1*4882a593Smuzhiyun============================================================ 2*4882a593SmuzhiyunWDT Watchdog Timer Interfaces For The Linux Operating System 3*4882a593Smuzhiyun============================================================ 4*4882a593Smuzhiyun 5*4882a593SmuzhiyunLast Reviewed: 10/05/2007 6*4882a593Smuzhiyun 7*4882a593SmuzhiyunAlan Cox <alan@lxorguk.ukuu.org.uk> 8*4882a593Smuzhiyun 9*4882a593Smuzhiyun - ICS WDT501-P 10*4882a593Smuzhiyun - ICS WDT501-P (no fan tachometer) 11*4882a593Smuzhiyun - ICS WDT500-P 12*4882a593Smuzhiyun 13*4882a593SmuzhiyunAll the interfaces provide /dev/watchdog, which when open must be written 14*4882a593Smuzhiyunto within a timeout or the machine will reboot. Each write delays the reboot 15*4882a593Smuzhiyuntime another timeout. In the case of the software watchdog the ability to 16*4882a593Smuzhiyunreboot will depend on the state of the machines and interrupts. The hardware 17*4882a593Smuzhiyunboards physically pull the machine down off their own onboard timers and 18*4882a593Smuzhiyunwill reboot from almost anything. 19*4882a593Smuzhiyun 20*4882a593SmuzhiyunA second temperature monitoring interface is available on the WDT501P cards. 21*4882a593SmuzhiyunThis provides /dev/temperature. This is the machine internal temperature in 22*4882a593Smuzhiyundegrees Fahrenheit. Each read returns a single byte giving the temperature. 23*4882a593Smuzhiyun 24*4882a593SmuzhiyunThe third interface logs kernel messages on additional alert events. 25*4882a593Smuzhiyun 26*4882a593SmuzhiyunThe ICS ISA-bus wdt card cannot be safely probed for. Instead you need to 27*4882a593Smuzhiyunpass IO address and IRQ boot parameters. E.g.:: 28*4882a593Smuzhiyun 29*4882a593Smuzhiyun wdt.io=0x240 wdt.irq=11 30*4882a593Smuzhiyun 31*4882a593SmuzhiyunOther "wdt" driver parameters are: 32*4882a593Smuzhiyun 33*4882a593Smuzhiyun =========== ====================================================== 34*4882a593Smuzhiyun heartbeat Watchdog heartbeat in seconds (default 60) 35*4882a593Smuzhiyun nowayout Watchdog cannot be stopped once started (kernel 36*4882a593Smuzhiyun build parameter) 37*4882a593Smuzhiyun tachometer WDT501-P Fan Tachometer support (0=disable, default=0) 38*4882a593Smuzhiyun type WDT501-P Card type (500 or 501, default=500) 39*4882a593Smuzhiyun =========== ====================================================== 40*4882a593Smuzhiyun 41*4882a593SmuzhiyunFeatures 42*4882a593Smuzhiyun-------- 43*4882a593Smuzhiyun 44*4882a593Smuzhiyun================ ======= ======= 45*4882a593Smuzhiyun WDT501P WDT500P 46*4882a593Smuzhiyun================ ======= ======= 47*4882a593SmuzhiyunReboot Timer X X 48*4882a593SmuzhiyunExternal Reboot X X 49*4882a593SmuzhiyunI/O Port Monitor o o 50*4882a593SmuzhiyunTemperature X o 51*4882a593SmuzhiyunFan Speed X o 52*4882a593SmuzhiyunPower Under X o 53*4882a593SmuzhiyunPower Over X o 54*4882a593SmuzhiyunOverheat X o 55*4882a593Smuzhiyun================ ======= ======= 56*4882a593Smuzhiyun 57*4882a593SmuzhiyunThe external event interfaces on the WDT boards are not currently supported. 58*4882a593SmuzhiyunMinor numbers are however allocated for it. 59*4882a593Smuzhiyun 60*4882a593Smuzhiyun 61*4882a593SmuzhiyunExample Watchdog Driver: 62*4882a593Smuzhiyun 63*4882a593Smuzhiyun see samples/watchdog/watchdog-simple.c 64