From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752347AbZH0MJJ (ORCPT ); Thu, 27 Aug 2009 08:09:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752315AbZH0MJH (ORCPT ); Thu, 27 Aug 2009 08:09:07 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:54634 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752303AbZH0MJD (ORCPT ); Thu, 27 Aug 2009 08:09:03 -0400 Date: Thu, 27 Aug 2009 08:08:41 -0400 From: Josh Boyer To: Wim Van Sebroeck Cc: Chris Friesen , linuxppc-dev@ozlabs.org, Linux kernel Subject: Re: [PATCH] fix book E watchdog to take WDIOC_SETTIMEOUT arg in seconds Message-ID: <20090827120841.GA25303@zod.rchland.ibm.com> References: <4A8303C6.7070705@nortel.com> <20090827111458.GB29382@infomag.iguana.be> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090827111458.GB29382@infomag.iguana.be> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 27, 2009 at 01:14:58PM +0200, Wim Van Sebroeck wrote: >Hi Chris, > >> The WDIOC_SETTIMEOUT argument is supposed to be a "seconds" value. >> However, the book E wdt currently treats it as a "period" which is >> interpreted in a board-specific way. >> >> This patch allows the user to pass in a "seconds" value and the driver >> will set the smallest timeout that is at least as large as specified >> by the user. It's been tested on e500 hardware and works as >> expected. >> >> The patch only modifies the CONFIG_FSL_BOOKE case, the CONFIG_4xx case >> is left unmodified as I don't have any hardware to test it on. >> >> Signed-off-by: Chris Friesen > >Added with some small changes to keep checkpatch happy. (removed trailing spaces + changed sizeof(struct watchdog_info) to sizeof(ident) and changed some spaces in tabs). > >Now we only need someone that can look at the CONFIG_4xx cases still :-) It seems the FSL watchdog is much more flexible than the one found in 4xx cores. On 4xx, you basically have 4 static choices that represent specific times determined by the clock frequency. I'm concerned that the lack of granularity here will result in less than desirable behavior. For example, with a 400MHz clock you would get choices of roughly: 5.2 ms 83.9 ms 1.34 s 21.47 s Personally, I consider the first two options basically unusable. Considering the second two, if a user were to say "Set the timeout for 2 seconds" they would then get a timeout of 21 seconds with the framework Chris' patch has set up. That doesn't really seem to be ideal to me. josh