Ubuntu内核打开硬件watchdog

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前言

最近在部署linux系统的时候发现一个问题，kernel出现超时未响应。瞬间一万只草泥马奔腾，我心想内核这么强大的东西出现bug也能被我撞到，不管你信不信内核不是万能的，只要是人写的东西就有bug。所以我经过刻苦钻研终于成功打开了watchdog，而且是硬件的watchdog。本文使用的设备是firefl的aio-rk3399c，其他的设备可以参考我的方法，并结合一些钻研精神。

关于怎么打开软件watchdog请参考我的另一篇文章linux watchdog配置

这两篇文章结合可以完成硬件watchdog和软件watchdog的结合使用，关键时刻有奇效。

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一、watchdog是什么？

虽然看到这篇文章的人肯定已经知道是什么了，但是这里我还是要赘述下，给不知道的人看。

1.硬件看门狗

看门狗，又叫 watchdog，从本质上来说就是一个定时器电路，一般有一个输入和一个输出，其中输入叫做喂狗，输出一般连接到另外一个部分的复位端，一般是连接到单片机。 看门狗的功能是定期的查看芯片内部的情况，一旦发生错误就向芯片发出重启信号。看门狗命令在程序的中断中拥有最高的优先级。

解释下：硬件看门狗集成在SOC里，通过驱动让它工作，理论上除非掉电或者电路物理损坏，绝不会出现失败的可能，所以这个是最后一道屏障。

2.软件件看门狗

这里说两种，一种是集成在内核的module名字叫soft_watchdog，还有一种是linux纯软件实现的watchdog，本质上是一个daemon。前者要使用的话需要在内核编译的时候打开才行，后者直接在文件系统里安装就行了。差别我没有测出来，我觉的是权限和保活，前者作为内核的module稳定性肯定不必要多说了，后者是上层软件稳定性有待观察。今天我们不需要它太稳定，因为我们有办法解决这些问题。

二、编译内核

因为各硬件之间的差异太大，这里我的教程以firefly的aio-rk3399c来作为示例，默认你已经从官方下载了源代码（firefly是开源的），如果你有对接人的话你可以直接跟他说让他帮你打开watchdog，这样你就不需要自己操作了。

1.添加配置

先进入源代码目录，正常的firefly的源代码目录应该是下面这样。

husz@insigma:/data/users/husz/rk3399_linux_release_v2.5.1_20210301$ ls
app  buildroot  build.sh  debian  device  distro  docs  envsetup.sh  external  kernel  Makefile  mkfirmware.sh  prebuilts  rkbin  rkflash.sh  rockdev  tools  u-boot  ubuntu_rootfs  yocto

我们所有的操作都是基于build.sh这个脚本来的。

我们需要操作的两个文件是：
内核配置文件
kernel/arch/arm64/configs/firefly_linux_defconfig
配置有点多，这些配置就是内核需要打开的功能。

