6410触摸屏驱动分析（s3c-ts.c）（Linux）（分析）

/* linux/drivers/input/touchscreen/s3c-ts.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * a misc driver for mini6410 touch screen
 *  by FriendlyARM 2010
 *
 * Based on following software:
 *
 ** Copyright (c) 2004 Arnaud Patard <arnaud.patard@rtp-net.org>
 ** iPAQ H1940 touchscreen support
 **
 ** ChangeLog
 **
 ** 2004-09-05: Herbert Potzl <herbert@13thfloor.at>
 ** - added clock (de-)allocation code
 **
 ** 2005-03-06: Arnaud Patard <arnaud.patard@rtp-net.org>
 **      - h1940_ -> s3c24xx (this driver is now also used on the n30
 **        machines :P)
 **      - Debug messages are now enabled with the config option
 **        TOUCHSCREEN_S3C_DEBUG
 **      - Changed the way the value are read
 **      - Input subsystem should now work
 **      - Use ioremap and readl/writel
 **
 ** 2005-03-23: Arnaud Patard <arnaud.patard@rtp-net.org>
 **      - Make use of some undocumented features of the touchscreen
 **        controller
 **
 ** 2006-09-05: Ryu Euiyoul <ryu.real@gmail.com>
 **      - added power management suspend and resume code
 *
 */
 
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/serio.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
 
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <mach/hardware.h>
 
#include <plat/regs-adc.h>
#include <mach/irqs.h>
#include <mach/map.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>
#include <mach/gpio-bank-a.h>
#include <mach/ts.h>
 
#define CONFIG_TOUCHSCREEN_S3C_DEBUG
#undef CONFIG_TOUCHSCREEN_S3C_DEBUG
#define DEBUG_LVL       KERN_DEBUG
 
 
#ifdef CONFIG_MINI6410_ADC
DEFINE_SEMAPHORE(ADC_LOCK);  //定义并初始化了一个信号量
                          //37内核就没有DECLARE_MUTEX了吧，功能应该是一样的
 
 
/* Indicate who is using the ADC controller */
//ADC的状态，防止触摸屏转换时，ADC正在被使用
#define LOCK_FREE       0
#define LOCK_TS         1
#define LOCK_ADC        2
static int adc_lock_id = LOCK_FREE;
 
#define ADC_free()      (adc_lock_id == LOCK_FREE)  
#define ADC_locked4TS() (adc_lock_id == LOCK_TS)
 
//==
static inline int s3c_ts_adc_lock(int id) {
    int ret;
 
    ret = down_trylock(&ADC_LOCK); //获取自旋锁
    if (!ret) {
        adc_lock_id = id;
    }
 
    return ret;  //返回状态  1:失败  0：成功
}
//--
 
static inline void s3c_ts_adc_unlock(void) {
    adc_lock_id = 0;
    up(&ADC_LOCK);  //释放自旋锁
}
#endif
 
 
/* Touchscreen default configuration */
struct s3c_ts_mach_info s3c_ts_default_cfg __initdata = {
    .delay              = 10000,  //转换延时
    .presc              = 49,  //转换时钟分频
    .oversampling_shift = 2,      //转换次数  4次
    .resol_bit          = 12, //转换精度
    .s3c_adc_con        = ADC_TYPE_2   //6410是type2
};
/*
struct s3c_ts_mach_info s3c_ts_default_cfg __initdata = {
    .delay              = 10000,
    .presc              = 49,
    .oversampling_shift = 2,
    .resol_bit          = 10
};
*/
/*
 * Definitions & global arrays.
 */
#define DEVICE_NAME     "touchscreen"
static DECLARE_WAIT_QUEUE_HEAD(ts_waitq); //定义并初始化一个等待队列
 
typedef unsigned        TS_EVENT;
#define NR_EVENTS       64     //触摸屏fifo大小
 
static TS_EVENT         events[NR_EVENTS];
static int              evt_head, evt_tail; //fifo的头的尾
                                                            //驱动写fifo时evt_head++，应用读fifo时 evt_tail++
 
