嵌入式 linux 驱动 ADC驱动

2019-07-12 18:02发布


    很懒,很久没去总结学习的东西,今天就总结下linux下的AD驱动吧,AD驱动理解的难点和注意的地方其实就只有两点。 一、虚拟地址的应用,就是物理地址转换为虚拟地址,ADC驱动程序中的寄存器就是都用      到了虚拟地址了。其中最主要的转换的语句是 base_addr=ioremap(S3C2410_PA_ADC,0x20);/ ioremap()功能: 将一个IO地址空间映射到内核的虚拟地址空间上去,返回值就是虚拟地址。  物理地址和虚拟地址的转换,就是将S3C2410_PA_ADC物理地址转换为base_addr 的地址。 S3C2410_PA_ADC 为物理地址0x58000000 ,具体也不知在那个文件能找到 。base_addr 虚拟地址,应该是有系统分配的,调用ioremap()既能分配到。 而base_addr 的定义是 static void __iomem *base_addr; 使用完后需要 iounmap(base_addr);释放掉虚拟地址。 二、时钟CLK的调用,用ADC需要用到CLK时钟,主要有已下几个函数: clk_get 
clk_use() 
clk_enable() 

这几个 函数的使用,当然再最后也要卸载掉,其函数如下   clk_disable(adc_clock);
  clk_put(adc_clock);
  adc_clock = NULL;
 } 还有可以参考如下网页 http://www.unixresources.net/linux/clf/driver/archive/00/00/65/81/658138.html http://hi.baidu.com/mystreetzone/blog/item/f36fca35d373001690ef39a7.html 最后附上具体程序
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#i nclude #i nclude "s3c24xx-adc.h" #undef DEBUG
//#define DEBUG
#ifdef DEBUG
#define DPRINTK(x...) {printk(____"(%d): ",__LINE__);printk(##x);}
#else
#define DPRINTK(x...) (void)(0)
#endif #define DEVICE_NAME "adc" static void __iomem *base_addr; typedef struct {
 wait_queue_head_t wait;
 int channel;
 int prescale;
}ADC_DEV; DECLARE_MUTEX(ADC_LOCK);
static int OwnADC = 0; static ADC_DEV adcdev;
static volatile int ev_adc = 0;
static int adc_data; static struct clk *adc_clock; #define ADCCON      (*(volatile unsigned long *)(base_addr + S3C2410_ADCCON)) //ADC control
#define ADCTSC      (*(volatile unsigned long *)(base_addr + S3C2410_ADCTSC)) //ADC touch screen control
#define ADCDLY      (*(volatile unsigned long *)(base_addr + S3C2410_ADCDLY)) //ADC start or Interval Delay
#define ADCDAT0     (*(volatile unsigned long *)(base_addr + S3C2410_ADCDAT0)) //ADC conversion data 0
#define ADCDAT1     (*(volatile unsigned long *)(base_addr + S3C2410_ADCDAT1)) //ADC conversion data 1
#define ADCUPDN     (*(volatile unsigned long *)(base_addr + 0x14)) //Stylus Up/Down interrupt status #define PRESCALE_DIS        (0 << 14)
#define PRESCALE_EN         (1 << 14)
#define PRSCVL(x)           ((x) << 6)
#define ADC_INPUT(x)        ((x) << 3)
#define ADC_START           (1 << 0)
#define ADC_ENDCVT          (1 << 15) #define START_ADC_AIN(ch, prescale)
 do{
  ADCCON = PRESCALE_EN | PRSCVL(prescale) | ADC_INPUT((ch)) ;
  ADCCON |= ADC_START;
 }while(0)
static irqreturn_t adcdone_int_handler(int irq, void *dev_id)
{
 if (OwnADC) {
  adc_data = ADCDAT0 & 0x3ff;   ev_adc = 1;
  wake_up_interruptible(&adcdev.wait);
 }  return IRQ_HANDLED;
} static ssize_t s3c2410_adc_read(struct file *filp, char *buffer, size_t count, loff_t *ppos)
{
 char str[20];
 int value;
 size_t len;
 if (down_trylock(&ADC_LOCK) == 0) {
  OwnADC = 1;
  START_ADC_AIN(adcdev.channel, adcdev.prescale);
  wait_event_interruptible(adcdev.wait, ev_adc);   ev_adc = 0;   DPRINTK("AIN[%d] = 0x%04x, %d ", adcdev.channel, adc_data, ADCCON & 0x80 ? 1:0);   value = adc_data;
  sprintf(str,"%5d", adc_data);
  copy_to_user(buffer, (char *)&adc_data, sizeof(adc_data));   OwnADC = 0;
  up(&ADC_LOCK);
 } else {
  value = -1;
 }  len = sprintf(str, "%d ", value);
 if (count >= len) {
  int r = copy_to_user(buffer, str, len);
  return r ? r : len;
 } else {
  return -EINVAL;
 }
} static int s3c2410_adc_open(struct inode *inode, struct file *filp)
{
 init_waitqueue_head(&(adcdev.wait));  adcdev.channel=0;
 adcdev.prescale=0xff;  DPRINTK( "adc opened ");
 return 0;
} static int s3c2410_adc_release(struct inode *inode, struct file *filp)
{
 DPRINTK( "adc closed ");
 return 0;
}
static struct file_operations dev_fops = {
 owner: THIS_MODULE,
 open: s3c2410_adc_open,
 read: s3c2410_adc_read, 
 release: s3c2410_adc_release,
}; static struct miscdevice misc = {
 .minor = MISC_DYNAMIC_MINOR,
 .name = DEVICE_NAME,
 .fops = &dev_fops,
}; static int __init dev_init(void)
{
 int ret;  base_addr=ioremap(S3C2410_PA_ADC,0x20);//功能: 将一个IO地址空间映射到内核的虚拟地址空间上去,便于访问; 
 /*
  物理地址和虚拟地址的转换,就是将S3C2410_PA_ADC物理地址转换为base_addr 的地址
  S3C2410_PA_ADC 为物理地址0x58000000 ,具体也不知在那个文件能找到
  base_addr 虚拟地址,应该是有系统分配的,调用ioremap()既能分配到
     */
 if (base_addr == NULL) {
  printk(KERN_ERR "Failed to remap register block ");
  return -ENOMEM;
 }  adc_clock = clk_get(NULL, "adc");
 if (!adc_clock) {
  printk(KERN_ERR "failed to get adc clock source ");
  return -ENOENT;
 }
 clk_enable(adc_clock);
 //用AD 需要打开CLK
 //既需要这两个函数clk_get()   clk_enable(adc_clock);  /* normal ADC */
 ADCTSC = 0;  ret = request_irq(IRQ_ADC, adcdone_int_handler, IRQF_SHARED, DEVICE_NAME, &adcdev);
 if (ret) {
  iounmap(base_addr);
  return ret;
 }  ret = misc_register(&misc);  printk (DEVICE_NAME" initialized ");
 return ret;
} static void __exit dev_exit(void)
{
 free_irq(IRQ_ADC, &adcdev);
 iounmap(base_addr);  if (adc_clock) {
  clk_disable(adc_clock);
  clk_put(adc_clock);
  adc_clock = NULL;
 }  misc_deregister(&misc);
} EXPORT_SYMBOL(ADC_LOCK);
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("FriendlyARM Inc.");