From: Guenter Roeck <linux@roeck-us.net>
To: Doug Anderson <dianders@chromium.org>
Cc: Wim Van Sebroeck <wim@iguana.be>,
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 v3 1/2] watchdog: dw_wdt: pat the watchdog before enabling it
Date: Wed, 28 Jan 2015 10:58:43 -0800 [thread overview]
Message-ID: <20150128185843.GB6730@roeck-us.net> (raw)
In-Reply-To: <1422397517-20426-1-git-send-email-dianders@chromium.org>
On Tue, Jan 27, 2015 at 02:25:16PM -0800, 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.
>
> Jisheng Zhang fixed this problem on some dw_wdt versions by using the
> TOP_INIT feature. However, the dw_wdt on rk3288 doesn't have TOP_INIT
> so it's a good idea to also pat the watchdog manually.
>
> Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
next prev parent reply other threads:[~2015-01-28 20:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-27 22:25 [PATCH v3 1/2] watchdog: dw_wdt: pat the watchdog before enabling it Doug Anderson
2015-01-27 22:25 ` [PATCH v3 2/2] watchdog: dw_wdt: Try to get a 30 second watchdog by default Doug Anderson
2015-02-03 19:02 ` Wim Van Sebroeck
2015-01-28 1:38 ` [PATCH v3 1/2] watchdog: dw_wdt: pat the watchdog before enabling it Jisheng Zhang
2015-01-28 18:58 ` Guenter Roeck [this message]
2015-02-03 19:01 ` Wim Van Sebroeck
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