基於Linux構建無人值守系統（看門狗）

在各種嵌入式設備soc中基本都提供了看門狗，在很長一段時間裡我對看門狗的理解就是“關掉它，不然它會找麻煩”。但是當某種需求存在的時候，它又是必不可少的，比如你的產品是一個類似路由器的服務設備，可能在陽台的某刻角落一丟就是好幾年，雖然孤獨聽起來讓人傷感，可是如果在孤獨中死去，那就會給客戶帶來更大的煩惱。所以我們應該去了解它

講解中使用的環境主要基於linux系統，設備是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. //狗中斷
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. //啟動喂狗定時器
76. setup_timer(&wdtdrv->timer, wdt_timeout,(unsigned long)wdtdrv);
77. mod_timer(&wdtdrv->timer,jiffies+HZ/2);
79. //狗超時中斷
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停止運行
90. iowrite32(0x80<<8|0<<5|0x3<<3|1,wdtdrv->regs);
92. //啟動喂狗定時器
93. del_timer(&wdtdrv->timer);
95. //狗超時中斷
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. //獲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. //獲取中斷
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");

首先對模塊進行初始化

module_init(modinit);

module_exit(modexit);

從平台中通過文件名"s3c2410-wdt"找出設備，回調wdt_probe

當然你的確定arch/arm/mach-s3c64xx/mach-s3c6410的static struct platform_device *smdk6410_devices[] __initdata中找到&s3c_device_wdt,，如果沒有，看看arch/arm/plat-samsung/中有沒有dev-wdt.c文件搞到裡面的platform_device對象，添加到__initdata中。