# CONFIG_LOCALVERSION_AUTO is not set
CONFIG_DEFAULT_HOSTNAME="localhost"
CONFIG_SYSVIPC=y
CONFIG_POSIX_MQUEUE=y
CONFIG_FHANDLE=y
CONFIG_AUDIT=y
CONFIG_AUDITSYSCALL=y
CONFIG_NO_HZ=y
CONFIG_HIGH_RES_TIMERS=y
CONFIG_LOG_BUF_SHIFT=18
CONFIG_CGROUPS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_PIDS=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CPUSETS=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_MEMCG=y
CONFIG_MEMCG_SWAP=y
CONFIG_MEMCG_KMEM=y
CONFIG_CGROUP_HUGETLB=y
CONFIG_CGROUP_PERF=y
CONFIG_CGROUP_SCHED=y
CONFIG_CFS_BANDWIDTH=y
CONFIG_RT_GROUP_SCHED=y
CONFIG_BLK_CGROUP=y
CONFIG_NAMESPACES=y
CONFIG_USER_NS=y
CONFIG_DEFAULT_USE_ENERGY_AWARE=y
CONFIG_BLK_DEV_INITRD=y
CONFIG_CC_OPTIMIZE_FOR_SIZE=y
CONFIG_EMBEDDED=y
# CONFIG_COMPAT_BRK is not set
CONFIG_PROFILING=y
CONFIG_MODULES=y
CONFIG_MODULE_FORCE_LOAD=y
CONFIG_MODULE_UNLOAD=y
CONFIG_MODULE_FORCE_UNLOAD=y
CONFIG_BLK_DEV_THROTTLING=y
CONFIG_PARTITION_ADVANCED=y
CONFIG_CFQ_GROUP_IOSCHED=y
CONFIG_ARCH_ROCKCHIP=y
CONFIG_PCI=y
CONFIG_PCI_MSI=y
CONFIG_ROCKCHIP_PCIE_DMA_OBJ=y
CONFIG_PCIE_ROCKCHIP=y
CONFIG_PCIEPORTBUS=y
# CONFIG_PCIEASPM is not set
# CONFIG_ARM64_ERRATUM_826319 is not set
# CONFIG_ARM64_ERRATUM_827319 is not set
# CONFIG_ARM64_ERRATUM_824069 is not set
# CONFIG_ARM64_ERRATUM_819472 is not set
# CONFIG_ARM64_ERRATUM_832075 is not set
# CONFIG_CAVIUM_ERRATUM_22375 is not set
# CONFIG_CAVIUM_ERRATUM_23154 is not set
CONFIG_SCHED_MC=y
CONFIG_NR_CPUS=8
CONFIG_PREEMPT_VOLUNTARY=y
CONFIG_HZ_1000=y
# CONFIG_COMPACTION is not set
CONFIG_DEFAULT_MMAP_MIN_ADDR=32768
CONFIG_ZSMALLOC=y
CONFIG_SECCOMP=y
CONFIG_ARMV8_DEPRECATED=y
CONFIG_SWP_EMULATION=y
CONFIG_CP15_BARRIER_EMULATION=y
CONFIG_SETEND_EMULATION=y
# CONFIG_EFI is not set
CONFIG_COMPAT=y
CONFIG_PM_DEBUG=y
CONFIG_PM_ADVANCED_DEBUG=y
CONFIG_WQ_POWER_EFFICIENT_DEFAULT=y
CONFIG_CPU_IDLE=y
CONFIG_ARM_CPUIDLE=y
CONFIG_CPU_FREQ=y
CONFIG_CPU_FREQ_DEFAULT_GOV_INTERACTIVE=y
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_POWERSAVE=y
CONFIG_CPU_FREQ_GOV_USERSPACE=y
CONFIG_CPU_FREQ_GOV_ONDEMAND=y
CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
CONFIG_CPUFREQ_DT=y
CONFIG_ARM_ROCKCHIP_CPUFREQ=y
CONFIG_NET=y
CONFIG_PACKET=y
CONFIG_UNIX=y
CONFIG_XFRM_USER=y
CONFIG_XFRM_STATISTICS=y
CONFIG_NET_KEY=y
CONFIG_INET=y
CONFIG_IP_MULTICAST=y
CONFIG_IP_ADVANCED_ROUTER=y
CONFIG_IP_FIB_TRIE_STATS=y
CONFIG_IP_MULTIPLE_TABLES=y
CONFIG_IP_ROUTE_MULTIPATH=y
CONFIG_IP_ROUTE_VERBOSE=y
CONFIG_NET_IPGRE_BROADCAST=y
CONFIG_IP_MROUTE=y
CONFIG_IP_PIMSM_V1=y
CONFIG_IP_PIMSM_V2=y
CONFIG_NET_FOU_IP_TUNNELS=y
CONFIG_INET_ESP=y
CONFIG_SYN_COOKIES=y
# CONFIG_INET_XFRM_MODE_TUNNEL is not set
# CONFIG_INET_XFRM_MODE_BEET is not set
# CONFIG_INET_LRO is not set
# CONFIG_INET_DIAG is not set
# CONFIG_INET6_XFRM_MODE_TRANSPORT is not set
# CONFIG_INET6_XFRM_MODE_TUNNEL is not set
# CONFIG_INET6_XFRM_MODE_BEET is not set
# CONFIG_IPV6_SIT is not set
# CONFIG_ANDROID_PARANOID_NETWORK is not set
CONFIG_TCP_CONG_ADVANCED=y
CONFIG_TCP_MD5SIG=y
CONFIG_IPV6_ROUTER_PREF=y
CONFIG_IPV6_ROUTE_INFO=y
CONFIG_IPV6_SIT_6RD=y
CONFIG_IPV6_MULTIPLE_TABLES=y
CONFIG_IPV6_SUBTREES=y
CONFIG_IPV6_MROUTE=y
CONFIG_IPV6_MROUTE_MULTIPLE_TABLES=y
CONFIG_IPV6_PIMSM_V2=y
CONFIG_NETLABEL=y
CONFIG_NETWORK_SECMARK=y
CONFIG_NETFILTER=y
CONFIG_NF_CONNTRACK=y
CONFIG_NF_CONNTRACK_SECMARK=y
CONFIG_NF_CONNTRACK_ZONES=y
# CONFIG_NF_CONNTRACK_PROCFS is not set
CONFIG_NF_CONNTRACK_EVENTS=y
CONFIG_NF_CONNTRACK_TIMEOUT=y
CONFIG_NF_CONNTRACK_TIMESTAMP=y
CONFIG_NF_CONNTRACK_FTP=y
CONFIG_NF_CONNTRACK_TFTP=y
CONFIG_NETFILTER_NETLINK_GLUE_CT=y
CONFIG_NETFILTER_XT_MATCH_ADDRTYPE=y
CONFIG_NETFILTER_XT_MATCH_CONNTRACK=y
CONFIG_NETFILTER_XT_MATCH_IPVS=y
CONFIG_IP_VS=y
CONFIG_IP_VS_IPV6=y
CONFIG_BRIDGE_NETFILTER=y
CONFIG_IP_VS_PROTO_TCP=y
CONFIG_IP_VS_PROTO_UDP=y
CONFIG_IP_VS_PROTO_ESP=y
CONFIG_IP_VS_PROTO_AH=y
CONFIG_IP_VS_PROTO_SCTP=y
CONFIG_IP_VS_RR=y
CONFIG_IP_VS_NFCT=y
CONFIG_NF_CONNTRACK_IPV4=y
CONFIG_IP_NF_IPTABLES=y
CONFIG_IP_NF_FILTER=y
CONFIG_IP_NF_NAT=y
CONFIG_IP_NF_TARGET_MASQUERADE=y
CONFIG_IP_NF_TARGET_REDIRECT=y
# CONFIG_IP_DCCP_CCID3 is not set
CONFIG_SCTP_DEFAULT_COOKIE_HMAC_SHA1=y
CONFIG_SCTP_COOKIE_HMAC_MD5=y
CONFIG_L2TP_V3=y
CONFIG_BRIDGE=y
CONFIG_BRIDGE_VLAN_FILTERING=y
CONFIG_VLAN_8021Q_GVRP=y
CONFIG_VLAN_8021Q_MVRP=y
CONFIG_IPDDP_ENCAP=y
CONFIG_IEEE802154_NL802154_EXPERIMENTAL=y
CONFIG_NET_SCHED=y
CONFIG_CLS_U32_MARK=y
CONFIG_NET_EMATCH=y
CONFIG_NET_CLS_ACT=y
CONFIG_GACT_PROB=y
CONFIG_DCB=y
CONFIG_BATMAN_ADV_DAT=y
CONFIG_BATMAN_ADV_NC=y
CONFIG_BATMAN_ADV_MCAST=y
CONFIG_NET_L3_MASTER_DEV=y
CONFIG_CGROUP_NET_PRIO=y
CONFIG_BPF_JIT=y
CONFIG_BT=y
CONFIG_BT_RFCOMM=y
CONFIG_BT_HIDP=y
CONFIG_BT_HCIBTUSB=y
CONFIG_BT_HCIUART=y
CONFIG_BT_HCIUART_ATH3K=y
