_driver s3c2410_i2c_driver = { .probe = s3c24xx_i2c_probe, .remove = s3c24xx_i2c_remove, .suspend_late = s3c24xx_i2c_suspend_late, .resume = s3c24xx_i2c_resume, .driver = { .owner = THIS_MODULE, .name = "s3c2410-i2c", }, }; static struct platform_driver s3c2440_i2c_driver = { .probe = s3c24xx_i2c_probe, .remove = s3c24xx_i2c_remove, .suspend_late = s3c24xx_i2c_suspend_late, .resume = s3c24xx_i2c_resume, .driver = { .owner = THIS_MODULE, .name = "s3c2440-i2c", }, }; 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; } subsys_initcall(i2c_adap_s3c_init); static void __exit i2c_adap_s3c_exit(void) { platform_driver_unregister(&s3c2410_i2c_driver); platform_driver_unregister(&s3c2440_i2c_driver); } module_exit(i2c_adap_s3c_exit); MODULE_DESCRIPTION("S3C24XX I2C Bus driver"); MODULE_AUTHOR("Ben Dooks, <ben@simtec.co.uk>"); MODULE_LICENSE("GPL"); MODULE_ALIAS("platform:s3c2410-i2c"); MODULE_ALIAS("platform:s3c2440-i2c");
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