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        ARM-Linux驅動--Watch Dog Timer(看門狗)驅動分析
        
						
        
				作者：
				時間：2016-11-20
				來源：網絡

							
				
				
				
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			硬件平臺：FL2440
        內核版本：2.6.28
        本文引用地址：http://www.104case.com/article/201611/318869.htm
        主機平臺：Ubuntu 11,04
        內核版本：2.6.39
        1、看門狗驅動的原理
        下圖是看門狗驅動的原理圖
        可以看出，PCLK是系統時鐘，經過8位的預分頻，然后再被分頻（16、32、64、128）然后產生計數脈沖，進行計數，當計數器WTCNT加到0或減到0，然后產生中斷，或引起系統復位。所以要隔一段時間，重置WTCNT的值，防止WTCNT減到0，稱之“喂狗”。
        2、驅動分析
        下面是自己的驅動分析，如有理解錯誤，請指正
        注，為了盡量是驅動容易理解，這個驅動暫時將有關電源管理的功能刪除了，等理解透徹再完善
        1. #include
        2. #include
        3. #include
        4. #include
        5. #include
        6. #include
        7. #include
        8. #include
        9. #include
        10. #includeinterrupt.h>
        11. #include
        12. #include
        13. #include
        15. #include
        17. #include
        19. #undefS3C_VA_WATCHDOG
        20. #defineS3C_VA_WATCHDOG(0)
        22. #include
        24. #definePFX"s3c2410-wdt:"
        26. #defineCONFIG_S3C2410_WATCHDOG_ATBOOT(0)
        27. #defineCONFIG_S3C2410_WATCHDOG_DEFAULT_TIME(15)
        29. staticintnowayout=WATCHDOG_NOWAYOUT;
        30. staticinttmr_margin=CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME;
        31. staticinttmr_atboot=CONFIG_S3C2410_WATCHDOG_ATBOOT;
        32. staticintsoft_noboot=1;//設置默認為執行中斷
        33. staticintdebug;
        34. staticintcount;//用于計數，控制LED燈的亮滅
        36. module_param(tmr_margin,int,0);
        37. module_param(tmr_atboot,int,0);
        38. module_param(nowayout,int,0);
        39. module_param(soft_noboot,int,0);
        40. module_param(debug,int,0);
        42. MODULE_PARM_DESC(tmr_margin,"Watchdogtmr_margininseconds.default="
        43. __MODULE_STRING(CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME)")");
        44. MODULE_PARM_DESC(tmr_atboot,
        45. "Watchdogisstartedatboottimeifsetto1,default="
        46. __MODULE_STRING(CONFIG_S3C2410_WATCHDOG_ATBOOT));
        47. MODULE_PARM_DESC(nowayout,"Watchdogcannotbestoppedoncestarted(default="
        48. __MODULE_STRING(WATCHDOG_NOWAYOUT)")");
        49. MODULE_PARM_DESC(soft_noboot,"Watchdogaction,setto1toignorereboots,0to
        50. reboot(defaultdependsonONLY_TESTING)");
        51. MODULE_PARM_DESC(debug,"Watchdogdebug,setto>1fordebug,(default0)");
        54. typedefenumclose_state
        55. {
        56. CLOSE_STATE_NOT,
        57. CLOSE_STATE_ALLOW=0x4021
        58. }close_state_t;
        60. staticunsignedlongopen_lock;
        61. staticstructdevice*wdt_dev;/*platformdeviceattachedto*/
        62. staticstructresource*wdt_mem;//用來保存IO端口占用的內存資源
        63. staticstructresource*wdt_irq;//保存wdt中斷號
        64. staticstructclk*wdt_clock;//保存從平臺獲取的watchdog時鐘
        65. staticvoid__iomem*wdt_base;//經過ioremap后的內存基地址
        66. staticunsignedintwdt_count;//保存向WTCNT寫的計數值
        67. staticclose_state_tallow_close;
        68. staticDEFINE_SPINLOCK(wdt_lock);//定義一個自旋鎖，用于資源的互斥訪問
        70. /*watchdogcontrolroutines*/
        72. #defineDBG(msg...)do{
        73. if(debug)
        74. printk(KERN_INFOmsg);
        75. }while(0)
        77. /*functions*/
        79. //喂狗函數，實際上是將wdt_count寫入WTCNT寄存器
        80. staticvoids3c2410wdt_keepalive(void)
