From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753734Ab3KZAD4 (ORCPT <rfc822;w@1wt.eu>);
	Mon, 25 Nov 2013 19:03:56 -0500
Received: from mail-bk0-f42.google.com ([209.85.214.42]:46465 "EHLO
	mail-bk0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753680Ab3KZADv (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 25 Nov 2013 19:03:51 -0500
From: Tomasz Figa <tomasz.figa@gmail.com>
To: Doug Anderson <dianders@chromium.org>
Cc: Wim Van Sebroeck <wim@iguana.be>, Guenter Roeck <linux@roeck-us.net>,
        Leela Krishna Amudala <l.krishna@samsung.com>,
        Olof Johansson <olof@lixom.net>, Kukjin Kim <kgene.kim@samsung.com>,
        Ben Dooks <ben-linux@fluff.org>, linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-watchdog@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] watchdog: s3c2410_wdt: Only register for cpufreq on ARM_S3C24XX_CPUFREQ
Date: Tue, 26 Nov 2013 01:03:49 +0100
Message-ID: <12609399.rlV8OtdFZt@flatron>
User-Agent: KMail/4.11.3 (Linux/3.12.0-gentoo; KDE/4.11.3; x86_64; ; )
In-Reply-To: <1385422603-22684-1-git-send-email-dianders@chromium.org>
References: <1385420137-32725-1-git-send-email-dianders@chromium.org> <1385422603-22684-1-git-send-email-dianders@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Monday 25 of November 2013 15:36:43 Doug Anderson wrote:
> On modern SoCs the watchdog timer is parented on a clock that doesn't
> change every time we have a cpufreq change.  That means we don't need
> to constantly adjust the watchdog timer, so avoid registering for and
> dealing with cpufreq transitions unless we've actually got
> CONFIG_ARM_S3C24XX_CPUFREQ defined.
> 
> Note that this is more than just an optimization.  The s3c2410
> watchdog driver actually pats the watchdog on every CPU frequency
> change.  On modern systems these happen many times per second (even in
> a system where "nothing" is happening).  That effectively makes any
> userspace watchdog program useless (the watchdog is constantly patted
> by the kernel).  If we need ARM_S3C24XX_CPUFREQ defined on a
> multiplatform kernel we'll need to make sure that kernel supports
> common clock and change this to user common clock framework.
> 
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> ---
> Changes in v2:
> - Use the updated config name.
> 
>  drivers/watchdog/s3c2410_wdt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Tomasz Figa <t.figa@samsung.com>

Best regards,
Tomasz