#define ts_evt_pending()    ((volatile u8)(evt_head != evt_tail))   //相等就表示满了
#define ts_evt_get()        (events + evt_tail)
#define ts_evt_pull()       (evt_tail = (evt_tail + 1) & (NR_EVENTS - 1))
#define ts_evt_clear()      (evt_head = evt_tail = 0)
 
//将AD转换的值放入FIFO
//这里是一个先进先出的fifo
//只要有数据被添加进来，就会唤醒ts_waitq进程
static void ts_evt_add(unsigned x, unsigned y, unsigned down) {
    unsigned ts_event;
    int next_head;
 
    ts_event = ((x << 16) | (y)) | (down << 31);
    next_head = (evt_head + 1) & (NR_EVENTS - 1);
        //没满就装入
    if (next_head != evt_tail) {
        events[evt_head] = ts_event;
        evt_head = next_head;
        //printk("====>Add ... [ %4d,  %4d ]%s\n", x, y, down ? "":" ~~~");
 
        /* wake up any read call */
        if (waitqueue_active(&ts_waitq)) { //判斷等待隊列是否有進程睡眠
            wake_up_interruptible(&ts_waitq);  //唤醒ts_waitq等待队列中所有interruptible类型的进程
        }
    } else {
        /* drop the event and try to wakeup readers */
        printk(KERN_WARNING "mini6410-ts: touch event buffer full");
        wake_up_interruptible(&ts_waitq);
    }
}
 
static unsigned int s3c_ts_poll( struct file *file, struct poll_table_struct *wait)
{
    unsigned int mask = 0;
 
    //将ts_waitq等待队列添加到poll_table里去
    poll_wait(file, &ts_waitq, wait); 
    //返回掩码                                  
    if (ts_evt_pending())
        mask |= POLLIN | POLLRDNORM;  //返回设备可读
 
    return mask;
}
 
//读 系统调用==
static int s3c_ts_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)
{
    DECLARE_WAITQUEUE(wait, current); //把当前进程加到定义的等待队列头wait中 
    char *ptr = buff;
    int err = 0;
 
    add_wait_queue(&ts_waitq, &wait); //把wait入到等待队列头中。该队列会在进程等待的条件满足时唤醒它。
                                      //我们必须在其他地方写相关代码，在事件发生时，对等的队列执行wake_up()操作。
                                      //这里是在ts_evt_add里wake_up
    while (count >= sizeof(TS_EVENT)) {
        err = -ERESTARTSYS;
        if (signal_pending(current)) //如果是信号唤醒    参考http://www.360doc.com/content/10/1009/17/1317564_59632874.shtml
            break;
 
        if (ts_evt_pending()) {
            TS_EVENT *evt = ts_evt_get();
 
            err = copy_to_user(ptr, evt, sizeof(TS_EVENT));
            ts_evt_pull();
 
            if (err)
                break;
 
            ptr += sizeof(TS_EVENT);
            count -= sizeof(TS_EVENT);
            continue;
        }
 
        set_current_state(TASK_INTERRUPTIBLE); //改变进程状态为可中断的睡眠
        err = -EAGAIN;
        if (filp->f_flags & O_NONBLOCK) //如果上层调用是非阻塞方式，则不阻塞该进程，直接返回EAGAIN
            break;
        schedule();  //本进程在此处交出CPU控制权，等待被唤醒
                      //进程调度的意思侧重于把当前任务从CPU拿掉，再从就绪队列中按照调度算法取一就绪进程占用CPU
    }
    current->state = TASK_RUNNING;
    remove_wait_queue(&ts_waitq, &wait);
 
    return ptr == buff ? err : ptr - buff;
}
//--
 
static int s3c_ts_open(struct inode *inode, struct file *filp) {
    /* flush event queue */
    ts_evt_clear();
 
    return 0;
}
 
//当应用程序操作设备文件时调用的open read等函数，最终会调用这个结构体中对应的函数
static struct file_operations dev_fops = {
    .owner              = THIS_MODULE,
    .read               = s3c_ts_read,
    .poll               = s3c_ts_poll,  //select系统调用
    .open               = s3c_ts_open,
};
 