CONFIG_BT_HCIUART_LL=y
CONFIG_BT_HCIBFUSB=y
CONFIG_BT_HCIVHCI=y
CONFIG_BT_MRVL=y
CONFIG_BT_MRVL_SDIO=y
CONFIG_NL80211_TESTMODE=y
CONFIG_CFG80211_DEBUGFS=y
CONFIG_CFG80211_WEXT=y
CONFIG_MAC80211_LEDS=y
CONFIG_MAC80211_DEBUGFS=y
CONFIG_MAC80211_DEBUG_MENU=y
CONFIG_MAC80211_VERBOSE_DEBUG=y
CONFIG_RFKILL=y
CONFIG_NFC=y
CONFIG_NFC_DIGITAL=y
CONFIG_NFC_DL1825=y
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y
CONFIG_EXTRA_FIRMWARE="rtl8723du_config rtl8723du_fw"
CONFIG_DEBUG_DEVRES=y
CONFIG_CONNECTOR=y
CONFIG_MTD=y
CONFIG_MTD_M25P80=y
CONFIG_MTD_SPI_NOR=y
CONFIG_ZRAM=y
CONFIG_BLK_DEV_LOOP=y
CONFIG_BLK_DEV_RAM=y
CONFIG_BLK_DEV_RAM_COUNT=1
CONFIG_BLK_DEV_NVME=y
CONFIG_ROCKCHIP_SCR=y
CONFIG_SRAM=y
CONFIG_DS18B20=y
CONFIG_BLK_DEV_SD=y
CONFIG_BLK_DEV_SR=y
CONFIG_CHR_DEV_SG=y
CONFIG_SCSI_SCAN_ASYNC=y
CONFIG_SCSI_SPI_ATTRS=y
CONFIG_ATA=y
CONFIG_SATA_AHCI=y
CONFIG_SATA_AHCI_PLATFORM=y
CONFIG_AHCI_CEVA=y
CONFIG_ATA_GENERIC=y
CONFIG_MD=y
CONFIG_BLK_DEV_DM=y
CONFIG_DM_THIN_PROVISIONING=y
CONFIG_NETDEVICES=y
CONFIG_DUMMY=y
CONFIG_MACVLAN=y
CONFIG_IPVLAN=y
CONFIG_VXLAN=y
CONFIG_TUN=y
CONFIG_VETH=y
# CONFIG_NET_VENDOR_3COM is not set
# CONFIG_NET_VENDOR_ADAPTEC is not set
# CONFIG_NET_VENDOR_AGERE is not set
# CONFIG_NET_VENDOR_ALTEON is not set
# CONFIG_NET_VENDOR_AMD is not set
# CONFIG_NET_VENDOR_ARC is not set
# CONFIG_NET_VENDOR_ATHEROS is not set
# CONFIG_NET_CADENCE is not set
# CONFIG_NET_VENDOR_BROADCOM is not set
# CONFIG_NET_VENDOR_BROCADE is not set
# CONFIG_NET_VENDOR_CAVIUM is not set
# CONFIG_NET_VENDOR_CHELSIO is not set
# CONFIG_NET_VENDOR_CISCO is not set
# CONFIG_NET_VENDOR_DEC is not set
# CONFIG_NET_VENDOR_DLINK is not set
# CONFIG_NET_VENDOR_EMULEX is not set
# CONFIG_NET_VENDOR_EZCHIP is not set
# CONFIG_NET_VENDOR_EXAR is not set
# CONFIG_NET_VENDOR_HISILICON is not set
# CONFIG_NET_VENDOR_HP is not set
# CONFIG_NET_VENDOR_INTEL is not set
# CONFIG_NET_VENDOR_MARVELL is not set
# CONFIG_NET_VENDOR_MELLANOX is not set
# CONFIG_NET_VENDOR_MICREL is not set
# CONFIG_NET_VENDOR_MICROCHIP is not set
# CONFIG_NET_VENDOR_MYRI is not set
# CONFIG_NET_VENDOR_NATSEMI is not set
# CONFIG_NET_VENDOR_NVIDIA is not set
# CONFIG_NET_VENDOR_OKI is not set
# CONFIG_NET_PACKET_ENGINE is not set
# CONFIG_NET_VENDOR_QLOGIC is not set
# CONFIG_NET_VENDOR_QUALCOMM is not set
# CONFIG_NET_VENDOR_REALTEK is not set
# CONFIG_NET_VENDOR_RENESAS is not set
# CONFIG_NET_VENDOR_RDC is not set
# CONFIG_NET_VENDOR_ROCKER is not set
# CONFIG_NET_VENDOR_SAMSUNG is not set
# CONFIG_NET_VENDOR_SEEQ is not set
# CONFIG_NET_VENDOR_SILAN is not set
# CONFIG_NET_VENDOR_SIS is not set
# CONFIG_NET_VENDOR_SMSC is not set
CONFIG_STMMAC_ETH=y
# CONFIG_NET_VENDOR_SUN is not set
# CONFIG_NET_VENDOR_SYNOPSYS is not set
# CONFIG_NET_VENDOR_TEHUTI is not set
# CONFIG_NET_VENDOR_TI is not set
# CONFIG_NET_VENDOR_VIA is not set
# CONFIG_NET_VENDOR_WIZNET is not set
CONFIG_ROCKCHIP_PHY=y
CONFIG_USB_RTL8150=y
CONFIG_USB_RTL8152=y
CONFIG_USB_NET_CDC_MBIM=y
# CONFIG_USB_NET_NET1080 is not set
# CONFIG_USB_NET_CDC_SUBSET is not set
# CONFIG_USB_NET_ZAURUS is not set
CONFIG_USB_NET_QMI_WWAN=y
CONFIG_LIBERTAS_THINFIRM=y
CONFIG_USB_NET_RNDIS_WLAN=y
CONFIG_WL_MEDIATEK=y
CONFIG_MT7601U=y
CONFIG_RTL8192CU=y
CONFIG_WL_ROCKCHIP=y
CONFIG_WIFI_LOAD_DRIVER_WHEN_KERNEL_BOOTUP=y
CONFIG_AP6XXX=y
CONFIG_RTL8723DU=y
CONFIG_MWIFIEX=y
CONFIG_MWIFIEX_SDIO=y
CONFIG_INPUT_FF_MEMLESS=y
# CONFIG_INPUT_MOUSEDEV is not set
CONFIG_INPUT_EVDEV=y
CONFIG_KEYBOARD_ADC=y
# CONFIG_KEYBOARD_ATKBD is not set
CONFIG_KEYBOARD_GPIO=y
CONFIG_KEYBOARD_GPIO_POLLED=y
CONFIG_KEYBOARD_ROCKCHIP=y
CONFIG_KEYBOARD_CROS_EC=y
# CONFIG_MOUSE_PS2 is not set
CONFIG_MOUSE_CYAPA=y
CONFIG_MOUSE_ELAN_I2C=y
CONFIG_INPUT_TOUCHSCREEN=y
CONFIG_TOUCHSCREEN_ATMEL_MXT=y
CONFIG_TOUCHSCREEN_GSLX680_FIREFLY=y
CONFIG_TOUCHSCREEN_GSL3673=y
CONFIG_TOUCHSCREEN_GT9XX=y
CONFIG_TOUCHSCREEN_ELAN=y
CONFIG_TOUCHSCREEN_USB_COMPOSITE=y
CONFIG_TOUCHSCREEN_GT1X=y
CONFIG_TOUCHSCREEN_HX83102=y
CONFIG_ROCKCHIP_REMOTECTL=y
CONFIG_ROCKCHIP_REMOTECTL_PWM=y
CONFIG_RK_IR_NO_DEEP_SLEEP=y
CONFIG_SENSOR_DEVICE=y
CONFIG_GS_MC3230=y
CONFIG_INPUT_MISC=y
CONFIG_INPUT_RK8XX_PWRKEY=y
CONFIG_INPUT_UINPUT=y
CONFIG_INPUT_GPIO=y
# CONFIG_SERIO is not set
CONFIG_DEVPTS_MULTIPLE_INSTANCES=y
# CONFIG_LEGACY_PTYS is not set
# CONFIG_DEVKMEM is not set
CONFIG_SERIAL_8250=y
CONFIG_SERIAL_8250_CONSOLE=y
# CONFIG_SERIAL_8250_PCI is not set
CONFIG_SERIAL_8250_NR_UARTS=5
CONFIG_SERIAL_8250_RUNTIME_UARTS=5
CONFIG_SERIAL_8250_DW=y
CONFIG_SERIAL_OF_PLATFORM=y
CONFIG_HW_RANDOM=y
CONFIG_HW_RANDOM_ROCKCHIP=y
CONFIG_TCG_TPM=y
CONFIG_TCG_TIS_I2C_INFINEON=y
CONFIG_I2C_CHARDEV=y
CONFIG_I2C_MUX=y
CONFIG_I2C_RK3X=y
CONFIG_I2C_CROS_EC_TUNNEL=y
CONFIG_SPI=y
CONFIG_SPI_BITBANG=y
