2007-05-24 05:43:52 +08:00
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Last Reviewed: 10/05/2007
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WDT Watchdog Timer Interfaces For The Linux Operating System
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Alan Cox <alan@lxorguk.ukuu.org.uk>
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ICS WDT501-P
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ICS WDT501-P (no fan tachometer)
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ICS WDT500-P
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All the interfaces provide /dev/watchdog, which when open must be written
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to within a timeout or the machine will reboot. Each write delays the reboot
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time another timeout. In the case of the software watchdog the ability to
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reboot will depend on the state of the machines and interrupts. The hardware
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boards physically pull the machine down off their own onboard timers and
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will reboot from almost anything.
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2010-05-04 02:42:52 +08:00
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A second temperature monitoring interface is available on the WDT501P cards.
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2007-05-24 05:43:52 +08:00
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This provides /dev/temperature. This is the machine internal temperature in
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degrees Fahrenheit. Each read returns a single byte giving the temperature.
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The third interface logs kernel messages on additional alert events.
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2010-05-04 02:42:52 +08:00
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The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to
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pass IO address and IRQ boot parameters. E.g.:
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wdt.io=0x240 wdt.irq=11
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Other "wdt" driver parameters are:
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heartbeat Watchdog heartbeat in seconds (default 60)
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nowayout Watchdog cannot be stopped once started (kernel
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build parameter)
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tachometer WDT501-P Fan Tachometer support (0=disable, default=0)
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type WDT501-P Card type (500 or 501, default=500)
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2007-05-24 05:43:52 +08:00
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Features
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--------
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WDT501P WDT500P
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Reboot Timer X X
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External Reboot X X
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I/O Port Monitor o o
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Temperature X o
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Fan Speed X o
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Power Under X o
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Power Over X o
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Overheat X o
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The external event interfaces on the WDT boards are not currently supported.
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Minor numbers are however allocated for it.
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Example Watchdog Driver: see Documentation/watchdog/src/watchdog-simple.c
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