Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933613AbbFJRyc (ORCPT ); Wed, 10 Jun 2015 13:54:32 -0400 Received: from mail-oi0-f52.google.com ([209.85.218.52]:34963 "EHLO mail-oi0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754405AbbFJRyX (ORCPT ); Wed, 10 Jun 2015 13:54:23 -0400 MIME-Version: 1.0 In-Reply-To: References: <=fu.wei@linaro.org> <1433217907-928-1-git-send-email-fu.wei@linaro.org> <1433217907-928-6-git-send-email-fu.wei@linaro.org> <556DCC95.806@codeaurora.org> <556DE2D5.3090906@roeck-us.net> <5575DE48.8010308@roeck-us.net> <55766D74.2060401@roeck-us.net> <55769E0E.8060801@roeck-us.net> <557712CF.8010802@roeck-us.net> <5577147B.2030900@codeaurora.org> <5577180E.4070804@roeck-us.net> Date: Thu, 11 Jun 2015 01:54:22 +0800 Message-ID: Subject: Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver From: Fu Wei To: Guenter Roeck Cc: Timur Tabi , Suravee Suthikulpanit , Linaro ACPI Mailman List , linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Wei Fu , G Gregory , Al Stone , Hanjun Guo , Ashwin Chaugule , Arnd Bergmann , Vipul Gandhi , Wim Van Sebroeck , Jon Masters , Leo Duran , Jon Corbet , Mark Rutland , Catalin Marinas , Will Deacon , rjw@rjwysocki.net Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3866 Lines: 125 Hi Guenter, On 10 June 2015 at 23:38, Fu Wei wrote: > Hi Guenter, > > > On 10 June 2015 at 11:41, Fu Wei wrote: >> Hi Guenter, >> >> On 10 June 2015 at 00:45, Guenter Roeck wrote: >>> On 06/09/2015 09:29 AM, Timur Tabi wrote: >>>> >>>> On 06/09/2015 11:22 AM, Guenter Roeck wrote: >>>>> >>>>> >>>>> >>>>> but I see your point. Essentially, the specification is broken >>>>> for all practical purposes, since, as you point out, enabling >>>>> the watchdog overwrites and explicitly sets WCV. Effectively >>>>> this means that just using WCV to program the timeout period >>>>> is not really possible. >>>>> >>>>> I am not really sure how to address this. We can either only use WOR, >>>>> and forget about pretimeout, or we can enforce a minimum pretimeout. >>>>> In the latter case, we'll have to write WCV after writing WOR. >>>> >>>> >>>> In talking with our hardware engineers, using WCV to program the timeout >>>> period is not a valid operation. This is why I keep arguing against the >>>> pre-timeout feature, and I don't agree that servers should always use >>>> pre-timeout. >>>> >>> >>> Not sure if "not valid" is correct - after all, it is mentioned in the >>> specification. However, it is at the very least fragile. >> >> I think we should focus on SBSA spec, but not a specific chip design, >> because this is SBSA watchdog, not a driver for an IP core from a >> specific chip vendor. >> this operation is mentioned in the spec, >> and I have tested my driver on Foundation model(from ARM) and a real hardware. >> >>> >>> I tend to agree that we should just forget about pretimeout and >>> use your original approach, where the timeout value is used >>> to program WOR. Everything else is really just asking for trouble. >> >> I don't mind if we give up pretimeout, The reason I use pretimeout is: >> this concept matches the function of two stage timeouts. >> >> but, If we give up pretimeout, could you give me a suggestion: >> >> How to config the two stage timeouts >> (1)from enabling watchdog to WS0 >> (2)the time from WS1 to WS0 >> >> If we only have one timeout parameter, How to config the two stage timeouts? >> Any suggestion ? > > I have another thought for this, please allow me to sent anther > patchset in a day. see if you like it. I have sent a non-pretimeout version patchset, please let me know if you like the non-pretimeout version more. Great thanks for your time. :-) > >> >> If we make the first stage timeout is timeout/2, this violates the >> definition of timeout. >> I don't think users expect interrupt, panic or reboot at timeout/2. >> >> And WS1 definitely isn't a backup of WS0. >> >>> >>> Guenter >>> >> >> >> >> -- >> Best regards, >> >> Fu Wei >> Software Engineer >> Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch >> Ph: +86 21 61221326(direct) >> Ph: +86 186 2020 4684 (mobile) >> Room 1512, Regus One Corporate Avenue,Level 15, >> One Corporate Avenue,222 Hubin Road,Huangpu District, >> Shanghai,China 200021 > > > > -- > Best regards, > > Fu Wei > Software Engineer > Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch > Ph: +86 21 61221326(direct) > Ph: +86 186 2020 4684 (mobile) > Room 1512, Regus One Corporate Avenue,Level 15, > One Corporate Avenue,222 Hubin Road,Huangpu District, > Shanghai,China 200021 -- Best regards, Fu Wei Software Engineer Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch Ph: +86 21 61221326(direct) Ph: +86 186 2020 4684 (mobile) Room 1512, Regus One Corporate Avenue,Level 15, One Corporate Avenue,222 Hubin Road,Huangpu District, Shanghai,China 200021 -- 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/