CONFIG_SPI_ROCKCHIP=y
CONFIG_SPI_SPIDEV=y
CONFIG_SPI_WK2XXX=y
CONFIG_DEBUG_GPIO=y
CONFIG_GPIO_SYSFS=y
CONFIG_GPIO_GENERIC_PLATFORM=y
CONFIG_GPIO_PCA953X=y
CONFIG_GPIO_RK8XX=y
CONFIG_GPIO_WIEGAND_SEND=y
CONFIG_GPIO_WIEGAND_RECEIVE=y
CONFIG_GPIO_RADAR=y
CONFIG_GPIO_ADB_SELECT=y
CONFIG_BATTERY_SBS=y
CONFIG_CHARGER_GPIO=y
CONFIG_CHARGER_BQ24735=y
CONFIG_BATTERY_CW2015=y
CONFIG_BATTERY_RK817=y
CONFIG_CHARGER_RK817=y
CONFIG_POWER_RESET_GPIO=y
CONFIG_POWER_RESET_GPIO_RESTART=y
CONFIG_SYSCON_REBOOT_MODE=y
CONFIG_POWER_AVS=y
CONFIG_ROCKCHIP_IODOMAIN=y
CONFIG_SENSORS_NTC_THERMISTOR=y
CONFIG_THERMAL=y
CONFIG_THERMAL_WRITABLE_TRIPS=y
CONFIG_THERMAL_DEFAULT_GOV_POWER_ALLOCATOR=y
CONFIG_THERMAL_GOV_FAIR_SHARE=y
CONFIG_THERMAL_GOV_STEP_WISE=y
CONFIG_CPU_THERMAL=y
CONFIG_DEVFREQ_THERMAL=y
CONFIG_ROCKCHIP_THERMAL=y
CONFIG_WATCHDOG=y
CONFIG_DW_WATCHDOG=y
CONFIG_SOFT_WATCHDOG=n
CONFIG_WATCHDOG_CORE=y
CONFIG_MFD_CROS_EC=y
CONFIG_MFD_CROS_EC_SPI=y
CONFIG_MFD_RK808=y
CONFIG_MFD_TPS6586X=y
CONFIG_FUSB_30X=y
CONFIG_REGULATOR=y
CONFIG_REGULATOR_DEBUG=y
CONFIG_REGULATOR_FIXED_VOLTAGE=y
CONFIG_REGULATOR_ACT8865=y
CONFIG_REGULATOR_FAN53555=y
CONFIG_REGULATOR_GPIO=y
CONFIG_REGULATOR_LP8752=y
CONFIG_REGULATOR_MP8865=y
CONFIG_REGULATOR_MP8859=y
CONFIG_REGULATOR_PWM=y
CONFIG_REGULATOR_RK808=y
CONFIG_REGULATOR_RK818=y
CONFIG_REGULATOR_TPS6586X=y
CONFIG_REGULATOR_XZ3216=y
CONFIG_MEDIA_SUPPORT=y
CONFIG_MEDIA_CAMERA_SUPPORT=y
CONFIG_MEDIA_RC_SUPPORT=y
CONFIG_MEDIA_CEC_SUPPORT=y
CONFIG_MEDIA_CONTROLLER=y
CONFIG_VIDEO_V4L2_SUBDEV_API=y
# CONFIG_IR_RC5_DECODER is not set
# CONFIG_IR_RC6_DECODER is not set
# CONFIG_IR_JVC_DECODER is not set
# CONFIG_IR_SONY_DECODER is not set
# CONFIG_IR_SANYO_DECODER is not set
# CONFIG_IR_SHARP_DECODER is not set
# CONFIG_IR_MCE_KBD_DECODER is not set
# CONFIG_IR_XMP_DECODER is not set
CONFIG_MEDIA_USB_SUPPORT=y
CONFIG_USB_VIDEO_CLASS=y
# CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV is not set
# CONFIG_USB_GSPCA is not set
CONFIG_NPU_USB_ACM=y
CONFIG_V4L_PLATFORM_DRIVERS=y
CONFIG_SOC_CAMERA=y
CONFIG_VIDEO_ROCKCHIP_ISP1=y
CONFIG_VIDEO_ROCKCHIP_USBACM_CONTROL=y
CONFIG_V4L_MEM2MEM_DRIVERS=y
CONFIG_VIDEO_ROCKCHIP_RGA=y
# CONFIG_MEDIA_SUBDRV_AUTOSELECT is not set
# CONFIG_VIDEO_IR_I2C is not set
CONFIG_VIDEO_TC35874X=y
CONFIG_VIDEO_IMX327=y
CONFIG_VIDEO_OV4689=y
CONFIG_VIDEO_OV13850=y
CONFIG_VIDEO_VM149C=y
CONFIG_VIDEO_XC7022=y
CONFIG_VIDEO_XC7160=y
# CONFIG_DVB_AU8522_V4L is not set
# CONFIG_DVB_TUNER_DIB0070 is not set
# CONFIG_DVB_TUNER_DIB0090 is not set
# CONFIG_VGA_ARB is not set
CONFIG_DRM=y
CONFIG_DRM_LOAD_EDID_FIRMWARE=y
CONFIG_DRM_DMA_SYNC=y
CONFIG_DRM_ROCKCHIP=y
CONFIG_ROCKCHIP_DRM_DEBUG=y
CONFIG_ROCKCHIP_CDN_DP=y
CONFIG_ROCKCHIP_DW_HDMI=y
CONFIG_ROCKCHIP_DW_MIPI_DSI=y
CONFIG_ROCKCHIP_ANALOGIX_DP=y
CONFIG_ROCKCHIP_INNO_HDMI=y
CONFIG_ROCKCHIP_LVDS=y
CONFIG_ROCKCHIP_DRM_TVE=y
CONFIG_ROCKCHIP_RGB=y
CONFIG_DRM_PANEL_SIMPLE=y
CONFIG_DRM_DW_HDMI_I2S_AUDIO=y
CONFIG_DRM_DW_HDMI_CEC=y
CONFIG_MALI400=y
CONFIG_MALI450=y
# CONFIG_MALI400_PROFILING is not set
CONFIG_MALI_SHARED_INTERRUPTS=y
CONFIG_MALI_DT=y
CONFIG_MALI_DEVFREQ=y
CONFIG_MALI_MIDGARD=y
CONFIG_MALI_EXPERT=y
CONFIG_MALI_PLATFORM_THIRDPARTY=y
CONFIG_MALI_PLATFORM_THIRDPARTY_NAME="rk"
CONFIG_MALI_DEBUG=y
CONFIG_MALI_PWRSOFT_765=y
CONFIG_MALI_BIFROST_FOR_LINUX=y
CONFIG_BACKLIGHT_LCD_SUPPORT=y
# CONFIG_LCD_CLASS_DEVICE is not set
CONFIG_BACKLIGHT_CLASS_DEVICE=y
CONFIG_BACKLIGHT_PWM=y
CONFIG_ROCKCHIP_RGA2=y
CONFIG_RK_VCODEC=y
CONFIG_IEP=y
CONFIG_IEP_MMU=y
CONFIG_ROCKCHIP_MPP_SERVICE=y
CONFIG_ROCKCHIP_MPP_DEVICE=y
CONFIG_FRAMEBUFFER_CONSOLE=y
CONFIG_SOUND=y
CONFIG_SND=y
CONFIG_SND_SEQUENCER=y
CONFIG_SND_SEQ_DUMMY=y
CONFIG_SND_HRTIMER=y
CONFIG_SND_DYNAMIC_MINORS=y
# CONFIG_SND_SUPPORT_OLD_API is not set
# CONFIG_SND_PCI is not set
# CONFIG_SND_SPI is not set
CONFIG_SND_USB_AUDIO=y
CONFIG_SND_SOC=y
CONFIG_SND_SOC_ROCKCHIP=y
CONFIG_SND_SOC_ROCKCHIP_SPDIF=y
CONFIG_SND_SOC_ROCKCHIP_HDMI_DP=y
CONFIG_SND_SOC_ROCKCHIP_MAX98090=y
CONFIG_SND_SOC_ROCKCHIP_MULTICODECS=y
CONFIG_SND_SOC_ROCKCHIP_RT5645=y
CONFIG_SND_SOC_ROCKCHIP_CDNDP=y
CONFIG_SND_SOC_ES8316=y
CONFIG_SND_SOC_ES8323=y
CONFIG_SND_SOC_RK3328=y
CONFIG_SND_SOC_RK817=y
CONFIG_SND_SOC_RT5616=y
CONFIG_SND_SOC_RT5640=y
CONFIG_SND_SOC_RT5651=y
CONFIG_SND_SOC_SPDIF=y
CONFIG_SND_SIMPLE_CARD=y
CONFIG_HID_BATTERY_STRENGTH=y
CONFIG_HIDRAW=y
CONFIG_UHID=y
CONFIG_HID_KENSINGTON=y
CONFIG_HID_MULTITOUCH=y
CONFIG_USB_HIDDEV=y
CONFIG_I2C_HID=y
CONFIG_USB_ANNOUNCE_NEW_DEVICES=y
# CONFIG_USB_DEFAULT_PERSIST is not set
CONFIG_USB_OTG=y
CONFIG_USB_MON=y
CONFIG_USB_XHCI_HCD=y
CONFIG_USB_EHCI_HCD=y
CONFIG_USB_EHCI_ROOT_HUB_TT=y
CONFIG_USB_EHCI_HCD_PLATFORM=y
CONFIG_USB_OHCI_HCD=y
# CONFIG_USB_OHCI_HCD_PCI is not set
CONFIG_USB_OHCI_HCD_PLATFORM=y