//设备号，设备名，注册的时候用到这个数组
//混杂设备主设备号为10
static struct miscdevice misc = {
        .minor              = MISC_DYNAMIC_MINOR, //自动分配次设置号
    //.minor                = 180, 
    .name               = DEVICE_NAME,
    .fops               = &dev_fops,
};
 
//x为0时为等待按下中断，x为1是为等待抬起中断
#define WAIT4INT(x)     (((x) << 8) | \
        S3C_ADCTSC_YM_SEN | S3C_ADCTSC_YP_SEN | S3C_ADCTSC_XP_SEN | \
        S3C_ADCTSC_XY_PST(3))
 
//自动连续测量X坐标和Y坐标
#define AUTOPST         (S3C_ADCTSC_YM_SEN | S3C_ADCTSC_YP_SEN | S3C_ADCTSC_XP_SEN | \
        S3C_ADCTSC_AUTO_PST | S3C_ADCTSC_XY_PST(0))
 
static void __iomem     *ts_base;
static struct resource  *ts_mem;
static struct resource  *ts_irq;
static struct clk       *ts_clock;
static struct s3c_ts_info   *ts;
 
/**
 * get_down - return the down state of the pen
 * @data0: The data read from ADCDAT0 register.
 * @data1: The data read from ADCDAT1 register.
 *
 * Return non-zero if both readings show that the pen is down.
 */
static inline bool get_down(unsigned long data0, unsigned long data1)
{
    /* returns true if both data values show stylus down */
    return (!(data0 & S3C_ADCDAT0_UPDOWN) && !(data1 & S3C_ADCDAT1_UPDOWN)); //判断data0,data1最高位是否仍为"0"，为“0”表示触摸笔状态保持为down
}
 
 
/*===========================================================================================
    touch_timer_fire这个函数主要实现以下功能：
     
    1、  触摸笔开始点击的时候， 在中断函数stylus_updown里面被调用，
         此时缓存区没有数据，ts.count为0,   并且开启AD转换,而后进入 AD 中断
          
    2、  ADC中断函数stylus_action把缓冲区填满的时候，作为中断后半段函数稍后被调用（由内核定时器触发中断），
         此时ts.count为4，算出其平均值后，交给事件处理层(Event Handler)处理，
         主要是填写缓冲，然后唤醒等待输入数据的进程。
          
    3、  stylus抬起，等到缓冲区填满后(可能会包含一些无用的数据)被调用，
         这时候判断出stylus up，报告stylus up事件，重新等待stylus down。
============================================================================================*/
 
static void touch_timer_fire(unsigned long data) {
    unsigned long data0;
    unsigned long data1;
    int pendown;
 
#ifdef CONFIG_MINI6410_ADC
    if (!ADC_locked4TS()) {
        /* Note: pen UP interrupt detected and handled, the lock is released,
         * so do nothing in the timer which started by ADC ISR. */
        return;
    }
#endif
 
    data0 = readl(ts_base + S3C_ADCDAT0);
    data1 = readl(ts_base + S3C_ADCDAT1);//读取AD转换数据的值
 
    pendown = get_down(data0, data1);
 
    if (pendown) {
        if (ts->count == (1 << ts->shift)) {  //定时器触发touch_timer_fire中断时执行这个括号里
#ifdef CONFIG_TOUCHSCREEN_S3C_DEBUG
            {
                struct timeval tv;
                do_gettimeofday(&tv);
                printk(KERN_INFO "T: %06d, X: %03ld, Y: %03ld\n",
                        (int)tv.tv_usec, ts->xp, ts->yp);
            }
#endif
 
