From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 8 Jan 2014 20:54:48 +0100 From: Wim Van Sebroeck To: Doug Anderson Cc: Guenter Roeck , 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 v2] watchdog: s3c2410_wdt: Only register for cpufreq on ARM_S3C24XX_CPUFREQ Message-ID: <20140108195448.GA30865@spo001.leaseweb.com> References: <1385420137-32725-1-git-send-email-dianders@chromium.org> <1385422603-22684-1-git-send-email-dianders@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1385422603-22684-1-git-send-email-dianders@chromium.org> Sender: List-ID: Hi Doug, > 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 > --- > Changes in v2: > - Use the updated config name. Patch added to linux-watchdog-next. Kind regards, Wim.