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ARM-Linux驱动--Watch Dog Timer(看门狗)驱动分析

时间：11-20 来源：互联网 点击：

  1. rtbeat(inttimeout)
  2. {
  3. unsignedintfreq=clk_get_rate(wdt_clock);
  4. unsignedintcount;
  5. unsignedintdivisor=1;
  6. unsignedlongwtcon;
  8. if(timeout<1)
  9. return-EINVAL;
  11. freq/=128;
  12. count=timeout*freq;
  14. /*ifthecountisbiggerthanthewatchdogregister,
  15. thenworkoutwhatweneedtodo(andif)wecan
  16. actuallymakethisvalue
  17. */
  18. //如果计时的时间过大，则适当加大预分频值
  19. if(count>=0x10000)
  20. {
  21. for(divisor=1;divisor<=0x100;divisor++)
  22. {
  23. if((count/divisor)<0x10000)
  24. break;
  25. }
  26. //若预分频最大仍不能满足计时周期，则报错
  27. if((count/divisor)>=0x10000)
  28. {
  29. dev_err(wdt_dev,"timeout%dtoobig\n",timeout);
  30. return-EINVAL;
  31. }
  32. }
  34. tmr_margin=timeout;
  36. count/=divisor;
  37. wdt_count=count;
  39. /*updatethepre-scaler*/
  40. wtcon=readl(wdt_base+S3C2410_WTCON);
  41. wtcon&=~S3C2410_WTCON_PRESCALE_MASK;
  42. wtcon|=S3C2410_WTCON_PRESCALE(divisor-1);
  44. writel(count,wdt_base+S3C2410_WTDAT);//是指WTDAT寄存器
  45. writel(wtcon,wdt_base+S3C2410_WTCON);//设置预分频值
  47. return0;
  48. }
  50. /*
  51. */dev/watchdoghandling
  52. */
  54. staticints3c2410wdt_open(structinode*inode,structfile*file)
  55. {
  56. if(test_and_set_bit(0,&open_lock))//测试并设置open_lock第0位为1
  57. return-EBUSY;
  58. if(nowayout)
  59. __module_get(THIS_MODULE);
  61. allow_close=CLOSE_STATE_NOT;
  63. /*startthetimer*/
  64. s3c2410wdt_start();//启动watchdog
  65. returnnonseekable_open(inode,file);
  66. }
  68. staticints3c2410wdt_release(structinode*inode,structfile*file)
  69. {
  70. /*
  71. *Shutoffthetimer.
  72. *Lockitinifitsamoduleandwesetnowayout
  73. */
  75. if(allow_close==CLOSE_STATE_ALLOW)
  76. s3c2410wdt_stop();
  77. else
  78. {
  79. dev_err(wdt_dev,"Unexpectedclose,notstoppingwatchdog\n");
  80. s3c2410wdt_keepalive();
  81. }
  82. allow_close=CLOSE_STATE_NOT;
  83. clear_bit(0,&open_lock);//清楚open_lock第0位
  84. return0;
  85. }
  87. staticssize_ts3c2410wdt_write(structfile*file,constchar__user*data,
  88. size_tlen,loff_t*ppos)
  89. {
  90. /*
  91. *Refreshthetimer.
  92. */
  93. if(len)
  94. {
  95. if(!nowayout)
  96. {
  97. size_ti;
  98. /*Incaseitwassetlongago*/
  99. allow_close=CLOSE_STATE_NOT;
  101. for(i=0;i!=len;i++)
  102. {
  103. charc;
  104. if(get_user(c,data+i))//从用户空间copy数据
  105. return-EFAULT;
  106. if(c==V)//当输入V时，关闭watchdog
  107. allow_close=CLOSE_STATE_ALLOW;
  108. }
  109. }
  110. //注意：这里要手动喂狗一次?!
  111. s3c2410wdt_keepalive();//由于将allow_close设置成CLOSE_STATE_ALLOW后，当release时无法再次喂狗
  112. }
  113. returnlen;
  114. }
  116. #defineOPTIONSWDIOF_SETTIMEOUT|WDIOF_KEEPALIVEPING|WDIOF_MAGICCLOSE
  118. staticconststructwatchdog_infos3c2410_wdt_ident=
  119. {
  120. .options=OPTIONS,
  121. .firmware_version=0,
  122. .identity="S3C2410Watchdog",
  123. };
  125. //IO控制接口函数
  126. staticlongs3c2410wdt_ioctl(structfile*file,unsignedintcmd,
  127. unsignedlongarg)
  128. {
  129. void__user*argp=(void__user*)arg;
  130. int__user*p=argp;
  131. intnew_margin;
  133. switch(cmd){
  134. caseWDIOC_GETSUPPORT:
  135. returncopy_to_user(argp,&s3c2410_wdt_ident,
  136. sizeof(s3c2410_wdt_ident))?-EFAULT:0;
  137. caseWDIOC_GETSTATUS:
  138. caseWDIOC_GETBOOTSTATUS:
  139. returnput_user(0,p);
  140. caseWDIOC_KEEPALIVE:
  141. s3c2410wdt_keepalive();
  142. return0;
  143. caseWDIOC_SETTIMEOUT:
  144. if(get_user(new_margin,p))
  145. return-EFAULT;
  146. if(s3c2410wdt_set_heartbeat(new_margin))
  147. return-EINVAL;
  148. s3c2410wdt_keepalive();
  149. returnput_user(tmr_margin,p);
  150. caseWDIOC_GETTIMEOUT:
  151. returnput_user(tmr_margin,p);
  152. default:
  153. return-ENOTTY;
  154. }
  155. }
  157. /*kernelinterface*/
  159. //文件操作结构体
  160. staticconststructfile_operationss3c2410wdt_fops=
  161. {
  162. .owner=THIS_MODULE,
  163. .llseek=no_llseek,//屏蔽seek操作
  164. .write=s3c2410wdt_write,//写方法
  165. .unlocked_ioctl=s3c2410wdt_ioctl,//控制方法
  166. .open=s3c2410wdt_open,//代开设备方法
  167. .release=s3c2410wdt_release,//关闭设备方法
  168. };
  170. staticstructmiscdevices3c2410wdt_miscdev=
  171. {
  172. .minor=WATCHDOG_MINOR,
  173. .name="watchdog",
  174. .fops=&s3c2410wdt_fops,
  175. };
  177. /*interrupthandlercode*/
  179. staticirqreturn_ts3c2410wdt_irq(intirqno,void*param)
  180. {
  181. //dev_info(wdt_dev,"watchdogtimerexpired(irq)\n");
  182. s3c2410_gpio_setpin(S3C2410_GPB10,(count++)%2);
  183. s3c2410wdt_keepalive();
  184. returnIRQ_HANDLED;
  185. }
  186. /*deviceinterface*/
  188. //注册设备时执行
  189. staticints3c2410wdt_probe(structplatform_device*pdev)
  190. {
  191. structresource*res;
  192. structdevice*dev;
  193. unsignedintwtcon;
  194. intstarted=0;
  195. intret;
  196. intsize;
  198. dev=&pdev->dev;
  199. wdt_dev=&pdev->dev;
  201. /*getthememoryregionforthewatchdogtimer*/

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