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。