pcDuino Linux驱动开发五 -- 最简单的PWM驱动

tjcfeng

其实比较来说，PWM比中断还要简单，只不过一般刚接触的板子首先实现的都是基本的IO，所以把PWM安排在了中断之后。为了不使帖子看起来内容太少，这个程序将两路PWM 放在了一起，不过也是多了几个寄存器的设置而已。
另外要吐槽一下A10，PWM少就不说什么了，居然计数寄存器只有8位。是的，只有8位，最大到255而已，这个也太弱了吧

还有预分频，也只有这么几个

看到0101...0111那几个了吗？经过尝试后，发现其实是起作用的，是/720、/840、/960，后面的1101...1111是84K、96K、108K，权当一点补偿吧。
下面上程序，跟GPIO的一样，还是精简得不能再精简了。接线方式没来得及拍照，后面补上。

• #include <linux/init.h>
  
• #include <linux/module.h>
  
• #include <linux/fs.h>
  
• #include <linux/cdev.h>
  
• #include <linux/device.h>
  
• #include <linux/wait.h>
  
• #include <linux/delay.h>
  
• #include <asm/io.h>
  
• #include <asm/uaccess.h>
  
• #include "../A10.h"
  
• /**********************************************************************/
  
•      #define PWM_CH0            2
  
•      volatile static unsigned long* REG_PB_CFG0;
  
•      volatile static unsigned long* REG_PI_CFG0;
  
•      volatile static unsigned long* REG_PWM_CTRL_REG;
  
•      volatile static unsigned long* REG_PWM_CH0_PERIOD;
  
•      volatile static unsigned long* REG_PWM_CH1_PERIOD;
  
• 
  
•      static int Inited = 0;
  
• static int PWM_open(struct inode* n, struct file* f)
  
• {
  
•      int Result = 0;
  
•      Inited++;
  
•      if (Inited > 1)
  
•      {
  
•             return 0;
  
•      }
  
•      REG_PB_CFG0 = (volatile unsigned long*) ioremap(PB_CFG0, 4);
  
•      REG_PI_CFG0 = (volatile unsigned long*) ioremap(PI_CFG0, 4);
  
•      REG_PWM_CTRL_REG = (volatile unsigned long*) ioremap(PWM_CTRL_REG, 4);
  
•      REG_PWM_CH0_PERIOD= (volatile unsigned long*) ioremap(PWM_CH0_PERIOD, 4);
  
•      REG_PWM_CH1_PERIOD= (volatile unsigned long*) ioremap(PWM_CH1_PERIOD, 4);
  
• 
  
• 
  
•      *REG_PB_CFG0 &= ~(0x7 << 8) ;
  
•      *REG_PB_CFG0 |= (0x2 << 8) ; //PWM0
  
• 
  
•      *REG_PI_CFG0 &= ~(0x7 << 12) ;
  
•      *REG_PI_CFG0 |= (0x2 << 12) ; //PWM1
  
•      *REG_PWM_CH0_PERIOD = (249 << 16) + 5;
  
•      *REG_PWM_CTRL_REG |= (0xF << 0);
  
•      *REG_PWM_CTRL_REG |= (0x0 << 8) + (0x0 << 7) + (0x1 << 6) + (0x0 << 5);
  
•      *REG_PWM_CTRL_REG |= (0x1 << 4);
  
• 
  
•      *REG_PWM_CH1_PERIOD = (249 << 16) + 5;
  
•      *REG_PWM_CTRL_REG |= (0x8 << 15);
  
•      *REG_PWM_CTRL_REG |= (0x0 << 23) + (0x0 << 22) + (0x1 << 21) + (0x1 << 20);
  
•      *REG_PWM_CTRL_REG |= (0x1 << 19);
  
•      printk("Open Finished!\n");
  
•      return Result;
  
• }
  
• static ssize_t PWM_write(struct file* f, const char __user* buf, size_t len, loff_t* l)
  
• {
  
•      //printk("Write Finished!\n");
  
•      return 0;
  
• }
  
• static ssize_t PWM_read(struct file* f, char __user* buf, size_t len, loff_t* l)
  
• {
  
•      //printk("Read Finished!\n");
  
•      return 0;
  
• }
  
• static int PWM_close(struct inode* n, struct file* f)
  
• {
  
•      Inited--;
  
•      if (Inited > 0)
  
•      {
  
•             return 0;
  
•      }
  
•      *REG_PWM_CTRL_REG = 0;
  
•      *REG_PWM_CH0_PERIOD = 0;
  
•      *REG_PWM_CH1_PERIOD = 0;
  
• 
  
•      iounmap(REG_PB_CFG0);
  
•      iounmap(REG_PI_CFG0);
  
•      iounmap(REG_PWM_CTRL_REG);
  
•      iounmap(REG_PWM_CH0_PERIOD);
  
•      iounmap(REG_PWM_CH1_PERIOD);
  
•      printk("Close Finished!\n");
  
•      return 0;
  
• }
  
• /**********************************************************************/
  
•      #define DEV_NAME     &quotWM"
  
•      #define DEV_COUNT     1
  
•      static struct class* pClass;
  
•      int major;
  
• 
  
•      static struct file_operations fops =
  
•      {
  
•             .owner = THIS_MODULE,
  
•             .open = PWM_open,
  
•             .write = PWM_write,
  
•             .read = PWM_read,
  
•             .release = PWM_close,
  
•      };
  
• static int __init PWM_init(void)
  
• {
  
•      major = register_chrdev(0, DEV_NAME, &fops);
  
•      pClass = class_create(THIS_MODULE, DEV_NAME);
  
•      if (pClass == NULL)
  
•      {
  
•             unregister_chrdev(major, DEV_NAME);
  
•             return -1;
  
•      }
  
•      device_create(pClass, NULL, MKDEV(major, 0), NULL, DEV_NAME);
  
• 
  
•      PWM_open(NULL, NULL);
  
•      //printk("Init Finished!\n");
  
•      return 0;
  
• }
  
• static void __exit PWM_exit(void)
  
• {
  
•      PWM_close(NULL, NULL);
  
• 
  
•      unregister_chrdev(major, DEV_NAME);
  
•      if (pClass)
  
•      {
  
•             device_destroy(pClass, MKDEV(major, 0));
  
•             class_destroy(pClass);
  
•      }
  
•      //printk("Exit Finished!\n");
  
• }
  
• MODULE_LICENSE("GPL");
  
• MODULE_AUTHOR("LiuYang");
  
• module_init(PWM_init);
  
• module_exit(PWM_exit);