Messages in this thread | | | Date | Thu, 14 May 2015 06:30:05 -0700 | From | Guenter Roeck <> | Subject | Re: Window watchdog driver design |
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On 05/14/2015 04:56 AM, Andreas Werner wrote: > Hi, > in the next few weeks I need to write a driver for a window wachtdog > implemented in a CPLD. I have some questions about the design > of the driver and the best way to write this driver to also be able > to submit it. > > The triggering and configuration of the Watchdog is done by several GPIOs which > are connected to the CPLD watchdog device. The correct GPIOs are configurable > using the Device Tree. > > 1. Timeout > The timeout values are defined in ms and start from 20ms to 2560ms. > The timout is set by 3 GPIOs this means we have only 8 different > timout values. It is also possible that a future Watchdog CPLD device > does have different timeout values. > > Is it possible to set ms timeouts? It seems that the WDT API does > only support a resolution of 1sec. > > One idea would be to use the API timeout as something like a timeout > index to set the different values. Of course this needs to be documented. > > e.g. > timeout (API) timeout in device > 1 20ms > 2 100ms > 3 500ms > ... ... > > 2. Upper/Lower Window > There is currently no support for a windowed watchdog in the wdt core. > The lower window can be activated by a gpio and its timeout is defined > as "upper windows timeout/4" > > What is the best way to implement those additional settings? Adding additional > ioctl or export these in sysfs? > --
Sorry for the maybe dumb question, but what is a window watchdog, and what is the lower window timeout for (assuming the upper window timeout causes the watchdog to expire) ?
Guenter
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