CONFIG_USB_ACM=y
CONFIG_USB_STORAGE=y
CONFIG_USB_UAS=y
CONFIG_USB_DWC3=y
# CONFIG_USB_DWC3_PCI is not set
CONFIG_USB_DWC2=y
CONFIG_USB_SERIAL=y
CONFIG_USB_SERIAL_GENERIC=y
CONFIG_USB_SERIAL_CH341=y
CONFIG_USB_SERIAL_CP210X=y
CONFIG_USB_SERIAL_FTDI_SIO=y
CONFIG_USB_SERIAL_KEYSPAN=y
CONFIG_USB_SERIAL_PL2303=y
CONFIG_USB_SERIAL_OTI6858=y
CONFIG_USB_SERIAL_QUALCOMM=y
CONFIG_USB_SERIAL_SIERRAWIRELESS=y
CONFIG_USB_SERIAL_OPTION=y
CONFIG_USB_GADGET=y
CONFIG_USB_GADGET_DEBUG_FILES=y
CONFIG_USB_GADGET_VBUS_DRAW=500
CONFIG_USB_CONFIGFS=y
CONFIG_USB_CONFIGFS_ACM=y
CONFIG_USB_CONFIGFS_RNDIS=y
CONFIG_USB_CONFIGFS_MASS_STORAGE=y
CONFIG_USB_CONFIGFS_F_FS=y
CONFIG_USB_CONFIGFS_F_MTP=y
CONFIG_USB_CONFIGFS_UEVENT=y
CONFIG_USB_CONFIGFS_F_UAC1=y
CONFIG_USB_CONFIGFS_F_UAC2=y
CONFIG_USB_CONFIGFS_F_HID=y
CONFIG_USB_CONFIGFS_F_UVC=y
CONFIG_MMC=y
CONFIG_MMC_BLOCK_MINORS=32
CONFIG_MMC_TEST=y
CONFIG_MMC_SDHCI=y
CONFIG_MMC_SDHCI_PLTFM=y
CONFIG_MMC_SDHCI_OF_ARASAN=y
CONFIG_MMC_DW=y
CONFIG_MMC_DW_ROCKCHIP=y
CONFIG_NEW_LEDS=y
CONFIG_LEDS_CLASS=y
CONFIG_LEDS_GPIO=y
CONFIG_LEDS_IS31FL32XX=y
CONFIG_SWITCH=y
CONFIG_RTC_CLASS=y
CONFIG_RTC_DRV_HYM8563=y
CONFIG_RTC_DRV_RK808=y
CONFIG_DMADEVICES=y
CONFIG_PL330_DMA=y
CONFIG_STAGING=y
CONFIG_INV_MPU_IIO=y
CONFIG_SENSORS_ISL29018=y
CONFIG_TSL2583=y
# CONFIG_ANDROID_TIMED_OUTPUT is not set
CONFIG_FIQ_DEBUGGER=y
CONFIG_FIQ_DEBUGGER_NO_SLEEP=y
CONFIG_FIQ_DEBUGGER_CONSOLE=y
CONFIG_FIQ_DEBUGGER_CONSOLE_DEFAULT_ENABLE=y
CONFIG_COMMON_CLK_RK808=y
CONFIG_MAILBOX=y
CONFIG_ROCKCHIP_IOMMU=y
CONFIG_RK_IOMMU=y
CONFIG_RK_IOVMM=y
CONFIG_ROCKCHIP_PM_DOMAINS=y
CONFIG_ROCKCHIP_PVTM=y
CONFIG_ROCKCHIP_SUSPEND_MODE=y
CONFIG_PM_DEVFREQ=y
CONFIG_DEVFREQ_GOV_PERFORMANCE=y
CONFIG_DEVFREQ_GOV_POWERSAVE=y
CONFIG_DEVFREQ_GOV_USERSPACE=y
CONFIG_ARM_ROCKCHIP_DMC_DEVFREQ=y
CONFIG_PM_DEVFREQ_EVENT=y
CONFIG_MEMORY=y
CONFIG_IIO=y
CONFIG_IIO_BUFFER=y
CONFIG_IIO_KFIFO_BUF=y
CONFIG_IIO_TRIGGER=y
CONFIG_ROCKCHIP_SARADC=y
CONFIG_SENSORS_TSL2563=y
CONFIG_IIO_SYSFS_TRIGGER=y
CONFIG_PWM=y
CONFIG_PWM_ROCKCHIP=y
CONFIG_PHY_ROCKCHIP_USB=y
CONFIG_PHY_ROCKCHIP_INNO_USB2=y
CONFIG_PHY_ROCKCHIP_INNO_USB3=y
CONFIG_PHY_ROCKCHIP_EMMC=y
CONFIG_PHY_ROCKCHIP_DP=y
CONFIG_PHY_ROCKCHIP_INNO_MIPI_DPHY=y
CONFIG_PHY_ROCKCHIP_INNO_HDMI_PHY=y
CONFIG_PHY_ROCKCHIP_INNO_VIDEO_COMBO_PHY=y
CONFIG_PHY_ROCKCHIP_TYPEC=y
CONFIG_PHY_ROCKCHIP_PCIE=y
CONFIG_ANDROID=y
CONFIG_NVMEM=y
CONFIG_ROCKCHIP_EFUSE=y
CONFIG_RK_HEADSET=y
CONFIG_ROCKCHIP_SIP=y
# CONFIG_ACPI is not set
CONFIG_EXT4_FS=y
CONFIG_EXT4_FS_POSIX_ACL=y
CONFIG_EXT4_FS_SECURITY=y
CONFIG_XFS_FS=y
CONFIG_BTRFS_FS=y
CONFIG_BTRFS_FS_POSIX_ACL=y
# CONFIG_DNOTIFY is not set
CONFIG_AUTOFS4_FS=y
CONFIG_FUSE_FS=y
CONFIG_OVERLAY_FS=y
CONFIG_ISO9660_FS=y
CONFIG_JOLIET=y
CONFIG_ZISOFS=y
CONFIG_VFAT_FS=y
CONFIG_FAT_DEFAULT_CODEPAGE=936
CONFIG_FAT_DEFAULT_IOCHARSET="utf8"
CONFIG_NTFS_FS=y
CONFIG_TMPFS=y
CONFIG_TMPFS_POSIX_ACL=y
CONFIG_HUGETLBFS=y
CONFIG_CONFIGFS_FS=y
CONFIG_SQUASHFS=y
CONFIG_SQUASHFS_LZ4=y
CONFIG_SQUASHFS_LZO=y
CONFIG_SQUASHFS_XZ=y
CONFIG_PSTORE=y
CONFIG_PSTORE_CONSOLE=y
CONFIG_PSTORE_RAM=y
CONFIG_NFS_FS=y
CONFIG_NFS_V3_ACL=y
CONFIG_NFS_V4=y
CONFIG_NFS_SWAP=y
CONFIG_NFSD=y
CONFIG_NFSD_V4=y
CONFIG_NLS_DEFAULT="utf8"
CONFIG_NLS_CODEPAGE_437=y
CONFIG_NLS_CODEPAGE_936=y
CONFIG_NLS_ASCII=y
CONFIG_NLS_ISO8859_1=y
CONFIG_NLS_UTF8=y
CONFIG_VIRTUALIZATION=y
CONFIG_KVM=y
CONFIG_VHOST_NET=y
CONFIG_VHOST_CROSS_ENDIAN_LEGACY=y
CONFIG_PRINTK_TIME=y
CONFIG_DYNAMIC_DEBUG=y
CONFIG_DEBUG_INFO=y
CONFIG_MAGIC_SYSRQ=y
CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE=0
CONFIG_LOCKUP_DETECTOR=y
CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
CONFIG_BOOTPARAM_HUNG_TASK_PANIC=y
CONFIG_SCHEDSTATS=y
CONFIG_TIMER_STATS=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_CREDENTIALS=y
CONFIG_RCU_CPU_STALL_TIMEOUT=60
CONFIG_FUNCTION_TRACER=y
CONFIG_BLK_DEV_IO_TRACE=y
CONFIG_LKDTM=y
CONFIG_STRICT_DEVMEM=y
CONFIG_DEBUG_SET_MODULE_RONX=y
CONFIG_SECURITY=y
CONFIG_CRYPTO_AUTHENC=y
CONFIG_CRYPTO_ECHAINIV=y
CONFIG_CRYPTO_CBC=y
CONFIG_CRYPTO_SHA1=y
CONFIG_CRYPTO_SHA512=y
CONFIG_CRYPTO_DES=y
CONFIG_CRYPTO_TWOFISH=y
CONFIG_CRYPTO_ANSI_CPRNG=y
CONFIG_CRYPTO_USER_API_HASH=y
CONFIG_CRYPTO_USER_API_SKCIPHER=y
CONFIG_ASYMMETRIC_KEY_TYPE=y
CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
CONFIG_X509_CERTIFICATE_PARSER=y
CONFIG_PKCS7_MESSAGE_PARSER=y
CONFIG_SYSTEM_TRUSTED_KEYRING=y
CONFIG_ARM64_CRYPTO=y
CONFIG_CRYPTO_SHA1_ARM64_CE=y
CONFIG_CRYPTO_SHA2_ARM64_CE=y
CONFIG_CRYPTO_GHASH_ARM64_CE=y
CONFIG_CRYPTO_AES_ARM64_CE_CCM=y
CONFIG_CRYPTO_AES_ARM64_CE_BLK=y
CONFIG_CRC_T10DIF=y
CONFIG_CRC7=y
# CONFIG_XZ_DEC_X86 is not set
# CONFIG_XZ_DEC_POWERPC is not set
# CONFIG_XZ_DEC_IA64 is not set
# CONFIG_XZ_DEC_SPARC is not set