        81. {
        82. spin_lock(&wdt_lock);//給資源上鎖
        83. writel(wdt_count,wdt_base+S3C2410_WTCNT);//寫WTCNT寄存器
        84. spin_unlock(&wdt_lock);//解鎖資源,下同
        85. }
        87. staticvoid__s3c2410wdt_stop(void)
        88. {
        89. unsignedlongwtcon;
        91. wtcon=readl(wdt_base+S3C2410_WTCON);
        92. wtcon&=~(S3C2410_WTCON_ENABLE|S3C2410_WTCON_RSTEN);
        93. writel(wtcon,wdt_base+S3C2410_WTCON);//設備看門狗使能無效、復位功能無效
        94. }
        95. //停止watchdog計時
        96. staticvoids3c2410wdt_stop(void)
        97. {
        98. spin_lock(&wdt_lock);
        99. __s3c2410wdt_stop();
        100. spin_unlock(&wdt_lock);
        101. }
        103. //啟動watchdog計時
        104. staticvoids3c2410wdt_start(void)
        105. {
        106. unsignedlongwtcon;
        108. spin_lock(&wdt_lock);
        110. __s3c2410wdt_stop();
        112. wtcon=readl(wdt_base+S3C2410_WTCON);
        113. wtcon|=S3C2410_WTCON_ENABLE|S3C2410_WTCON_DIV128;//看門狗定時器使能、時鐘除數因子128
        115. if(soft_noboot)//使用參數soft_noboot來選擇看門狗到時是重啟還是執行中斷函數
        116. {
        117. wtcon|=S3C2410_WTCON_INTEN;//中斷使能
        118. wtcon&=~S3C2410_WTCON_RSTEN;//復位功能無效
        119. }
        120. else
        121. {
        122. wtcon&=~S3C2410_WTCON_INTEN;//中斷不使能
        123. wtcon|=S3C2410_WTCON_RSTEN;//復位功能有效
        124. }
        126. writel(wdt_count,wdt_base+S3C2410_WTDAT);//將wdt_count寫入WTDAT
        127. writel(wdt_count,wdt_base+S3C2410_WTCNT);//將wdt_count寫入WTCNT
        128. writel(wtcon,wdt_base+S3C2410_WTCON);//設置WTCON
        129. spin_unlock(&wdt_lock);
        130. }
        132. //設置WatchDog周期timeout
        133. staticints3c2410wdt_set_heartbeat(inttimeout)
        134. {
        135. unsignedintfreq=clk_get_rate(wdt_clock);
        136. unsignedintcount;
        137. unsignedintdivisor=1;
        138. unsignedlongwtcon;
        140. if(timeout<1)
        141. return-EINVAL;
        143. freq/=128;
        144. count=timeout*freq;
        146. /*ifthecountisbiggerthanthewatchdogregister,
        147. thenworkoutwhatweneedtodo(andif)wecan
        148. actuallymakethisvalue
        149. */
        150. //如果計時的時間過大，則適當加大預分頻值
        151. if(count>=0x10000)
        152. {
        153. for(divisor=1;divisor<=0x100;divisor++)
        154. {
        155. if((count/divisor)<0x10000)
        156. break;
        157. }
        158. //若預分頻最大仍不能滿足計時周期，則報錯
        159. if((count/divisor)>=0x10000)
        160. {
        161. dev_err(wdt_dev,"timeout%dtoobign",timeout);
        162. return-EINVAL;
        163. }
        164. }
        166. tmr_margin=timeout;
        168. count/=divisor;
        169. wdt_count=count;
        171. /*updatethepre-scaler*/
        172. wtcon=readl(wdt_base+S3C2410_WTCON);
        173. wtcon&=~S3C2410_WTCON_PRESCALE_MASK;
        174. wtcon|=S3C2410_WTCON_PRESCALE(divisor-1);
        176. writel(count,wdt_base+S3C2410_WTDAT);//是指WTDAT寄存器
        177. writel(wtcon,wdt_base+S3C2410_WTCON);//設置預分頻值
        179. return0;
        180. }
        182. /*
        183. */dev/watchdoghandling
        184. */
        186. staticints3c2410wdt_open(structinode*inode,structfile*file)
        187. {
        188. if(test_and_set_bit(0,&open_lock))//測試并設置open_lock第0位為1
        189. return-EBUSY;
        190. if(nowayout)
        191. __module_get(THIS_MODULE);
        193. allow_close=CLOSE_STATE_NOT;
