cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

wdt.rst (2200B)

      1============================================================
      2WDT Watchdog Timer Interfaces For The Linux Operating System
      3============================================================
      4
      5Last Reviewed: 10/05/2007
      6
      7Alan Cox <alan@lxorguk.ukuu.org.uk>
      8
      9	- ICS	WDT501-P
     10	- ICS	WDT501-P (no fan tachometer)
     11	- ICS	WDT500-P
     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
     20A second temperature monitoring interface is available on the WDT501P cards.
     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
     26The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to
     27pass IO address and IRQ boot parameters.  E.g.::
     28
     29	wdt.io=0x240 wdt.irq=11
     30
     31Other "wdt" driver parameters are:
     32
     33	===========	======================================================
     34	heartbeat	Watchdog heartbeat in seconds (default 60)
     35	nowayout	Watchdog cannot be stopped once started (kernel
     36			build parameter)
     37	tachometer	WDT501-P Fan Tachometer support (0=disable, default=0)
     38	type		WDT501-P Card type (500 or 501, default=500)
     39	===========	======================================================
     40
     41Features
     42--------
     43
     44================   =======	   =======
     45		   WDT501P	   WDT500P
     46================   =======	   =======
     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
     55================   =======	   =======
     56
     57The external event interfaces on the WDT boards are not currently supported.
     58Minor numbers are however allocated for it.
     59
     60
     61Example Watchdog Driver:
     62
     63	see samples/watchdog/watchdog-simple.c