修改成我的配置

CONFIG_WATCHDOG=y
CONFIG_DW_WATCHDOG=y #build-in
CONFIG_SOFT_WATCHDOG=n #不需要
CONFIG_WATCHDOG_CORE=y

或者

CONFIG_WATCHDOG=y
CONFIG_DW_WATCHDOG=m #module
CONFIG_SOFT_WATCHDOG=n #不需要
CONFIG_WATCHDOG_CORE=y

CONFIG_SOFT_WATCHDOG选n就行了，就是不编译，因为有了硬件watchdog，软件watchdog其实就没有那么必要了，可以理解为软件watchdog是硬件watchdog的一个补充。

设备树
kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aioc.dtsi
在这个设备里找到&wdt并将status设置为okay，默认是disable的

&wdt {
        status = "okay";
};

切记保存下

2.开始编译

回到源代码主目录然后进入kernel的目录执行make clean清除以前的编译缓存。然后回到主目录执行

./build.sh aio-3399c-ubuntu.mk

我的是非AI版的，如果你是AI版就执行:

./build.sh aio-3399c-ai-ubuntu.mk

上面的shell是指定编译哪一个board，因为firefly的源代码支持的board种类众多，需要人工指定下。
接下来执行内核编译任务：

./build.sh kernel

如果指定kernel就是只编译内核，我就是只编译内核的，如果你想完整编译就执行：

./build.sh

整个过程不需要sudo权限

3.安装内核

我们不用完整刷机，可以单刷内核，方法也很简单，我们只需要将kernel目录的boot.img复制到设备上然后通过dd拷贝到指定分区就行了，这个地方操作很危险，如果你准备采用我这种方式的话请仔仔细细往下看，否则可能资料全失，欲哭无泪！！！操作前切记备份资料!!

