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Documentation/watchdog/: Expose example and tool source files in the Documentation/ directory in their own files instead of being buried (almost hidden) in readme/txt files. This will make them more visible/usable to users who may need to use them, to developers who may need to test with them, and to janitors who would update them if they were more visible. Also, if any of these possibly should not be in the kernel tree at all, it will be clearer that they are here and we can discuss if they should be removed. Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Signed-off-by: Andrew Morton <akpm@osdl.org>
95 lines
3.5 KiB
Plaintext
95 lines
3.5 KiB
Plaintext
Watchdog Timer Interfaces For The Linux Operating System
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Alan Cox <alan@lxorguk.ukuu.org.uk>
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Custom Linux Driver And Program Development
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The following watchdog drivers are currently implemented:
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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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Software Only
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SA1100 Internal Watchdog
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Berkshire Products PC Watchdog Revision A & C (by Ken Hollis)
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All six 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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A second temperature monitoring interface is available on the WDT501P cards
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and some Berkshire cards. This provides /dev/temperature. This is the machine
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internal temperature in degrees Fahrenheit. Each read returns a single byte
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giving the temperature.
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The third interface logs kernel messages on additional alert events.
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Both software and hardware watchdog drivers are available in the standard
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kernel. If you are using the software watchdog, you probably also want
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to use "panic=60" as a boot argument as well.
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The wdt card cannot be safely probed for. Instead you need to pass
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wdt=ioaddr,irq as a boot parameter - eg "wdt=0x240,11".
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The SA1100 watchdog module can be configured with the "sa1100_margin"
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commandline argument which specifies timeout value in seconds.
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The i810 TCO watchdog modules can be configured with the "i810_margin"
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commandline argument which specifies the counter initial value. The counter
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is decremented every 0.6 seconds and default to 50 (30 seconds). Values can
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range between 3 and 63.
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The i810 TCO watchdog driver also implements the WDIOC_GETSTATUS and
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WDIOC_GETBOOTSTATUS ioctl()s. WDIOC_GETSTATUS returns the actual counter value
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and WDIOC_GETBOOTSTATUS returns the value of TCO2 Status Register (see Intel's
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documentation for the 82801AA and 82801AB datasheet).
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Features
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--------
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WDT501P WDT500P Software Berkshire i810 TCO SA1100WD
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Reboot Timer X X X X X X
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External Reboot X X o o o X
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I/O Port Monitor o o o X o o
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Temperature X o o X o o
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Fan Speed X o o o o o
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Power Under X o o o o o
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Power Over X o o o o o
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Overheat X o o o o 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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Contact Information
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People keep asking about the WDT watchdog timer hardware: The phone contacts
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for Industrial Computer Source are:
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Industrial Computer Source
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http://www.indcompsrc.com
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ICS Advent, San Diego
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6260 Sequence Dr.
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San Diego, CA 92121-4371
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Phone (858) 677-0877
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FAX: (858) 677-0895
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>
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ICS Advent Europe, UK
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Oving Road
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Chichester,
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West Sussex,
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PO19 4ET, UK
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Phone: 00.44.1243.533900
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and please mention Linux when enquiring.
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For full information about the PCWD cards see the pcwd-watchdog.txt document.
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