基于Linux构建无人值守系统（看门狗）


在各种嵌入式设备soc中基本都提供了看门狗，在很长一段时间里我对看门狗的理解就是“关掉它，不然它会找麻烦”。但是当某种需求存在的时候，它又是必不可少的，比如你的产品是一个类似路由器的服务设备，可能在阳台的某刻角落一丢就是好几年，虽然孤独听起来让人伤感，可是如果在孤独中死去，那就会给客户带来更大的烦恼。所以我们应该去了解它

讲解中使用的环境主要基于linux系统，设备是arm s3c6410

  1. #include <linux/io.h>
  2. #include <linux/init.h>
  3. #include <linux/module.h>
  4. #include <linux/platform_device.h>
  5. #include <linux/delay.h>
  6. #include <linux/interrupt.h>
  7. #include <linux/clk.h>
  10. staticint wdt_probe(struct platform_device * dev);
  11. staticint wdt_remove(struct platform_device * dev);
  15. struct wdt_driver
  16. {
  17. struct platform_driver pdrv;
  18. unsigned long phys_regs;
  19. unsigned long phys_regs_len;
  21. struct timer_list timer;
  22. int irq;
  23. void * regs;
  25. };
  27. staticstruct wdt_driver wdtdrv =
  28. {
  29. .pdrv =
  30. {
  31. .probe = wdt_probe,
  32. .remove = wdt_remove,
  33. .driver =
  34. {
  35. .name = "s3c2410-wdt",
  36. .owner = THIS_MODULE,
  37. },
  38. },
  39. };
  41. irqreturn_t wdt_irq(int irq,void * data)
  42. {
  43. struct wdt_driver * wdtdrv = data;
  44. iowrite32(1,wdtdrv->regs+0xc);
  45. printk("wdt_irq\n");
  47. return IRQ_HANDLED;
  48. }
  50. void wdt_timeout(unsigned long data)
  51. {//喂狗
  52. struct wdt_driver * wdtdrv = (void *)data;
  53. //printk("wdt_timeout\n");
  54. iowrite32(3764,wdtdrv->regs+8);
  55. mod_timer(&wdtdrv->timer,jiffies+HZ/2);
  56. }
  59. //pclk 66500000
  60. staticint wdt_init(struct wdt_driver * wdtdrv)
  61. {
  63. iowrite32(3764,wdtdrv->regs+4);
  64. iowrite32(3764,wdtdrv->regs+8);
  66. //狗中断
  67. //iowrite32(0x80<<8|0x1<<5|0x1<<2|0x3<<3,wdtdrv->regs);
  68. //狗reset
  69. iowrite32(0x80<<8|0x1<<5|0x3<<3|1,wdtdrv->regs);
  71. printk("WTCON=%x\n",ioread32(wdtdrv->regs));
  72. printk("WTDAT=%x\n",ioread32(wdtdrv->regs+4));
  73. printk("WTCNT=%x\n",ioread32(wdtdrv->regs+8));
  75. //启动喂狗定时器
  76. setup_timer(&wdtdrv->timer, wdt_timeout,(unsigned long)wdtdrv);
  77. mod_timer(&wdtdrv->timer,jiffies+HZ/2);
  79. //狗超时中断
  80. // if(!request_irq(wdtdrv->irq,wdt_irq,IRQF_TRIGGER_FALLING,"wdt",wdtdrv))
  81. // goto err_timer;
  83. return 0;
  85. }
  87. staticint wdt_destroy(struct wdt_driver * wdtdrv)
  88. {
  89. //狗timer停止运行
  90. iowrite32(0x80<<8|0<<5|0x3<<3|1,wdtdrv->regs);
  92. //启动喂狗定时器
  93. del_timer(&wdtdrv->timer);
  95. //狗超时中断
  96. //free_irq(wdtdrv->irq,(unsigned long)wdtdrv);
  97. return 0;
  98. }
  100. staticint wdt_probe(struct platform_device * dev)
  101. {
  102. struct wdt_driver * wdtdrv;
  103. struct resource * res;
  105. printk("wdt_probe:%s\n",dev->name);
  107. wdtdrv = container_of(container_of(dev->dev.driver,struct platform_driver,driver),struct wdt_driver,pdrv);
  110. //获取控制器寄存器地址
  111. res = platform_get_resource(dev,IORESOURCE_MEM,0);
  112. if(!res)
  113. goto err_out;
  115. wdtdrv->phys_regs = res->start;
  116. wdtdrv->phys_regs_len = res->end-res->start;
  119. wdtdrv->regs = ioremap(wdtdrv->phys_regs,wdtdrv->phys_regs_len);
  120. if(!wdtdrv->regs)
  121. goto err_out;
  123. if(!request_mem_region(wdtdrv->phys_regs,wdtdrv->phys_regs_len,dev_name(&dev->dev)))
  124. goto err_ioremap;
  126. //获取中断
  127. wdtdrv->irq = platform_get_irq(dev,0);
  128. if(wdtdrv->irq<0)
  129. goto err_request_mem;
  130. printk("irq=%d\n",wdtdrv->irq);
  132. wdt_init(wdtdrv);
  134. return 0;
  136. err_request_mem:
  137. release_mem_region(wdtdrv->phys_regs,wdtdrv->phys_regs_len);
  138. err_ioremap:
  139. iounmap(wdtdrv->regs);
  140. err_out:
  141. return -1;
  142. }
  144. staticint wdt_remove(struct platform_device * dev)
  145. {
  146. struct wdt_driver * wdtdrv;
  148. printk("wdt_remove:%s\n",dev->name);
  154. wdtdrv = container_of(container_of(dev->dev.driver,struct platform_driver,driver),struct wdt_driver,pdrv);
  156. wdt_destroy(wdtdrv);
  157. release_mem_region(wdtdrv->phys_regs,wdtdrv->phys_regs_len);
  158. iounmap(wdtdrv->regs);
  160. return 0;
  161. }
  165. staticint modinit(void)
  166. {
  167. printk("mod init\n");
  168. platform_driver_register(&wdtdrv.pdrv);
  169. return 0;
  170. }
  172. staticvoid modexit(void)
  173. {
  174. platform_driver_unregister(&wdtdrv.pdrv);
  175. printk("mod exit\n");
  176. }
  181. module_init(modinit);
  182. module_exit(modexit);
  184. MODULE_LICENSE("GPL");
  185. MODULE_AUTHOR("dragon101788");

首先对模块进行初始化

module_init(modinit);

module_exit(modexit);

从平台中通过文件名"s3c2410-wdt"找出设备，回调wdt_probe

当然你的确定arch/arm/mach-s3c64xx/mach-s3c6410的static struct platform_device *smdk6410_devices[] __initdata中找到&s3c_device_wdt,，如果没有，看看arch/arm/plat-samsung/中有没有dev-wdt.c文件搞到里面的platform_device对象，添加到__initdata中。

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