1. 查看分区表
   回到源代码主目录找到rockdev的目录里的paramter.txt，这个文件是一个软链，不过我们并不关心它是啥，我们只看它的内容。每个设备，每个人环境都可能不一样，这个文件的内容也可能不一样，但是大体结构是一样的。

FIRMWARE_VER: 8.1
MACHINE_MODEL: RK3399
MACHINE_ID: 007
MANUFACTURER: RK3399
MAGIC: 0x5041524B
ATAG: 0x00200800
MACHINE: 3399
CHECK_MASK: 0x80
PWR_HLD: 0,0,A,0,1
TYPE: GPT
CMDLINE: mtdparts=rk29xxnand:0x00002000@0x00004000(uboot),0x00002000@0x00006000(trust),0x00002000@0x00008000(misc),0x00020000@0x0000a000(boot),0x00020000@0x0002a000(recovery),0x00010000@0x0004a000(backup),0x00600000@0x0005a000(rootfs),-@0x0065a000(userdata:grow)
uuid:rootfs=614e0000-0000-4b53-8000-1d28000054a9

找到0x00020000@0x0000a000(boot)这个配置，前面的0x00020000是emmc分区的开始位置，这个位置一定不能和前面的分区重合，否则会覆盖并破坏数据，导致系统无法启动，保持默认就好。后面的0x0000a000是从起始位置扩展的空间大小。注意：这个值是sectors，不是B或KB这种单位，sector怎么看可以到设备上看，执行sudo fdisk -l可以看到分区详细信息：

Disk /dev/mmcblk0: 14.6 GiB, 15634268160 bytes, 30535680 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: FB330000-0000-4A61-8000-06380000252A

Device           Start      End  Sectors  Size Type
/dev/mmcblk0p1   16384    24575     8192    4M unknown
/dev/mmcblk0p2   24576    32767     8192    4M unknown
/dev/mmcblk0p3   32768    40959     8192    4M unknown
/dev/mmcblk0p4   40960   172031   131072   64M unknown
/dev/mmcblk0p5  172032   303103   131072   64M unknown
/dev/mmcblk0p6  303104   368639    65536   32M unknown
/dev/mmcblk0p7  368640  4325375  3956736  1.9G unknown
/dev/mmcblk0p8 4325376 30535646 26210271 12.5G unknown

注意这句Units: sectors of 1 * 512 = 512 bytes，说明文件系统的每一个sector占512B，所以上面的boot实际分区大小是10*16^3*512 字节也就是20MB，但事实是我们打出来的boot.img大小是33MB左右，所以这个分区是不是有问题？这里先卖个关子，留在后面解释。

2. 确认分区位置
   从paramter.txt可以看出来我们有8个分区，而boot是第4个分区，也就是上面的

/dev/mmcblk0p4   40960   172031   131072   64M unknown

好，分区已经确认，接下来复写内核。

3. 更新内核

将boot.img复制到需要更新的设备的home目录下，确保设备上至少有大于boot.img的内存空间。执行以下命令：

sudo dd if=boot.img of=/dev/mmcblk0p4

等待写入完成，如果没报错就说明成功了，如果报错了就说明完蛋了，只要你重新启动设备就陷入无限循环了。这个时候只能完整刷机了，运气好的刷入旧的内核可以解决，前提是你的内核不能大于64M，一旦超过这个数可能覆盖后一个分区，导致不可逆的损坏，只能完整镜像抢救了！！！

不出以外你的设备重启进入系统，执行ls /dev会出现watchdog这个字符设备，测试代码如下:

watchdog.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <sys/time.h>
#include <unistd.h>
#include <time.h>
#include <getopt.h>
#include <sys/signal.h>
#include <termios.h>

struct watchdog_info{
    unsigned int options;   //options the card/driver supprots 19
    unsigned int firmware_version;  //firmcard version of the card
    unsigned char identity[32];     //identity of the board 21
 };

#define WATCHDOG_IOCTL_BASE 'W'
#define WDIOC_GETSUPPORT _IOR(WATCHDOG_IOCTL_BASE, 0, struct watchdog_info)
#define WDIOC_SETTIMEOUT _IOWR(WATCHDOG_IOCTL_BASE, 6, int)
#define WDIOC_GETTIMEOUT _IOR(WATCHDOG_IOCTL_BASE, 7, int) //27
#define WDIOS_DISABLECARD 0x0001
#define WDIOS_ENABLECARD 0x0002
#define WDIOC_SETOPTIONS _IOR(WATCHDOG_IOCTL_BASE, 4, int)
#define WDIOC_KEEPALIVE _IOR(WATCHDOG_IOCTL_BASE, 5, int)

int Getch (void)   //无回显的从屏幕输入字符，来达到喂狗的目的

{

     int ch;
     struct termios oldt, newt;   //终端设备结构体
     tcgetattr(STDIN_FILENO, &oldt);   //获得终端属性
     newt = oldt;
     newt.c_lflag &= ~(ECHO|ICANON);   //设置无回显属性
     tcsetattr(STDIN_FILENO, TCSANOW, &newt);  //设置新的终端属性
     ch = getchar();   //从键盘输入一个数据
     tcsetattr(STDIN_FILENO, TCSANOW, &oldt);  //恢复终端设备初始设置
     return ch;

}
 //suspend some seconds
int zsleep(int millisecond)

