Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753353Ab3EaKJU (ORCPT ); Fri, 31 May 2013 06:09:20 -0400 Received: from mail.active-venture.com ([67.228.131.205]:58135 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751864Ab3EaKJL (ORCPT ); Fri, 31 May 2013 06:09:11 -0400 X-Originating-IP: 108.223.40.66 Date: Fri, 31 May 2013 03:09:41 -0700 From: Guenter Roeck To: anish singh Cc: Wim Van Sebroeck , Johannes Thumshirn , linux-watchdog@vger.kernel.org, linux-kernel-mail Subject: Re: [PATCH v4 1/2] watchdog: New watchdog driver for MEN A21 watchdogs Message-ID: <20130531100941.GA31434@roeck-us.net> References: <20130527090756.GA14258@spo001.leaseweb.com> <1369678434-13515-1-git-send-email-johannes.thumshirn@men.de> <20130527182554.GB14258@spo001.leaseweb.com> <20130528081053.GC818@jtlinux> <20130528162218.GA22351@roeck-us.net> <20130530215928.GL14258@spo001.leaseweb.com> <20130530220247.GA2275@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1943 Lines: 45 On Fri, May 31, 2013 at 03:05:50PM +0530, anish singh wrote: > Hi Guenter, > > On Fri, May 31, 2013 at 3:32 AM, Guenter Roeck wrote: > > On Thu, May 30, 2013 at 11:59:28PM +0200, Wim Van Sebroeck wrote: > >> Hi Guenter, > >> > >> > On Tue, May 28, 2013 at 10:10:53AM +0200, Johannes Thumshirn wrote: > >> > > On Mon, May 27, 2013 at 08:25:54PM +0200, Wim Van Sebroeck wrote: > >> > > [...] > >> > > > > + watchdog_set_drvdata(&a21_wdt, drv); > >> > > > > >> > > > I am missing the initialisation of the watchdog's timeout value here... > >> > > > >> > > This watchdog only knows two timeout values, 1s and 30s with the constraint > >> > > that you can't go back to 30s once your in a 1s timeout without a reset of the > >> > > CPLD. I could initially set it to 30s but that would be redundant. > >> > > > >> > I wonder - why bother with supporting one-second timeouts ? > >> > > >> > Is this realistic, ie can you guarantee that the watchdog will be pinged fast > >> > enough to keep the system alive under all load conditions ? As far as I know > >> > you can not even configure the watchdog application for less than 1 second > >> > ping intervals. > >> > >> that's why certain drivers use a timer to keep kicking the watchdog at > >> a rate of 0.5s (do a grep on HZ/2) untill userspace times out. > >> (example: drivers/watchdog/pika_wdt.c or drivers/watchdog/pcwd.c). > >> > > Yes, I have used the same trick in a couple of my drivers. That isn't done here, > > though. > > > > I even thought about adding this capability to the infrastructure. > > If you don't mind can I give it a try? I don't mind, but you might want to wait for Wim's feedback. Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/