            ts_evt_add((ts->xp >> ts->shift), (ts->yp >> ts->shift), 1);//求平均，并写入fifo
 
            ts->xp = 0;
            ts->yp = 0;
            ts->count = 0;
        }
 
        /* start automatic sequencing A/D conversion */
        //每次按下有四次AD转换，以下为在按下中断中触发的第一次AD转换，其余三次在AD转换中断处理函数中触发
        //AUTOPST表示自动连续测量 以得到X位置，Y位置
        writel(S3C_ADCTSC_PULL_UP_DISABLE | AUTOPST, ts_base + S3C_ADCTSC);
        // 启动D转换，转换后会产生中断IRQ_ADC
        writel(readl(ts_base + S3C_ADCCON) | S3C_ADCCON_ENABLE_START,
                ts_base + S3C_ADCCON);
         
    } else {  //如果是松开，报告其触摸笔状态
        ts->xp = 0;
        ts->yp = 0;
        ts->count = 0;
 
        ts_evt_add(0, 0, 0);
 
        /* PEN is UP, Let's wait the PEN DOWN interrupt */
        writel(WAIT4INT(0), ts_base + S3C_ADCTSC);  // 设置INT 位，等待 DOWN 中断
 
#ifdef CONFIG_MINI6410_ADC
        if (ADC_locked4TS()) {
            s3c_ts_adc_unlock();
        }
#endif
    }
}
 
static DEFINE_TIMER(touch_timer, touch_timer_fire, 0, 0);
 
//触摸屏按下松开中断服务==
static irqreturn_t stylus_updown(int irqno, void *param)
{
#ifdef CONFIG_TOUCHSCREEN_S3C_DEBUG
    unsigned long data0;
    unsigned long data1;
    int is_waiting_up;
    int pendown;
#endif
 
#ifdef CONFIG_MINI6410_ADC
    if (!ADC_locked4TS()) {
        if (s3c_ts_adc_lock(LOCK_TS)) {
            /* Locking ADC controller failed */
            printk("Lock ADC failed, %d\n", adc_lock_id);
            return IRQ_HANDLED;
        }
    }
#endif
 
#ifdef CONFIG_TOUCHSCREEN_S3C_DEBUG
    data0 = readl(ts_base + S3C_ADCDAT0);
    data1 = readl(ts_base + S3C_ADCDAT1);
 
    is_waiting_up = readl(ts_base + S3C_ADCTSC) & (1 << 8);
    pendown = get_down(data0, data1);
 
    printk("P: %d <--> %c\n", pendown, is_waiting_up ? 'u':'d');
#endif
        //执行如下语句否则不断产生中断从而把系统卡死
    if (ts->s3c_adc_con == ADC_TYPE_2) {
        /* Clear ADC and PEN Down/UP interrupt */
        __raw_writel(0x0, ts_base + S3C_ADCCLRWK);
        __raw_writel(0x0, ts_base + S3C_ADCCLRINT);
    }
 
    /* TODO we should never get an interrupt with pendown set while
     * the timer is running, but maybe we ought to verify that the
     * timer isn't running anyways. */
 
    touch_timer_fire(1);
 
    return IRQ_HANDLED;
}
 
//ad转换结束中断服务程序==
static irqreturn_t stylus_action(int irqno, void *param)
{
    unsigned long data0;
    unsigned long data1;
 
#ifdef CONFIG_MINI6410_ADC
    if (!ADC_locked4TS()) {
        if (ADC_free()) {
            printk("Unexpected\n");
 