        195. /*startthetimer*/
        196. s3c2410wdt_start();//啟動watchdog
        197. returnnonseekable_open(inode,file);
        198. }
        200. staticints3c2410wdt_release(structinode*inode,structfile*file)
        201. {
        202. /*
        203. *Shutoffthetimer.
        204. *Lockitinifitsamoduleandwesetnowayout
        205. */
        207. if(allow_close==CLOSE_STATE_ALLOW)
        208. s3c2410wdt_stop();
        209. else
        210. {
        211. dev_err(wdt_dev,"Unexpectedclose,notstoppingwatchdogn");
        212. s3c2410wdt_keepalive();
        213. }
        214. allow_close=CLOSE_STATE_NOT;
        215. clear_bit(0,&open_lock);//清楚open_lock第0位
        216. return0;
        217. }
        219. staticssize_ts3c2410wdt_write(structfile*file,constchar__user*data,
        220. size_tlen,loff_t*ppos)
        221. {
        222. /*
        223. *Refreshthetimer.
        224. */
        225. if(len)
        226. {
        227. if(!nowayout)
        228. {
        229. size_ti;
        230. /*Incaseitwassetlongago*/
        231. allow_close=CLOSE_STATE_NOT;
        233. for(i=0;i!=len;i++)
        234. {
        235. charc;
        236. if(get_user(c,data+i))//從用戶空間copy數據
        237. return-EFAULT;
        238. if(c==V)//當輸入V時，關閉watchdog
        239. allow_close=CLOSE_STATE_ALLOW;
        240. }
        241. }
        242. //注意：這里要手動喂狗一次?!
        243. s3c2410wdt_keepalive();//由于將allow_close設置成CLOSE_STATE_ALLOW后，當release時無法再次喂狗
        244. }
        245. returnlen;
        246. }
        248. #defineOPTIONSWDIOF_SETTIMEOUT|WDIOF_KEEPALIVEPING|WDIOF_MAGICCLOSE
        250. staticconststructwatchdog_infos3c2410_wdt_ident=
        251. {
        252. .options=OPTIONS,
        253. .firmware_version=0,
        254. .identity="S3C2410Watchdog",
        255. };
        257. //IO控制接口函數
        258. staticlongs3c2410wdt_ioctl(structfile*file,unsignedintcmd,
        259. unsignedlongarg)
        260. {
        261. void__user*argp=(void__user*)arg;
        262. int__user*p=argp;
        263. intnew_margin;
        265. switch(cmd){
        266. caseWDIOC_GETSUPPORT:
        267. returncopy_to_user(argp,&s3c2410_wdt_ident,
        268. sizeof(s3c2410_wdt_ident))?-EFAULT:0;
        269. caseWDIOC_GETSTATUS:
        270. caseWDIOC_GETBOOTSTATUS:
        271. returnput_user(0,p);
        272. caseWDIOC_KEEPALIVE:
        273. s3c2410wdt_keepalive();
        274. return0;
        275. caseWDIOC_SETTIMEOUT:
        276. if(get_user(new_margin,p))
        277. return-EFAULT;
        278. if(s3c2410wdt_set_heartbeat(new_margin))
        279. return-EINVAL;
        280. s3c2410wdt_keepalive();
        281. returnput_user(tmr_margin,p);
        282. caseWDIOC_GETTIMEOUT:
        283. returnput_user(tmr_margin,p);
        284. default:
        285. return-ENOTTY;
        286. }
        287. }
        289. /*kernelinterface*/
        291. //文件操作結構體
        292. staticconststructfile_operationss3c2410wdt_fops=
        293. {
        294. .owner=THIS_MODULE,
        295. .llseek=no_llseek,//屏蔽seek操作
        296. .write=s3c2410wdt_write,//寫方法
        297. .unlocked_ioctl=s3c2410wdt_ioctl,//控制方法
        298. .open=s3c2410wdt_open,//代開設備方法
        299. .release=s3c2410wdt_release,//關閉設備方法
        300. };
        302. staticstructmiscdevices3c2410wdt_miscdev=
        303. {
        304. .minor=WATCHDOG_MINOR,
