linux-kernel - Re: [PATCH] fix book E watchdog to take WDIOC

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Message-ID: <20090827202709.GK29382@infomag.iguana.be>
Date:	Thu, 27 Aug 2009 22:27:09 +0200
From:	Wim Van Sebroeck <wim@...ana.be>
To:	Josh Boyer <jwboyer@...ux.vnet.ibm.com>
Cc:	Chris Friesen <cfriesen@...tel.com>, linuxppc-dev@...abs.org,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fix book E watchdog to take WDIOC_SETTIMEOUT arg in
	seconds

Hi Josh,

> >Now we only need someone that can look at the CONFIG_4xx cases still :-)
> 
> It seems the FSL watchdog is much more flexible than the one found in 4xx
> cores.  On 4xx, you basically have 4 static choices that represent specific
> times determined by the clock frequency.  I'm concerned that the lack of
> granularity here will result in less than desirable behavior.
> 
> For example, with a 400MHz clock you would get choices of roughly:
> 
> 5.2 ms
> 83.9 ms
> 1.34 s
> 21.47 s
> 
> Personally, I consider the first two options basically unusable.  Considering
> the second two, if a user were to say "Set the timeout for 2 seconds" they
> would then get a timeout of 21 seconds with the framework Chris' patch has
> set up.  That doesn't really seem to be ideal to me.

Hmm, my opinion: in that case we should use a timer that triggers the watchdog until userspaces times out (like we do for other watchdogs allready). Maybe we should split this driver. I have the same issue with the Freescale i.mx driver that is under review also.

Kind regards,
Wim.

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