            /* Clear ADC interrupt */
            __raw_writel(0x0, ts_base + S3C_ADCCLRINT);
        }
 
        return IRQ_HANDLED;
    }
#endif
 
    data0 = readl(ts_base + S3C_ADCDAT0);
    data1 = readl(ts_base + S3C_ADCDAT1);
 
    if (ts->resol_bit == 12) {
#if defined(CONFIG_TOUCHSCREEN_NEW)
        ts->yp += S3C_ADCDAT0_XPDATA_MASK_12BIT - (data0 & S3C_ADCDAT0_XPDATA_MASK_12BIT);
        ts->xp += S3C_ADCDAT1_YPDATA_MASK_12BIT - (data1 & S3C_ADCDAT1_YPDATA_MASK_12BIT);
#else 
        ts->xp += data0 & S3C_ADCDAT0_XPDATA_MASK_12BIT;
        ts->yp += data1 & S3C_ADCDAT1_YPDATA_MASK_12BIT;
#endif
    } else {
#if defined(CONFIG_TOUCHSCREEN_NEW)
        ts->yp += S3C_ADCDAT0_XPDATA_MASK - (data0 & S3C_ADCDAT0_XPDATA_MASK);
        ts->xp += S3C_ADCDAT1_YPDATA_MASK - (data1 & S3C_ADCDAT1_YPDATA_MASK);
#else
        ts->xp += data0 & S3C_ADCDAT0_XPDATA_MASK;
        ts->yp += data1 & S3C_ADCDAT1_YPDATA_MASK;
#endif
    }  // 转换结果累加
 
    ts->count++;
 
    if (ts->count < (1 << ts->shift)) { // 采样未完成，继续下一次采样 ，通过 ENABLE_START 启动 AD 转换，一次一个数据
        writel(S3C_ADCTSC_PULL_UP_DISABLE | AUTOPST, ts_base + S3C_ADCTSC);
        writel(readl(ts_base + S3C_ADCCON) | S3C_ADCCON_ENABLE_START, ts_base + S3C_ADCCON);
    } else {  // 采样完毕，激活下半部处理程序touch_timer_fire，处理接收数据  
        mod_timer(&touch_timer, jiffies + 1);   //设置定时器超时的时间，目的是为了延时触发 touch_timer_fire 中断，如果在这段时间有抬起中断发生，则表示是抖动
                                                 //jiffies变量记录了系统启动以来，系统定时器已经触发的次数。内核每秒钟将jiffies变量增加HZ次。
                                                 //因此，对于HZ值为100的系统，1个jiffy等于10ms，而对于HZ为1000的系统，1个jiffy仅为1ms
                                                 
        writel(WAIT4INT(1), ts_base + S3C_ADCTSC);   //设置为等待抬起中断
    }
 
    if (ts->s3c_adc_con == ADC_TYPE_2) {
        /* Clear ADC and PEN Down/UP interrupt */
        __raw_writel(0x0, ts_base + S3C_ADCCLRWK);
        __raw_writel(0x0, ts_base + S3C_ADCCLRINT);
    }
 
    return IRQ_HANDLED;
}
 
 
#ifdef CONFIG_MINI6410_ADC
static unsigned int _adccon, _adctsc, _adcdly;
 
//其它模块要用ADC时，需要调用这个函数，来确定ADC是否可用，如果可用，则将它锁住，不让别的驱动用
int mini6410_adc_acquire_io(void) {
    int ret;
 
    ret = s3c_ts_adc_lock(LOCK_ADC); //锁住ADC，不让其它模块使用
    if (!ret) {  //如果ADC没有被使用，则保存ADC寄存器的值
        _adccon = readl(ts_base + S3C_ADCCON);
        _adctsc = readl(ts_base + S3C_ADCTSC);
        _adcdly = readl(ts_base + S3C_ADCDLY);
    }
 
    return ret;// 0:操作成功  1：操作失败
}
EXPORT_SYMBOL(mini6410_adc_acquire_io);  //声明为外部可用
 