        305. .name="watchdog",
        306. .fops=&s3c2410wdt_fops,
        307. };
        309. /*interrupthandlercode*/
        311. staticirqreturn_ts3c2410wdt_irq(intirqno,void*param)
        312. {
        313. //dev_info(wdt_dev,"watchdogtimerexpired(irq)n");
        314. s3c2410_gpio_setpin(S3C2410_GPB10,(count++)%2);
        315. s3c2410wdt_keepalive();
        316. returnIRQ_HANDLED;
        317. }
        318. /*deviceinterface*/
        320. //注冊設備時執行
        321. staticints3c2410wdt_probe(structplatform_device*pdev)
        322. {
        323. structresource*res;
        324. structdevice*dev;
        325. unsignedintwtcon;
        326. intstarted=0;
        327. intret;
        328. intsize;
        330. dev=&pdev->dev;
        331. wdt_dev=&pdev->dev;
        333. /*getthememoryregionforthewatchdogtimer*/
        334. //獲取IO端口資源，這里IORESOURCE_MEM和平臺設備中資源的定義一致
        335. res=platform_get_resource(pdev,IORESOURCE_MEM,0);
        336. if(res==NULL){
        337. dev_err(dev,"nomemoryresourcespecifiedn");
        338. return-ENOENT;
        339. }
        341. size=(res->end-res->start)+1;
        342. //申請內存空間
        343. wdt_mem=request_mem_region(res->start,size,pdev->name);
        344. if(wdt_mem==NULL){
        345. dev_err(dev,"failedtogetmemoryregionn");
        346. ret=-ENOENT;
        347. gotoerr_req;
        348. }
        349. //地址映射，wdt_base為基地址
        350. wdt_base=ioremap(res->start,size);
        351. if(wdt_base==NULL){
        352. dev_err(dev,"failedtoioremap()regionn");
        353. ret=-EINVAL;
        354. gotoerr_req;
        355. }
        357. DBG("probe:mappedwdt_base=%pn",wdt_base);
        358. //從平臺設備中獲取中斷號
        359. wdt_irq=platform_get_resource(pdev,IORESOURCE_IRQ,0);
        360. if(wdt_irq==NULL){
        361. dev_err(dev,"noirqresourcespecifiedn");
        362. ret=-ENOENT;
        363. gotoerr_map;
        364. }
        365. //注冊中斷，中斷處理函數s3c2410wdt_irq()
        366. ret=request_irq(wdt_irq->start,s3c2410wdt_irq,0,pdev->name,pdev);
        367. if(ret!=0){
        368. dev_err(dev,"failedtoinstallirq(%d)n",ret);
        369. gotoerr_map;
        370. }
        371. //獲取系統時鐘
        372. wdt_clock=clk_get(&pdev->dev,"watchdog");
        373. if(IS_ERR(wdt_clock)){
        374. dev_err(dev,"failedtofindwatchdogclocksourcen");
        375. ret=PTR_ERR(wdt_clock);
        376. gotoerr_irq;
        377. }
        378. //使能時鐘
        379. clk_enable(wdt_clock);
        381. /*seeifwecanactuallysettherequestedtimermargin,andif
        382. *not,trythedefaultvalue*/
        384. if(s3c2410wdt_set_heartbeat(tmr_margin))
        385. {//這里第一次設置計時周期為tmr_margin，如果設置不成功，則重新設置為默認值
        386. started=s3c2410wdt_set_heartbeat(
        387. CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME);
        389. if(started==0)
        390. dev_info(dev,
        391. "tmr_marginvalueoutofrange,default%dusedn",
        392. CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME);
        393. else
        394. dev_info(dev,"defaulttimervalueisoutofrange,cannotstartn");
        395. }
        396. //注冊設備
        397. ret=misc_register(&s3c2410wdt_miscdev);
        398. if(ret)
        399. {
        400. dev_err(dev,"cannotregistermiscdevonminor=%d(%d)n",
        401. WATCHDOG_MINOR,ret);
        402. gotoerr_clk;
        403. }
