From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752936Ab3LBGOZ (ORCPT ); Mon, 2 Dec 2013 01:14:25 -0500 Received: from mail-out.m-online.net ([212.18.0.9]:42709 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751179Ab3LBGOX (ORCPT ); Mon, 2 Dec 2013 01:14:23 -0500 X-Auth-Info: Qg7j/7oJp9XJjFxK15kPu3oh7CUqrkDboxrF3uMfqz8= To: Guenter Roeck cc: Christophe Leroy , Wim Van Sebroeck , scottwood@freescale.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org From: Wolfgang Denk Subject: Re: [PATCH] watchdog: mpc8xxx_wdt: MPC8xx is HW enabled MIME-Version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 8bit In-reply-to: <529B9152.9090106@roeck-us.net> References: <20131130154540.E83D743E15@localhost.localdomain> <529B9152.9090106@roeck-us.net> Comments: In-reply-to Guenter Roeck message dated "Sun, 01 Dec 2013 11:43:14 -0800." Date: Mon, 02 Dec 2013 07:14:17 +0100 Message-Id: <20131202061418.05A11380BFE@gemini.denx.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dear Guenter, In message <529B9152.9090106@roeck-us.net> you wrote: > On 11/30/2013 07:45 AM, Christophe Leroy wrote: > > MPC8xx watchdog is enabled at startup by HW. > > If the bootloader disables it, it cannot be reenabled. > > Is that true for all variants of 8xx, especially for 823 ? I am a bit concerned > about breaking compatibility with some chips ... assuming there was a reason > for not setting this flag originally. This is correct, and applies for all variants of the MPC8xx, including the MPC823 / MPC823E. From the UM: "The software watchdog timer can be disabled or its timeout period can be changed in the SYPCR. Once the SYPCR is written, it cannot be written again until a system reset." Actually this is the only correct behaviour. Any watchdog that can be disabled by software is not worth it's name, and unsuitable for any kind of aplications where security / reliability are required. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de Ninety-Ninety Rule of Project Schedules: The first ninety percent of the task takes ninety percent of the time, and the last ten percent takes the other ninety percent.