//其它模块不要用ADC了，需要调用这个函数，来解锁ADC让别的驱动用
void mini6410_adc_release_io(void) {
        //还原ADC寄存器的设置
    writel(_adccon, ts_base + S3C_ADCCON);
    writel(_adctsc, ts_base + S3C_ADCTSC);
    writel(_adcdly, ts_base + S3C_ADCDLY);
    writel(WAIT4INT(0), ts_base + S3C_ADCTSC);
 
    s3c_ts_adc_unlock(); //释放ADC，其它模块可以使用
}
 
EXPORT_SYMBOL(mini6410_adc_release_io);
#endif
 
//获得触摸屏的配置信息==
static struct s3c_ts_mach_info *s3c_ts_get_platdata(struct device *dev)
{
    if (dev->platform_data != NULL)
        return (struct s3c_ts_mach_info *)dev->platform_data;  //优先使用 arch/arm/mach-s3c64xx中的定义
 
    return &s3c_ts_default_cfg;   //如果前面没定义，则使用本函数的default定义
}
//--
 
/*
 * The functions for inserting/removing us as a module.
 */
static int __init s3c_ts_probe(struct platform_device *pdev)
{
    struct resource *res;
    struct device *dev;
    struct s3c_ts_mach_info * s3c_ts_cfg;
    int ret, size;
 
    dev = &pdev->dev;
 
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (res == NULL) {
        dev_err(dev,"no memory resource specified\n");
        return -ENOENT;
    }
 
    size = (res->end - res->start) + 1;
    ts_mem = request_mem_region(res->start, size, pdev->name);
    if (ts_mem == NULL) {
        dev_err(dev, "failed to get memory region\n");
        ret = -ENOENT;
        goto err_req;
    }
 
    ts_base = ioremap(res->start, size);
    if (ts_base == NULL) {
        dev_err(dev, "failed to ioremap() region\n");
        ret = -EINVAL;
        goto err_map;
    }
 
    ts_clock = clk_get(&pdev->dev, "adc");
    if (IS_ERR(ts_clock)) {
        dev_err(dev, "failed to find watchdog clock source\n");
        ret = PTR_ERR(ts_clock);
        goto err_clk;
    }
 
    clk_enable(ts_clock);
 
    s3c_ts_cfg = s3c_ts_get_platdata(&pdev->dev);  //获取配置参数
         
    //设置ADC分频
    if ((s3c_ts_cfg->presc & 0xff) > 0)  
        writel(S3C_ADCCON_PRSCEN | S3C_ADCCON_PRSCVL(s3c_ts_cfg->presc & 0xff),
                ts_base + S3C_ADCCON);
    else
        writel(0, ts_base + S3C_ADCCON);
 
    /* Initialise registers */
    //设置转换延时
    if ((s3c_ts_cfg->delay & 0xffff) > 0)
        writel(s3c_ts_cfg->delay & 0xffff, ts_base + S3C_ADCDLY);
 
    if (s3c_ts_cfg->resol_bit == 12) {
        switch(s3c_ts_cfg->s3c_adc_con) {
            case ADC_TYPE_2:
                writel(readl(ts_base + S3C_ADCCON) | S3C_ADCCON_RESSEL_12BIT,
                        ts_base + S3C_ADCCON);
                break;
 
            case ADC_TYPE_1:
                writel(readl(ts_base + S3C_ADCCON) | S3C_ADCCON_RESSEL_12BIT_1,
                        ts_base + S3C_ADCCON);
                break;
 
            default:
                dev_err(dev, "Touchscreen over this type of AP isn't supported !\n");
                break;
        }
    }
 
    writel(WAIT4INT(0), ts_base + S3C_ADCTSC);
 
    ts = kzalloc(sizeof(struct s3c_ts_info), GFP_KERNEL);
 
    ts->shift = s3c_ts_cfg->oversampling_shift;
    ts->resol_bit = s3c_ts_cfg->resol_bit;
    ts->s3c_adc_con = s3c_ts_cfg->s3c_adc_con;
 
    /* For IRQ_PENDUP */
    ts_irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
    if (ts_irq == NULL) {
        dev_err(dev, "no irq resource specified\n");
        ret = -ENOENT;
        goto err_irq;
    }
 
    ret = request_irq(ts_irq->start, stylus_updown, IRQF_SAMPLE_RANDOM, "s3c_updown", ts);
    if (ret != 0) {
        dev_err(dev,"s3c_ts.c: Could not allocate ts IRQ_PENDN !\n");
        ret = -EIO;
        goto err_irq;
    }
 
