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這兩天參考網(wǎng)上的資料，自己寫(xiě)了個(gè)SPI的驅(qū)動(dòng)，并實(shí)際測(cè)試通過(guò)。

硬件平臺(tái)：mini2440 用的是S3C2440 的SPI1（共有2個(gè)SPI模塊）

操作系統(tǒng)：linux-2.6.32.2

測(cè)試方法：將SPI的MISO與MOSI管腳短路，這樣讀數(shù)據(jù)的時(shí)候第一個(gè)發(fā)出的dummy字節(jié)即為收到的字節(jié)。

下面是驅(qū)動(dòng)的源代碼(mini2440_spi.c)：

  /***************************************************/ 
  #include <linux/irq.h>  
  #include <linux/miscdevice.h>  
  #include <linux/delay.h>  
  #include <asm/irq.h>  
  #include <linux/interrupt.h>  
  #include <mach/regs-gpio.h>  
  #include <mach/hardware.h>  
  #include <linux/kernel.h>  
  #include <linux/module.h>  
  #include <linux/init.h>  
  #include <linux/mm.h>  
  #include <linux/fs.h>  
  #include <linux/types.h>  
  #include <linux/delay.h>  
  #include <linux/moduleparam.h>  
  #include <linux/slab.h>  
  #include <linux/errno.h>  
  #include <linux/ioctl.h>  
  #include <linux/cdev.h>  
  #include <linux/string.h>  
  #include <linux/list.h>  
  #include <linux/pci.h>  
  #include <linux/gpio.h>  
  #include <asm/uaccess.h>  
  #include <asm/atomic.h>  
  #include <asm/unistd.h>  
  #include <linux/spinlock.h>  
  #include <asm/system.h>  
  #include <asm/uaccess.h>  
     
  int loopChar=0x88;  
  module_param(loopChar,int,S_IRUGO);  
                                                         
  static int spi_major = 55;  
  #define spi_name "mini2440_spi"  
  struct cdev spiCdev;  
     
  /*****************************************************/ 
     
  static int spi_open(struct inode *,struct file *);  
  static int spi_release(struct inode *,struct file *);  
  static ssize_t spi_write(struct file *filp,const char *buf,size_t count,loff_t *f_ops);  
  static ssize_t spi_read(struct file *filp,char *buf,size_t count,loff_t *f_ops);  
  static ssize_t spi_ioctl(struct inode *inode,struct file *filp,unsigned int cmd,unsigned long data);  
     
  volatile int *spi_gpfcon=NULL;//GPF Part define  
  volatile int *spi_gpfdat=NULL;  
  volatile int *spi_gpfup=NULL;  
     
  volatile int *spi_gpgcon=NULL;//GPG Part define  
  volatile int *spi_gpgdat=NULL;  
  volatile int *spi_gpgup=NULL;  
     
  volatile int *s3c2440_clkcon;  
  volatile int *spi_spcon1;//SPI Part define  
  volatile int *spi_spsta1;  
  volatile int *spi_sppin1;  
  volatile int *spi_sppre1;  
  volatile int *spi_sptdat1;  
  volatile int *spi_sprdat1;  
     
  #define SPI_TXRX_READY      (((*spi_spsta1)&0x1) == 0x1)  
  /**********************************************************/ 
  static const struct file_operations spi_fops =   
  {  
      .owner=THIS_MODULE,  
      .open=spi_open,  
      .read=spi_read,  
      .ioctl=spi_ioctl,  
      .release=spi_release,  
      .write=spi_write,  
  };  
     
