From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753250Ab3KYXXg (ORCPT ); Mon, 25 Nov 2013 18:23:36 -0500 Received: from mail.active-venture.com ([67.228.131.205]:56161 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756Ab3KYXXc (ORCPT ); Mon, 25 Nov 2013 18:23:32 -0500 X-Originating-IP: 108.223.40.66 Message-ID: <5293DBEF.3010401@roeck-us.net> Date: Mon, 25 Nov 2013 15:23:27 -0800 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Doug Anderson , Wim Van Sebroeck CC: Leela Krishna Amudala , Olof Johansson , Tomasz Figa , Kukjin Kim , Ben Dooks , 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] watchdog: s3c2410_wdt: Only register for cpufreq on CPU_FREQ_S3C24XX References: <1385420137-32725-1-git-send-email-dianders@chromium.org> In-Reply-To: <1385420137-32725-1-git-send-email-dianders@chromium.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/25/2013 02:55 PM, 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 > CPU_FREQ_S3C24XX 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 CPU_FREQ_S3C24XX 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 > --- > drivers/watchdog/s3c2410_wdt.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c > index 7d8fd04..4980f84 100644 > --- a/drivers/watchdog/s3c2410_wdt.c > +++ b/drivers/watchdog/s3c2410_wdt.c > @@ -264,7 +264,7 @@ static irqreturn_t s3c2410wdt_irq(int irqno, void *param) > return IRQ_HANDLED; > } > > -#ifdef CONFIG_CPU_FREQ > +#ifdef CONFIG_CPU_FREQ_S3C24XX > Where is the CPU_FREQ_S3C24XX configuration option defined ? I don't see it in the current upstream kernel, so it appears that this depends on some out-of-tree changes. Thanks, Guenter