    /* For IRQ_ADC */
    ts_irq = platform_get_resource(pdev, IORESOURCE_IRQ, 1);
    if (ts_irq == NULL) {
        dev_err(dev, "no irq resource specified\n");
        ret = -ENOENT;
        goto err_irq;
    }
 
    ret = request_irq(ts_irq->start, stylus_action, IRQF_SAMPLE_RANDOM | IRQF_SHARED,
            "s3c_action", ts);
    if (ret != 0) {
        dev_err(dev, "s3c_ts.c: Could not allocate ts IRQ_ADC !\n");
        ret = -EIO;
        goto err_irq;
    }
 
    printk(KERN_INFO "%s got loaded successfully : %d bits\n", DEVICE_NAME, s3c_ts_cfg->resol_bit);
 
    ret = misc_register(&misc);  //注册这混杂字符设备
    if (ret) {
        dev_err(dev, "s3c_ts.c: Could not register device(mini6410 touchscreen)!\n");
        ret = -EIO;
        goto fail;
    }
 
    return 0;
 
fail:
    free_irq(ts_irq->start, ts->dev);
    free_irq(ts_irq->end, ts->dev);
 
err_irq:
    kfree(ts);
 
    clk_disable(ts_clock);
    clk_put(ts_clock);
 
err_clk:
    iounmap(ts_base);
 
err_map:
    release_resource(ts_mem);
    kfree(ts_mem);
 
err_req:
    return ret;
}
 
static int s3c_ts_remove(struct platform_device *dev)
{
    printk(KERN_INFO "s3c_ts_remove() of TS called !\n");
 
    disable_irq(IRQ_ADC);
    disable_irq(IRQ_PENDN);
 
    free_irq(IRQ_PENDN, ts->dev);
    free_irq(IRQ_ADC, ts->dev);
 
    if (ts_clock) {
        clk_disable(ts_clock);
        clk_put(ts_clock);
        ts_clock = NULL;
    }
 
    misc_deregister(&misc);
    iounmap(ts_base);
 
    return 0;
}
 
#ifdef CONFIG_PM
static unsigned int adccon, adctsc, adcdly;
 
static int s3c_ts_suspend(struct platform_device *dev, pm_message_t state)
{
    adccon = readl(ts_base + S3C_ADCCON);
    adctsc = readl(ts_base + S3C_ADCTSC);
    adcdly = readl(ts_base + S3C_ADCDLY);
 
    disable_irq(IRQ_ADC);
    disable_irq(IRQ_PENDN);
 
    clk_disable(ts_clock);
 
    return 0;
}
 
static int s3c_ts_resume(struct platform_device *pdev)
{
    clk_enable(ts_clock);
 
    writel(adccon, ts_base + S3C_ADCCON);
    writel(adctsc, ts_base + S3C_ADCTSC);
    writel(adcdly, ts_base + S3C_ADCDLY);
    writel(WAIT4INT(0), ts_base + S3C_ADCTSC);
 
    enable_irq(IRQ_ADC);
    enable_irq(IRQ_PENDN);
    return 0;
}
#else
#define s3c_ts_suspend  NULL
#define s3c_ts_resume   NULL
#endif
 
static struct platform_driver s3c_ts_driver = {
    .probe          = s3c_ts_probe,
    .remove         = s3c_ts_remove,
    .suspend        = s3c_ts_suspend,
    .resume         = s3c_ts_resume,
    .driver         = {
        .owner          = THIS_MODULE,
        .name           = "s3c-ts",
    },
};
 
static char banner[] __initdata = KERN_INFO "S3C Touchscreen driver, (c) 2010 FriendlyARM,\n";
 
static int __init s3c_ts_init(void)
{
    printk(banner);
    return platform_driver_register(&s3c_ts_driver);
}
 
static void __exit s3c_ts_exit(void)
{
    platform_driver_unregister(&s3c_ts_driver);
}
 
module_init(s3c_ts_init);
module_exit(s3c_ts_exit);
 
