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review.shift-gmbh.com / SHIFTPHONES / mainline / linux / 7fbf6795d127a3b1bb39b0e42579904cf6db1624 / . / Documentation / watchdog / wdt.rst
blob: d97b0361535b0986f79732cdacaabf0ba581b681 [file] [log] [blame]
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]1============================================================
2WDT Watchdog Timer Interfaces For The Linux Operating System
3============================================================
4
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]5Last Reviewed: 10/05/2007
6
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]7Alan Cox <alan@lxorguk.ukuu.org.uk>
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]8
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]9 - ICS WDT501-P
10 - ICS WDT501-P (no fan tachometer)
11 - ICS WDT500-P
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]12
13All the interfaces provide /dev/watchdog, which when open must be written
14to within a timeout or the machine will reboot. Each write delays the reboot
15time another timeout. In the case of the software watchdog the ability to
16reboot will depend on the state of the machines and interrupts. The hardware
17boards physically pull the machine down off their own onboard timers and
18will reboot from almost anything.
19
Randy Dunlap4724ba572010-05-03 11:42:52 -0700[diff] [blame]20A second temperature monitoring interface is available on the WDT501P cards.
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]21This provides /dev/temperature. This is the machine internal temperature in
22degrees Fahrenheit. Each read returns a single byte giving the temperature.
23
24The third interface logs kernel messages on additional alert events.
25
Randy Dunlap4724ba572010-05-03 11:42:52 -0700[diff] [blame]26The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]27pass IO address and IRQ boot parameters. E.g.::
28
Randy Dunlap4724ba572010-05-03 11:42:52 -0700[diff] [blame]29 wdt.io=0x240 wdt.irq=11
30
31Other "wdt" driver parameters are:
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]32
33 =========== ======================================================
Randy Dunlap4724ba572010-05-03 11:42:52 -0700[diff] [blame]34 heartbeat Watchdog heartbeat in seconds (default 60)
35 nowayout Watchdog cannot be stopped once started (kernel
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]36 build parameter)
Randy Dunlap4724ba572010-05-03 11:42:52 -0700[diff] [blame]37 tachometer WDT501-P Fan Tachometer support (0=disable, default=0)
38 type WDT501-P Card type (500 or 501, default=500)
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]39 =========== ======================================================
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]40
41Features
42--------
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]43
44================ ======= =======
45 WDT501P WDT500P
46================ ======= =======
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]47Reboot Timer X X
48External Reboot X X
49I/O Port Monitor o o
50Temperature X o
51Fan Speed X o
52Power Under X o
53Power Over X o
54Overheat X o
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]55================ ======= =======
Alan Cox4d389dc2007-05-23 14:43:52 -0700[diff] [blame]56
57The external event interfaces on the WDT boards are not currently supported.
58Minor numbers are however allocated for it.
59
60
Mauro Carvalho Chehabcc2a2d12019-06-12 14:53:01 -0300[diff] [blame]61Example Watchdog Driver:
62
63 see samples/watchdog/watchdog-simple.c