        405. if(tmr_atboot&&started==0)
        406. {
        407. dev_info(dev,"startingwatchdogtimern");
        408. s3c2410wdt_start();//啟動看門狗
        409. }
        410. elseif(!tmr_atboot)
        411. {
        412. /*ifwerenotenablingthewatchdog,thenensureitis
        413. *disabledifithasbeenleftrunningfromthebootloader
        414. *orothersource*/
        415. s3c2410wdt_stop();
        416. }
        418. /*printoutastatementofreadiness*/
        420. wtcon=readl(wdt_base+S3C2410_WTCON);
        422. dev_info(dev,"watchdog%sactive,reset%sabled,irq%sabledn",
        423. (wtcon&S3C2410_WTCON_ENABLE)?"":"in",
        424. (wtcon&S3C2410_WTCON_RSTEN)?"":"dis",
        425. (wtcon&S3C2410_WTCON_INTEN)?"":"en");
        426. //設置GPB10端口為輸出端口，用于點亮LED10
        427. s3c2410_gpio_cfgpin(S3C2410_GPB10,S3C2410_GPB10_OUTP);
        428. return0;
        430. //出錯跳轉表，異常處理
        432. err_clk:
        433. clk_disable(wdt_clock);
        434. clk_put(wdt_clock);
        436. err_irq:
        437. free_irq(wdt_irq->start,pdev);
        439. err_map:
        440. iounmap(wdt_base);
        442. err_req:
        443. release_resource(wdt_mem);
        444. kfree(wdt_mem);
        446. returnret;
        447. }
        449. //設備移除函數，釋放資源和映射
        450. staticints3c2410wdt_remove(structplatform_device*dev)
        451. {
        452. release_resource(wdt_mem);
        453. kfree(wdt_mem);
        454. wdt_mem=NULL;
        456. free_irq(wdt_irq->start,dev);
        457. wdt_irq=NULL;
        459. clk_disable(wdt_clock);
        460. clk_put(wdt_clock);
        461. wdt_clock=NULL;
        463. iounmap(wdt_base);
        464. misc_deregister(&s3c2410wdt_miscdev);
        465. return0;
        466. }
        468. //關閉看門狗
        469. staticvoids3c2410wdt_shutdown(structplatform_device*dev)
        470. {
        471. s3c2410wdt_stop();
        472. }
        474. //定義平臺設備驅動
        475. staticstructplatform_drivers3c2410wdt_driver={
        476. .probe=s3c2410wdt_probe,
        477. .remove=s3c2410wdt_remove,
        478. .shutdown=s3c2410wdt_shutdown,
        479. .driver={
        480. .owner=THIS_MODULE,
        481. .name="s3c2410-wdt",//該名稱參照內核源碼中該資源的名稱，兩者必須一致
        482. },
        483. };
        486. staticcharbanner[]__initdata=
        487. KERN_INFO"S3C2410WatchdogTimer,(c)2004SimtecElectronicsn";
        489. //驅動安裝時執行
        490. staticint__initwatchdog_init(void)
        491. {
        492. printk(banner);
        493. returnplatform_driver_register(&s3c2410wdt_driver);//注冊設備
        494. }
        496. //驅動移除是執行
        497. staticvoid__exitwatchdog_exit(void)
        498. {
        499. platform_driver_unregister(&s3c2410wdt_driver);//移除設備
        500. }
        502. module_init(watchdog_init);
        503. module_exit(watchdog_exit);
        505. MODULE_AUTHOR("YanMing");
        506. MODULE_DESCRIPTION("S3C2410WatchdogDeviceDriver");
        507. MODULE_LICENSE("GPL");
        508. MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

        設置默認不是重啟機器，而是執行中斷函數，當不喂狗，計數器減到0，點亮LED，然后喂狗，重新計數。				           
				
            
                
			
							
        
                
			              
              
            
        
		
        
		
        
		
        
		
        
		
        
			
          
				
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马龙县|
时尚|
乌什县|
平顺县|
屏东县|
宁夏|