  /********************************************************/ 
  static int spi_open(struct inode *inode,struct file *filp)  
  {  
      filp->private_data =&spiCdev;      
      /***********************************************  
      *PCLK  
      ************************************************/ 
      /*control PCLK into spi block*/ 
      *s3c2440_clkcon |=0x40000;  
      printk("s3c2440_clkcon=%08X\n",*s3c2440_clkcon);  
      /***********************************************  
      *GPG PORTS  
      ************************************************/ 
      /*config SCK1,MOSI1,MISO1 = 11*/ 
      *spi_gpgcon |=0x0000FC00;  
      /*poll up MISO1 MOSI1,SCK1*/ 
      *spi_gpgup &=0xFF1F;  
      *spi_gpgup |=0x0060;  
      /***********************************************  
      *GPF PORTS  
      ************************************************/ 
      *spi_gpfcon &= 0xFCF3;  
      *spi_gpfcon |= 0x0108;    
      *spi_gpfup &= 0xED;  
      *spi_gpfdat |= 0x10;  
      /***********************************************  
      *SPI REGS  
      ************************************************/  
      //SPI Baud Rate Prescaler Register,Baud Rate=PCLK/2/(Prescaler value+1)  
      *spi_sppre1=0x18;       //freq = 1M  
      printk("spi_sppre1=%02X\n",*spi_sppre1);  
      //polling,en-sck,master,low,format A,nomal = 0 | TAGD = 1  
      *spi_spcon1=(0<<6)|(0<<5)|(1<<4)|(1<<3)|(0<<2)|(0<<1)|(0<<0);  
      printk("spi_spcon1=%02X\n",*spi_spcon1);  
      //Multi Master error detect disable,reserved,rech=*spi_sprdat0;lease  
      *spi_sppin1=(0<<2)|(0<<0);  
      printk("spi_sppin1=%02X\n",*spi_sppin1);  
     
      return 0;  
  }  
     
     
  static int spi_release(struct inode *inode,struct file *filp)  
  {  
      //free irq  
      free_irq(IRQ_EINT1, NULL);  
     
      printk("<1>release\n");  
      return 0;  
  }  
     
     
  static void writeByte(const char c)  
  {  
      int j = 0;  
      *spi_sptdat1 = c;  
      for(j=0;j<0xFF;j++);  
      while(!SPI_TXRX_READY)  
          for(j=0;j<0xFF;j++);  
  }  
     
  static char readByte(void)  
  {  
      int j = 0;  
      char ch = 0;  
      *spi_sptdat1 = (char)loopChar;  
      for(j=0;j<0xFF;j++);  
      while(!SPI_TXRX_READY)  
          for(j=0;j<0xFF;j++);  
      ch=*spi_sprdat1;  
      return ch;  
  }  
  static ssize_t spi_read(struct file *filp,char __user *buf,size_t count,loff_t *f_ops)  
  {  
      //int len=0;  
      char ch;  
      printk("<1>spi read!\n");  
      ch=readByte();  
      copy_to_user(buf,&ch,1);  
      return 1;  
  }  
     
  static ssize_t spi_write(struct file *filp,const char __user *buf,size_t count,loff_t *f_ops)  
  {  
      int i;  
      char *kbuf;  
      printk("<1>spi write!,count=%d\n",count);  
      kbuf=kmalloc(count,GFP_KERNEL);  
      if(copy_from_user(kbuf,buf,count))  
      {  
          printk("no enough memory!\n");  
          return -1;  
      }  
         
      for(i=0;i<count;i++)  
      {  
          writeByte(*kbuf);  
          printk("write 0x%02X!\n",*kbuf);  
          kbuf++;  
      }  
      return count;  
  }  
     
  static ssize_t spi_ioctl(struct inode *inode,struct file *filp,unsigned int cmd,unsigned long data)  
  {  
      return 0;  
  }  
     
     
  static int __init spi_init(void)  
  {  
      int result;  
      dev_t devno = MKDEV(spi_major, 0);  
     
      /**/ 
      if (spi_major)  
          result = register_chrdev_region(devno, 1, spi_name);  
      else  /**/ 
      {  
          result = alloc_chrdev_region(&devno, 0, 1, spi_name);  
          spi_major = MAJOR(devno);  
      }    
      if (result < 0)  
          return result;  
             
      cdev_init(&spiCdev, &spi_fops);  
      spiCdev.owner = THIS_MODULE;  
      spiCdev.ops = &spi_fops;  
      if (cdev_add(&spiCdev, devno, 1))  
          printk(KERN_NOTICE "Error adding spi %d", 0);  
     
      s3c2440_clkcon = (int *)ioremap(0x4C00000c,3);  
     