{
     unsigned long usec;
     usec=1000*millisecond;
     usleep(usec); //usleep(1)睡眠一微秒（10E-6),这里也就是0.1s
}
int Init()
{
     int fd;
     //open device file
     fd = open("/dev/watchdog",O_RDWR);   //打开看门狗设备
      if(fd < 0)
     {
         printf("device open fail\n");
         return -1;
     }
     printf("open success\n");
     return fd;
}

int main(int argc,char **argv)
{
     int fd,ch;
     int i,j;
     char c;
     struct watchdog_info wi;
         if(argc != 2){
                 printf("Usage : ./watchdog 10\n");
                 return -1;
         }
     fd=Init();  //打开终端看门狗设备
         ioctl(fd, WDIOC_SETOPTIONS, WDIOS_ENABLECARD);
     //读板卡信息，但不常用
     ioctl(fd,WDIOC_GETSUPPORT,&wi);
     printf("options is %d,identity is %s\n",wi.options,wi.identity);
     //读看门狗溢出时间

     printf("put_usr return,if 0,success:%d\n",ioctl(fd,WDIOC_GETTIMEOUT,&i));

         printf("The old reset time is: %d\n", i);
     //关闭
      i=WDIOS_DISABLECARD;//WDIOC_SETOPTIONS=0X0001
     printf("return ENOTTY,if -1,success:%d\n",ioctl(fd,WDIOC_SETOPTIONS,&i));
     //打开
      i=WDIOS_ENABLECARD;//WDIOS_ENABLECARD 0x0002
     printf("return ENOTTY,if -1,success:%d\n",ioctl(fd,WDIOC_SETOPTIONS,&i));
     i=atoi(argv[1]);
     printf("put_user return,if 0,success:%d\n",ioctl(fd,WDIOC_SETTIMEOUT,&i));
     //读新的设置时间

     printf("put_usr return,if 0,success:%d\n",ioctl(fd,WDIOC_GETTIMEOUT,&i));


     while(1)
     {
           zsleep(100);
           if((c=Getch())!=27){
                //输入如果不是ESC，就喂狗，否则不喂狗，到时间后系统重启
        printf("keep alive \n");
                ioctl(fd,WDIOC_KEEPALIVE,NULL);
                //write(fd,NULL,1);     //同样是喂狗

           }
     }
    close(fd);   //关闭设备
     return 0;
}

执行:

gcc watchdog.c -o watchdog
sudo ./watchdog 10

成功的话出现下面的提示：

open success
options is 33152,identity is Synopsys DesignWare Watchdog
put_usr return,if 0,success:0
The old reset time is: 21
return ENOTTY,if -1,success:-1
return ENOTTY,if -1,success:-1
put_user return,if 0,success:0
put_usr return,if 0,success:0

一定要open success，Synopsys DesignWare Watchdog出现这个就是基于IP的watchdog，只要不是soft watchdog字样就行了。The old reset time is: 21 这个21就是默认的喂狗间隔，如果超过时间没有敲键盘（喂狗），设备就会自动重新启动，无视一切命令。

4. 线刷内核

本来有了上面的命令已经够用了，还有一种方法是rockchip官方提供的分区刷入，需要借助瑞芯微开发工具。你把boot.img和paramter.txt复制到windows桌面，打开瑞芯微刷机工具，按照我的选，指定两个文件的位置，其他的选项不要勾选，使设备进入boot loader模式然后点击执行，等待刷入完成。

刷入完成之后，系统会重启进入，这个时候就可以测试/dev/watchdog了。

5. linux线刷

其实rockchip还提供了一种基于linux的线刷tool叫upgrade_tool，这里我不说它了，因为我也很少用，而且比windows难用不少，我不推荐。供大家自行研究学习。

6. 多说一句

这里很关键的一个点就是你刷入的boot.img在linux上的大小一定不能超过分区最大容量，比如我前面贴出来的我的boot分区容量是64M，我编译出来的boot.img如果超过64M就不能使用分区刷入了，只能改为完整镜像刷入。还有我前面遗留的问题boot.img有33M而分区表里的容量只有20M，这怎么可能呢？实际上完整镜像是可以刷入的，33M的内核分区也变成了64M，说明检测到容量不够自动扩容了，这个应该是刷机工具完成的，扩容粒度应该是32M的倍数。这个留一个悬念，我还没有完全找到控制扩容的地方。

4.软硬结合

之前说要把软件看门狗和硬件看门狗结合起来，完成一个晚上的看门狗功能，也省去了写代码的烦恼。

sudo apt install watchdog

watchdog知道的是支持Ubuntu、Centos、Debian的，其他的应该也支持，只是我没有用过。

我们要改两个文件

/etc/default/watchdog

# Start watchdog at boot time? 0 or 1
run_watchdog=1
# Start wd_keepalive after stopping watchdog? 0 or 1
run_wd_keepalive=1
# Load module before starting watchdog
#build-in
watchdog_module="none"
#module
#watchdog_module="wd_wdt"
#watchdog_module="Synopsys"
# Specify additional watchdog options here (see manpage).
watchdog_options="-v -s -c /etc/watchdog.conf"

这个地方做个说明：watchdog_module的选项跟着内核构建方式来的，如果刚才选的构建方式是build-in，这个地方用none就行了，填其他的服务启动不起来。如果刚才内核编译选择的是module，就需要手动加载下了。

/etc/watchdog.conf

ping                    = 10.0.20.1
#ping                   = 44.104.88.254
interface               = eth0
#file                   = /var/log/messages
#change                 = 1407

# Uncomment to enable test. Setting one of these values to '0' disables it.
# These values will hopefully never reboot your machine during normal use
# (if your machine is really hung, the loadavg will go much higher than 25)
#max-load-1             = 24
#max-load-5             = 18
#max-load-15            = 12

# Note that this is the number of pages!
# To get the real size, check how large the pagesize is on your machine.
#min-memory             = 1
#allocatable-memory     = 1

#repair-binary          = /usr/sbin/repair
#repair-timeout         = 60
#test-binary            =
#test-timeout           = 60

# The retry-timeout and repair limit are used to handle errors in a more robust
# manner. Errors must persist for longer than retry-timeout to action a repair
# or reboot, and if repair-maximum attempts are made without the test passing a
# reboot is initiated anyway.
#retry-timeout          = 30
#repair-maximum         = 1

watchdog-device = /dev/watchdog

# Defaults compiled into the binary
temperature-sensor      = /sys/class/thermal/thermal_zone0/temp
max-temperature         = 90

# Defaults compiled into the binary
admin                   = root
interval                = 10
logtick                 = 60
log-dir                 = /var/log/watchdog

# This greatly decreases the chance that watchdog won't be scheduled before
# your machine is really loaded
realtime                = yes
priority                = 1

# Check if rsyslogd is still running by enabling the following line
pidfile                 = /var/run/rsyslogd.pid
pidfile                 = /var/run/sshd.pid
pidfile                 = /var/run/inetd.pid

watchdog-timeout        = 60

接着执行:

sudo systemctl start watchdog
systemctl status watchdog

如果没报错就是成功了，可喜可贺，终于还是到了这一步。至于watchdog.conf里的配置含义，我的另一篇博客说的很明白了，大家可以参照下看看。每一项的测试方法我就不说了，我每一个都测过了，效果很好，有不懂的可以评论区问我。

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总结

1、不同的设备肯定不太一样，如果你和我设备一样或相近，那肯定适用于你。
2、整个流程完整测试下来，证明是可行的。
3、有问题请留言，我看到了会回复你的。