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diff --git a/Documentation/watchdog/watchdog.txt b/Documentation/watchdog/watchdog.txt new file mode 100644 index 000000000000..dffda29c8799 --- /dev/null +++ b/Documentation/watchdog/watchdog.txt @@ -0,0 +1,115 @@ + Watchdog Timer Interfaces For The Linux Operating System + + Alan Cox <alan@lxorguk.ukuu.org.uk> + + Custom Linux Driver And Program Development + + +The following watchdog drivers are currently implemented: + + ICS WDT501-P + ICS WDT501-P (no fan tachometer) + ICS WDT500-P + Software Only + SA1100 Internal Watchdog + Berkshire Products PC Watchdog Revision A & C (by Ken Hollis) + + +All six interfaces provide /dev/watchdog, which when open must be written +to within a timeout or the machine will reboot. Each write delays the reboot +time another timeout. In the case of the software watchdog the ability to +reboot will depend on the state of the machines and interrupts. The hardware +boards physically pull the machine down off their own onboard timers and +will reboot from almost anything. + +A second temperature monitoring interface is available on the WDT501P cards +and some Berkshire cards. This provides /dev/temperature. This is the machine +internal temperature in degrees Fahrenheit. Each read returns a single byte +giving the temperature. + +The third interface logs kernel messages on additional alert events. + +Both software and hardware watchdog drivers are available in the standard +kernel. If you are using the software watchdog, you probably also want +to use "panic=60" as a boot argument as well. + +The wdt card cannot be safely probed for. Instead you need to pass +wdt=ioaddr,irq as a boot parameter - eg "wdt=0x240,11". + +The SA1100 watchdog module can be configured with the "sa1100_margin" +commandline argument which specifies timeout value in seconds. + +The i810 TCO watchdog modules can be configured with the "i810_margin" +commandline argument which specifies the counter initial value. The counter +is decremented every 0.6 seconds and default to 50 (30 seconds). Values can +range between 3 and 63. + +The i810 TCO watchdog driver also implements the WDIOC_GETSTATUS and +WDIOC_GETBOOTSTATUS ioctl()s. WDIOC_GETSTATUS returns the actual counter value +and WDIOC_GETBOOTSTATUS returns the value of TCO2 Status Register (see Intel's +documentation for the 82801AA and 82801AB datasheet). + +Features +-------- + WDT501P WDT500P Software Berkshire i810 TCO SA1100WD +Reboot Timer X X X X X X +External Reboot X X o o o X +I/O Port Monitor o o o X o o +Temperature X o o X o o +Fan Speed X o o o o o +Power Under X o o o o o +Power Over X o o o o o +Overheat X o o o o o + +The external event interfaces on the WDT boards are not currently supported. +Minor numbers are however allocated for it. + + +Example Watchdog Driver +----------------------- + +#include <stdio.h> +#include <unistd.h> +#include <fcntl.h> + +int main(int argc, const char *argv[]) +{ + int fd=open("/dev/watchdog",O_WRONLY); + if(fd==-1) + { + perror("watchdog"); + exit(1); + } + while(1) + { + write(fd,"\0",1); + fsync(fd); + sleep(10); + } +} + + +Contact Information + +People keep asking about the WDT watchdog timer hardware: The phone contacts +for Industrial Computer Source are: + +Industrial Computer Source +http://www.indcompsrc.com +ICS Advent, San Diego +6260 Sequence Dr. +San Diego, CA 92121-4371 +Phone (858) 677-0877 +FAX: (858) 677-0895 +> +ICS Advent Europe, UK +Oving Road +Chichester, +West Sussex, +PO19 4ET, UK +Phone: 00.44.1243.533900 + + +and please mention Linux when enquiring. + +For full information about the PCWD cards see the pcwd-watchdog.txt document. |