      spi_gpgcon = (int *)ioremap (0x56000060,4);  
      spi_gpgdat = (int *)ioremap (0x56000064,2);  
      spi_gpgup = (int *)ioremap (0x56000068,2);  
     
      spi_gpfcon = (int *)ioremap (0x56000050,2);  
      spi_gpfdat = (int *)ioremap (0x56000054,1);  
      spi_gpfup = (int *)ioremap (0x56000058,1);  
     
      spi_spcon1 = (int *)ioremap(0x59000020,1);  
      spi_spsta1 = (int *)ioremap(0x59000024,1);  
      spi_sppin1 = (int *)ioremap(0x59000028,1);  
      spi_sppre1 = (int *)ioremap(0x5900002c,1);  
      spi_sptdat1 = (int *)ioremap(0x59000030,1);  
      spi_sprdat1 = (int *)ioremap(0x59000034,1);  
     
     
      printk("Init spi success!\n");    
      return result;  
  }  
     
     
  static void __exit spi_exit(void)  
  {  
      cdev_del(&spiCdev);  
      unregister_chrdev_region(MKDEV(spi_major, 0), 1);  
      printk("<1>spi_exit!\n");  
  }  
     
  module_init(spi_init);  
  module_exit(spi_exit);  
     
  MODULE_LICENSE("GPL");  
  MODULE_AUTHOR("nkzc");  
  MODULE_DESCRIPTION("SPI driver for S3C2440"); 

幾點(diǎn)需要注意的地方：

1.一開(kāi)始在spi_exit()函數(shù)中使用了void unregister_chrdev(unsigned int major, const char *name)函數(shù)來(lái)注銷(xiāo)設(shè)備，但再次insmod驅(qū)動(dòng)的時(shí)候提示"Device or resource busy"，改為unregister_chrdev_region()后一切正常，說(shuō)明即使只注冊(cè)了一個(gè)設(shè)備，register_chrdev_region()和unregister_chrdev_region()也要配套使用。

2.定義spi_spcon1等寄存器變量時(shí)前面要加上volatile關(guān)鍵字，這樣每次訪問(wèn)該變量時(shí)cpu會(huì)從實(shí)際內(nèi)存中讀取該值而不是使用寄存器中的值。尤其是spi_spsta1變量，它的最低位代表了spi發(fā)送接收是否ready，如果沒(méi)有volatile，可能會(huì)在readByte()或writeByte()函數(shù)中導(dǎo)致死循環(huán)。

3.使用了module_param()宏向驅(qū)動(dòng)傳遞參數(shù)，這里定義了一個(gè)int型的loopChar參數(shù)，加載模塊時(shí)使用insmod mini2440_spi.ko loopChar=123 來(lái)設(shè)置loopChar的值。

測(cè)試程序：spi_test.c

  #include <stdio.h>  
  #include <stdlib.h>  
  #include <unistd.h>  
  #include <sys/ioctl.h>  
  #include<sys/types.h>  
  #include<sys/stat.h>  
  #include<fcntl.h>  
     
  int main(int argc, char **argv)  
  {  
      int fd;  
      int count=0;  
      char buf[]={0x11,0x22,0x33,0x44,0x55};  
      fd = open("/dev/mini2440_spi", O_RDWR);  
      if (fd < 0) {  
          perror("open device spi");  
          exit(1);  
      }  
      count=write(fd,buf,sizeof(buf)/sizeof(buf[0]));  
      read(fd,buf,1);  
      printf("read byte is: 0x%02X\n",buf[0]);  
      close(fd);  
      return 0;  
  } 

很簡(jiǎn)單的一個(gè)程序，分別調(diào)用了open,write,read,close函數(shù)，可以觀察輸出結(jié)果，驗(yàn)證驅(qū)動(dòng)程序是否正確，read的輸出即為loopChar的值。

注意：open的時(shí)候要注意第二個(gè)參數(shù)flag，只有當(dāng)flag為O_RDWR時(shí)，驅(qū)動(dòng)中的相應(yīng)的spi_read,spi_write函數(shù)才會(huì)被調(diào)用。

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