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	 > 嵌入式系統(tǒng) > 設(shè)計應(yīng)用 > ARM-Linux驅(qū)動--Watch Dog Timer(看門狗)驅(qū)動分析
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          ARM-Linux驅(qū)動--Watch Dog Timer(看門狗)驅(qū)動分析
          
						
          
				作者：
				時間：2016-11-20
				來源：網(wǎng)絡(luò)
				
				
				
				
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			硬件平臺：FL2440
          內(nèi)核版本：2.6.28
          本文引用地址：http://www.ex-cimer.com/article/201611/318869.htm
          主機平臺：Ubuntu 11,04
          內(nèi)核版本：2.6.39
          1、看門狗驅(qū)動的原理
          下圖是看門狗驅(qū)動的原理圖
          可以看出，PCLK是系統(tǒng)時鐘，經(jīng)過8位的預(yù)分頻，然后再被分頻（16、32、64、128）然后產(chǎn)生計數(shù)脈沖，進行計數(shù)，當(dāng)計數(shù)器WTCNT加到0或減到0，然后產(chǎn)生中斷，或引起系統(tǒng)復(fù)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(qū)動分析
          下面是自己的驅(qū)動分析，如有理解錯誤，請指正
          注，為了盡量是驅(qū)動容易理解，這個驅(qū)動暫時將有關(guān)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(shè)置默認為執(zhí)行中斷
          33. staticintdebug;
          34. staticintcount;//用于計數(shù)，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(nèi)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(jīng)過ioremap后的內(nèi)存基地址
          66. staticunsignedintwdt_count;//保存向WTCNT寫的計數(shù)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(shù)，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(shè)備看門狗使能無效、復(fù)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(shù)因子128
          115. if(soft_noboot)//使用參數(shù)soft_noboot來選擇看門狗到時是重啟還是執(zhí)行中斷函數(shù)
          116. {
          117. wtcon|=S3C2410_WTCON_INTEN;//中斷使能
          118. wtcon&=~S3C2410_WTCON_RSTEN;//復(fù)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(fù)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(shè)置WTCON
          129. spin_unlock(&wdt_lock);
          130. }
          132. //設(shè)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(dāng)加大預(yù)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(yù)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(shè)置預(yù)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(shè)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(shù)據(jù)
          237. return-EFAULT;
          238. if(c==V)//當(dāng)輸入V時，關(guān)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(shè)置成CLOSE_STATE_ALLOW后，當(dāng)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(shù)
          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(jié)構(gòu)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(shè)備方法
          299. .release=s3c2410wdt_release,//關(guān)閉設(shè)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(shè)備時執(zhí)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(shè)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(nèi)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(shè)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(shù)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(tǒng)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(shè)置計時周期為tmr_margin，如果設(shè)置不成功，則重新設(shè)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(shè)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(shè)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(zhuǎn)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(shè)備移除函數(shù)，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(guān)閉看門狗
          469. staticvoids3c2410wdt_shutdown(structplatform_device*dev)
          470. {
          471. s3c2410wdt_stop();
          472. }
          474. //定義平臺設(shè)備驅(qū)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(nèi)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(qū)動安裝時執(zhí)行
          490. staticint__initwatchdog_init(void)
          491. {
          492. printk(banner);
          493. returnplatform_driver_register(&s3c2410wdt_driver);//注冊設(shè)備
          494. }
          496. //驅(qū)動移除是執(zhí)行
          497. staticvoid__exitwatchdog_exit(void)
          498. {
          499. platform_driver_unregister(&s3c2410wdt_driver);//移除設(shè)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(shè)置默認不是重啟機器，而是執(zhí)行中斷函數(shù)，當(dāng)不喂狗，計數(shù)器減到0，點亮LED，然后喂狗，重新計數(shù)。				             
				
            
                
			
							
          
                
			              
              
            
          
		
          
		
          
		
          
		
          
		
          
			
            
				
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