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From: Guenter Roeck <linux@roeck-us.net>
To: Doug Anderson <dianders@chromium.org>, Wim Van Sebroeck <wim@iguana.be>
Cc: Heiko Stuebner <heiko@sntech.de>,
	Lunxue Dai <lunxue.dai@rock-chips.com>,
	Jisheng Zhang <jszhang@marvell.com>,
	Dinh Nguyen <dinguyen@altera.com>,
	linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] watchdog: dw_wdt: pat the watchdog before enabling it
Date: Wed, 21 Jan 2015 15:35:40 -0800	[thread overview]
Message-ID: <54C037CC.2070707@roeck-us.net> (raw)
In-Reply-To: <1421882243-3631-1-git-send-email-dianders@chromium.org>

On 01/21/2015 03:17 PM, Doug Anderson wrote:
> On some dw_wdt implementations the "top" register may be initted to 0
> at bootup.  In such a case, each "pat" of the watchdog will reset the
> timer to 0xffff.  That's pretty short.
>
> The input clock of the wdt can be any of a wide range of values.  On
> an rk3288 system, I've seen the wdt clock be 24.75 MHz.  That means
> each tick is ~40ns and we'll count to 0xffff in ~2.6ms.
>
> Because of the above two facts, it's a really good idea to pat the
> watchdog after initting the "top" register properly and before
> enabling the watchdog.  If you don't then there's no way we'll get the
> next heartbeat in time.
>
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> ---

Reviewed-by: Guenter Roeck <linux@roeck-us.net>


  parent reply	other threads:[~2015-01-21 23:35 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-21 23:17 Doug Anderson
2015-01-21 23:17 ` [PATCH 2/2] watchdog: dw_wdt: Try to get a 30 second watchdog by default Doug Anderson
2015-01-21 23:36   ` Guenter Roeck
2015-01-21 23:35 ` Guenter Roeck [this message]
2015-01-22  5:22 ` [PATCH 1/2] watchdog: dw_wdt: pat the watchdog before enabling it Jisheng Zhang
2015-01-22  5:31   ` Guenter Roeck
2015-01-22 17:09   ` Doug Anderson
2015-01-23 16:03     ` Guenter Roeck
2015-01-23 16:20       ` Doug Anderson
2015-01-23 17:02         ` Guenter Roeck
2015-01-26  6:22     ` Jisheng Zhang
2015-01-26 17:01       ` Doug Anderson
2015-01-27  3:44         ` Jisheng Zhang
2015-01-27  4:07           ` Guenter Roeck
2015-01-27  4:36             ` Jisheng Zhang

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