linux-kernel - Re: [PATCH] Add watchdog driver for w90p910

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Date:	Wed, 5 Aug 2009 12:31:27 +0200
From:	Wim Van Sebroeck <wim@...ana.be>
To:	Wan ZongShun <mcuos.com@...il.com>
Cc:	linux-arm-kernel <linux-arm-kernel@...ts.arm.linux.org.uk>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add watchdog driver for w90p910

Hi Wan,

> > I have an additional question: which timeout values can you set? is it 0, 1, 2 and 3 seconds?
> 
> The 0, 1, 2 and 3 is not seconds, rather than 'level' , it means my
> watchdog controller can only set four grades,
> When WTIS bit of REG_WTCR was set one value of  the 0, 1, 2 and 3, the
>  real time interval can be calculated via following formula .
> 
> WTIS                 real time interval (formula)
> 0x00                   ((2^ 14 ) * ((external crystal freq) / 256))seconds
> 0x01                   ((2^ 16 ) * ((external crystal freq) / 256))seconds
> 0x02                   ((2^ 18 ) * ((external crystal freq) / 256))seconds
> 0x03                   ((2^ 20 ) * ((external crystal freq) / 256))seconds
> 
> The external crystal freq is 15Mhz in w90p910 evaluation board. so I
> set the '0x00' as a default value, it means the real time interval is
> 0.28 second approximately.

Hmm, the watchdog API works in seconds.
A timer will need to be used like in similar watchdog drivers (like at91sam9_wdt.c, pcwd.c).

Kind regards,
Wim.

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