原文地址：http://www.cnblogs.com/liu_xf/archive/2011/06/22/2086750.html
摘要：
分析内核s3c-ts.c源码，看它是如何采集坐标信息及防抖动处理的。
介绍：
直接上源码吧，完全注释：
/* 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。
*
*
*/