MODULE_AUTHOR("FriendlyARM Inc.");
MODULE_LICENSE("GPL");
 
 
/*
 * 驱动分析
 * 1、内核是如何加载驱动的？
 *    首先要提到两个结构体：设备用Platform_device表示，驱动用Platform_driver进行注册
 *    Platform机制开发发底层驱动的大致流程为:  定义 platform_device  注册 platform_device 定义 platform_driver 注册 platform_driver
 *    首先要确认的就是设备的资源信息platform_device，例如设备的地址，中断号等 该结构体定义在kernel\include\linux\platform_device.h
 *    该结构一个重要的元素是resource，该元素存入了最为重要的设备资源信息，定义在kernel\include\linux\ioport.h中
 *    下面我们以本例来进行说明：
 *       arch/arm/mach-s3c64xx中dev-ts-mini6410.c中定义了platform_device s3c_device_ts
 *       定义好了platform_device结构体后就可以调用函数platform_add_devices向系统中添加该设备了，之后可以调用platform_driver_register()进行设备注册。
 *       要注意的是，这里的platform_device设备的注册过程必须在相应设备驱动加载之前被调用，即执行platform_driver_register之前,原因是因为驱动注册时需要
 *       匹配内核中所以已注册的设备名。
 *       platform_devicerr的注册是在arch/arm/mach-s3c64xx中mach-mini6410.c中的mini6410_machine_init函数实现的。
 *       mini6410_machine_init是在启动后调用，它是在module_init之前；更具体的见MACHINE_START
 *  MACHINE_START(MINI6410, "MINI6410")
 *       
 *        .boot_params  = S3C64XX_PA_SDRAM + 0x100,  //.boot_params是bootloader向内核传递的参数的位置，这要和bootloader中参数的定义要一致。
 *
 *        .init_irq = s3c6410_init_irq,  //.init_irq在start_kernel() --> init_IRQ() --> init_arch_irq()中被调用
 *        .map_io       = mini6410_map_io,   //.map_io 在 setup_arch() --> paging_init() --> devicemaps_init()中被调用
 *        .init_machine = mini6410_machine_init,  //init_machine 在 arch/arm/kernel/setup.c 中被 customize_machine 调用，
 *                          //放在 arch_initcall() 段里面，会自动按顺序被调用。
 *        .timer        = &s3c24xx_timer,  //.timer是定义系统时钟，定义TIMER4为系统时钟，在arch/arm/plat-s3c/time.c中体现。
 *                      //在start_kernel() --> time_init()中被调用。
 *       MACHINE_END
 *       再来看看platform_driver，这个定义在本文中，
 *       在驱动初始化函数中调用函数platform_driver_register()注册platform_driver，需要注意的是s3c_device_ts结构中name元素和s3c_ts_driver结构中driver.name
 *       必须是相同的，这样在platform_driver_register()注册时会对所有已注册的所有platform_device中的name和当前注册的platform_driver的driver.name进行比较，
 *       只有找到相同的名称的platfomr_device才能注册成功，当注册成功时会调用platform_driver结构元素probe函数指针，这里就是s3c_ts_probe
 *       参考资料：http://blogold.chinaunix.net/u2/60011/showart.php?id=1018502
 * 
 * 2、timer在这里的作用
 *     timer是用来防抖的，我们知道，触摸屏处理分为两个时间段，一个是由按下中断触发的四次AD转换的时间A，一个是4次AD转换完成后将AD数据存入FIFO的时间B，在时间A，没有打开抬起中断，
 *     也就是说如果在这段时间有抬起事件，也不会触发中断，不会影响AD的转换。在时间B，打开抬起中断，打开定时器延时触发touch_timer_fire，如果在延时这段时间，有抬起事件发生
 *      则touch_timer_fire不会将前面的数据存入到FIFO中，否则写入FIFO，表示值有效。
 * 
 * 
 */