From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753580Ab3KYX2E (ORCPT ); Mon, 25 Nov 2013 18:28:04 -0500 Received: from mail-bk0-f53.google.com ([209.85.214.53]:46334 "EHLO mail-bk0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753362Ab3KYX1o (ORCPT ); Mon, 25 Nov 2013 18:27:44 -0500 From: Tomasz Figa To: Guenter Roeck Cc: Doug Anderson , Wim Van Sebroeck , Leela Krishna Amudala , Olof Johansson , 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 Date: Tue, 26 Nov 2013 00:27:41 +0100 Message-ID: <1832773.UG2ItueiDl@flatron> User-Agent: KMail/4.11.3 (Linux/3.12.0-gentoo; KDE/4.11.3; x86_64; ; ) In-Reply-To: <5293DBEF.3010401@roeck-us.net> References: <1385420137-32725-1-git-send-email-dianders@chromium.org> <5293DBEF.3010401@roeck-us.net> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 25 of November 2013 15:23:27 Guenter Roeck wrote: > 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. Seems like it got renamed to ARM_S3C24XX_CPUFREQ by f023f8dd59. Best regards, Tomasz