这两天参考网上的资料，自己写了个SPI的驱动，并实际测试通过。
硬件平台：mini2440 用的是S3C2440 的SPI1（共有2个SPI模块）
操作系统：linux-2.6.32.2
测试方法：将SPI的MISO与MOSI管脚短路，这样读数据的时候第一个发出的dummy字节即为收到的字节。
下面是驱动的源代码(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");
几点需要注意的地方：
1.一开始在spi_exit()函数中使用了void unregister_chrdev(unsigned int major, const char *name)函数来注销设备，但再次insmod驱动的时候提示"Device or resource busy"，改为unregister_chrdev_region()后一切正常，说明即使只注册了一个设备，register_chrdev_region()和unregister_chrdev_region()也要配套使用。
2.定义spi_spcon1等寄存器变量时前面要加上volatile关键字，这样每次访问该变量时cpu会从实际内存中读取该值而不是使用寄存器中的值。尤其是spi_spsta1变量，它的最低位代表了spi发送接收是否ready，如果没有volatile，可能会在readByte()或writeByte()函数中导致死循环。
3.使用了module_param()宏向驱动传递参数，这里定义了一个int型的loopChar参数，加载模块时使用insmod mini2440_spi.ko loopChar=123 来设置loopChar的值。
测试程序：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;
}
很简单的一个程序，分别调用了open,write,read,close函数，可以观察输出结果，验证驱动程序是否正确，read的输出即为loopChar的值。
注意：open的时候要注意第二个参数flag，只有当flag为O_RDWR时，驱动中的相应的spi_read,spi_write函数才会被调用。
在乎的是看风景的心情，旅行不会因为美丽的风景终止。
