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2 WDT 测试情况2.1硬件关闭WDT的情况下测试WDT 系统启动后，运行bsp里wdt_demo程序后，当不喂狗时系统死机但没有触发重启。 /usr # ./wdt_demo Open watchdog0 ok ii = 10 ii = 9 ii = 8 ii = 7 ii = 6 ii = 5 ii = 4 ii = 3 ii = 2 ii = 1 ii = 0 watchdog watchdog0: nowayout prevents watchdog being stopped! watchdog watchdog0: watchdog did not stop! 这说明通过软件无法打开nuc970的WDT 2.2硬件打开WDT的情况下测试WDT在这种情况下，默认的bsp中u-boot是有喂狗程序的，但引导linux时就没有喂狗程序了，如果linux系统启动时间过长，就会出现系统没启动完就复位的问题。系统启动时间短的是有机会进入系统的，但进入系统如果不立即喂狗就会重启。 ohci_hcd: USB 1.1 ‘Open’ Host Controller (OHCI) Driver nuc970-ohci nuc970-ohci: Nuvoton NUC970 OHCI Host Controller nuc970-ohci nuc970-ohci: new USB bus registered, assigned bus number 2 nuc970-ohci nuc970-ohci: irq 24, io mem 0xb0007000 hub 2-0:1.0: USB hub found hub 2-0:1.0: 2 ports detected usbcore: registered new interface driver usb-storage TCP: cubic registered NET: Registered protocol family 17 Freeing unused kernel memory: 10844K (c033b000 – c0dd2000) BusyBox v1.22.1 (2017-05-19 16:49:44 CST) built-in shell (ash) Enter ‘help’ for a list of built-in commands. ~ # NUC970 IBR 20151008.1735 No Key Boottttttæ“{kæ44aÃÿand_boot U-Boot 2013.04-rc2 (Nov 25 2015 – 13:25:12) CPU: NUC972 DRAM: 64 MiB NAND: 128 MiB MMC: mmc: 0, mmc: 1 In: serial Out: serial Err: serial Net: emac Hit any key to stop autoboot: 0 Using emac device TFTP from server 10.130.11.18; our IP address is 10.130.11.120 Filename ‘970uimage’. Load address: 0x7fc0 在这种情况，系统启动后就运行wdt_demo程序是可以控制WDT正常工作的：正常喂狗时系统正常工作，不喂狗时WDT复位。 NET: Registered protocol family 17 Freeing unused kernel memory: 10844K (c033b000 – c0dd2000) BusyBox v1.22.1 (2017-05-19 16:49:44 CST) built-in shell (ash) Enter ‘help’ for a list of built-in commands. Open watchdog0 ok ii = 10 ii = 9 ii = 8 ii = 7 ii = 6 ii = 5 ii = 4 ii = 3 ii = 2 ii = 1 ii = 0 watchdog watchdog0: nowayout prevents watchdog being stopped! watchdog watchdog0: watchdog did not stop! ~ # NUC970 IBR 20151008.1735 No Key Boottttttæ“{kæ44aÃÿand_boot U-Boot 2013.04-rc2 (Nov 25 2015 – 13:25:12) CPU: NUC972 DRAM: 64 MiB NAND: 128 MiB MMC: mmc: 0, mmc: 1 In: serial Out: serial Err: serial Net: emac 不配置内核Disable watchdog shutdown on close时，当wdt_demo运行结束退出后，linux系统会关闭wdt。 Device drivers—> Watchdog Timer Support—>[ ] Disable watchdog shutdown on close 测试结果如下： hub 2-0:1.0: 2 ports detected usbcore: registered new interface driver usb-storage TCP: cubic registered NET: Registered protocol family 17 Freeing unused kernel memory: 10844K (c033b000 – c0dd2000) BusyBox v1.22.1 (2017-05-19 16:49:44 CST) built-in shell (ash) Enter ‘help’ for a list of built-in commands. Open watchdog0 ok ii = 10 ii = 9 ii = 8 ii = 7 ii = 6 ii = 5 ii = 4 ii = 3 ii = 2 ii = 1 ii = 0 Stopping WDT is probably not a good idea 系统没有重启，表明linux系统可以通过软件关闭nuc970的WDT。 通过软件关闭WDT后，还能否通过软件来开启WDT呢？ 修改Wdt_demo程序在程序喂狗结束后不退出程序，加入一个死循环程序 While(1){} 编译demo程序并保存为wdt_demo1 TCP: cubic registered NET: Registered protocol family 17 Freeing unused kernel memory: 10884K (c033b000 – c0ddc000) BusyBox v1.22.1 (2017-05-19 16:49:44 CST) built-in shell (ash) Enter ‘help’ for a list of built-in commands. Open watchdog0 ok ii = 10 ii = 9 ii = 8 ii = 7 ii = 6 ii = 5 ii = 4 ii = 3 ii = 2 ii = 1 ii = 0 Stopping WDT is probably not a good idea ~ # ~ # ~ # ~ # /usr # ./wdt_demo1 Open watchdog0 ok ii = 10 ii = 9 ii = 8 ii = 7 ii = 6 ii = 5 ii = 4 ii = 3 ii = 2 ii = 1 ii = 0 NUC970 IBR 20151008.1735 No Key Boottttttæ“{kæ44aÃÿand_boot U-Boot 2013.04-rc2 (Nov 25 2015 – 13:25:12) CPU: NUC972 DRAM: 64 MiB NAND: 128 MiB MMC: mmc: 0, mmc: 1 In: serial Out: serial Err: serial Net: emac Hit any key to stop autoboot: 0 Using emac device TFTP from server 10.130.11.18; our IP address is 10.130.11.120 Filename ‘970uimage’. Load address: 0x7fc0 以上测试表明，nuc970的WDT虽然只能由硬件来打开，但硬件打开后，软件就可以正常控制WDT的打开与关闭。 2.3 在硬件打开WDT的情况下，U-BOOT下如何关闭WDT默认情况下硬件打开WDT后，u-boot是不会关闭WDT的，客户正常使用WDT时希望进入linux系统后再打开WDT。如何在U-boot下关闭WDT呢？ 上面测试表明，硬件打开WDT后，是可以通过软件来控制WDT的开关的。所以只要在u-boot的WDT驱动中关闭通过软件关闭WDT即可。 打开wdt的驱动文件，分析发现nuc970的wdt驱动中预留了通过环境变量watchdog来控制WDT的开关的方法。 设置环境变量watchdog=off时，u-boot就关闭WDT。不设置环境变量watchog或设置为其他值，就不关闭WDT。 在u-boot下通过如下命令设置watchog环境变量。 U-Boot>set watchdog off U-Boot>save 设置好以后，重启系统： NET: Registered protocol family 17 Freeing unused kernel memory: 10884K (c033b000 – c0ddc000) BusyBox v1.22.1 (2017-05-19 16:49:44 CST) built-in shell (ash) Enter ‘help’ for a list of built-in commands. ~ # 工作正常，进入系统后不重启，表明WDT已经关闭。
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你好，请指导一下，请问什么是硬件打开WDT？ 我直接用的linux的wdt_demo，看门狗在死循环超时后，直接死机，没有进行复位，是因为我没有硬件打开WDT的原因吗？这个硬件打开怎么操作？