linux-kernel - Re: Questions about Watch Dog Timer under Linux.

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Message-ID: <f9f38a550912110038y51c4d4c4g35b6267efca69d71@mail.gmail.com>
Date:	Fri, 11 Dec 2009 16:38:27 +0800
From:	Cypher Wu <cypher.w@...il.com>
To:	Pádraig Brady <P@...igbrady.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Questions about Watch Dog Timer under Linux.

Less than 2 seconds is not a thing in our embedded system, the WDT
we've already used will time out every 1.6s, and only a WDI connection
to support timer clearing. I'm not sure if we depend on a user
application to clearing the dog directly, is this too short for Linux
since it's not a RTOS.

2009/12/10 Pádraig Brady <P@...igbrady.com>:
> On 09/12/09 14:47, Cypher Wu wrote:
>>
>> I'm used to work on embedded systems, the Watch Dog Timer in our
>> products is usually a seperate chip on the board wich will start to
>> work after power reset and will time out in 2 seconds. The system has
>> to start dog clearing from the very beginning and there have no way to
>> disable WDT.
>
> wow 2 seconds :(
>
> It's easy to patch grub stage 1 to pat the watchdog.
> I was even able to get support for the complicated iTCO intel
> watchdogs in there, though your watchdog may be much simpler.
>
> Then when the kernel started it patted the watchdog as normal.
>
> Note I did this to support robust remote upgrade (as the boot
> loader wasn't touched on upgrade), rather than to support a
> very short timeout.
>
> cheers,
> Pádraig.
>
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