From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE14BC4363C for ; Wed, 7 Oct 2020 11:04:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7627820870 for ; Wed, 7 Oct 2020 11:04:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="nTsTEOYy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728003AbgJGLE2 (ORCPT ); Wed, 7 Oct 2020 07:04:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727278AbgJGLE2 (ORCPT ); Wed, 7 Oct 2020 07:04:28 -0400 Received: from mail-oo1-xc44.google.com (mail-oo1-xc44.google.com [IPv6:2607:f8b0:4864:20::c44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66825C061755; Wed, 7 Oct 2020 04:04:27 -0700 (PDT) Received: by mail-oo1-xc44.google.com with SMTP id b12so489341oop.13; Wed, 07 Oct 2020 04:04:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:subject:to:cc:references:from:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=1ymvn+cxkMCxMYqq3wm6zoSqMltLe0LOv9Gk+3UzRlw=; b=nTsTEOYyMWDvbLVhAJ1vmhc5uc/KiwqgqlGIuvCsxZQSqDuSti+h+EZsCaCGIBfrCW vY/VVNVklO2e1gZzy3+1rvSKUWwRjHyF4w11jfT+Af/LnxRm3t0QAt2YMVU2K4tOTqGn bJi40nKI3PrUe//EQZG0OBYW7YNhV9pbdSnG+bCWFSXJzIMBdflwgBzOCj+xTln+vjnU NjU1fyaS5kLfvGEXRRI+SkjBIOky4be7y5M0xJg14efz/U3F1YAWB0d1pAyvZ4ucaVO3 V1ZwYOiNyFyr/lJVWHnhNhmlMSRuifQEnNHA5SRMhpbn95JG9ri2UzQVWhDpyrJ3nrMd db5A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=1ymvn+cxkMCxMYqq3wm6zoSqMltLe0LOv9Gk+3UzRlw=; b=HBKFFNXUqVpiRlRu4T5FVk8616Y162Df4TUZl86AiZCyxwrJGIIafo1ss64KQ/0kFJ nd1s2FTXQxCswN8+aEdzQCCWCd+aXi3edHl2EefUr2SqfuE6ZJidQV5O+RniOkXbCvlR ZwMZqZbLr+96mSl4q9Ma5z7K1kAKHh1Spfuc9jJNHIS61BBJ8wQ8JHuhYqtLXHrku5pl x0XEZv6amiaHT3Z73oMwRVM4hQCBWh+7fpZwY7K5PhuJ9oZsTrv7PLmPlnixCE7wdLtx tY1bg1yjKgGClm1fMQyvYyupMrxNf0B+XVvqvjNxNpAYLZU9rcAlZFpaPct4oz5HtcIL soxw== X-Gm-Message-State: AOAM533S0mVdz5HkJLMw+N7bOYMapG0jSxCJzopn0xidM6tNEA8PXx29 BQBAS1/DhtT63ce5NtEmTnmyquGiI9Y= X-Google-Smtp-Source: ABdhPJwDZw7JffZYdib9ML6Cd1+kBHuBA4PMTzFg2qPml4R9jvSaKCEN1GZW/203a7unvszDSa6gWg== X-Received: by 2002:a4a:e544:: with SMTP id s4mr1701634oot.74.1602068666610; Wed, 07 Oct 2020 04:04:26 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id y10sm1870925oot.46.2020.10.07.04.04.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Oct 2020 04:04:25 -0700 (PDT) Sender: Guenter Roeck Subject: Re: dt-binding to define default watchdog and machine reset (Was: Re: [RFC] Using a watchdog as system reset) To: =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= , Ahmad Fatoum , Rob Herring Cc: devicetree@vger.kernel.org, linux-watchdog@vger.kernel.org, kernel@pengutronix.de, Wim Van Sebroeck , Frank Rowand References: <20201006102949.dbw6b2mrgt2ltgpw@pengutronix.de> <460aa962-9da5-6e1e-b5db-3f9f1d78110a@roeck-us.net> <41b0dfcd-adf1-296f-e5be-4db3eac9f097@roeck-us.net> <20201006184130.r2lajves5l7lm2qk@pengutronix.de> <20201007071222.pnftcuezlricotq3@pengutronix.de> <04e33d49-4210-9dcd-040c-35059e0619ba@pengutronix.de> <20201007101835.yhlbjfpklepfodgw@pengutronix.de> From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= Message-ID: <7e6dd4f6-cc1d-c7c8-4e56-5239995c4e87@roeck-us.net> Date: Wed, 7 Oct 2020 04:04:24 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201007101835.yhlbjfpklepfodgw@pengutronix.de> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 10/7/20 3:18 AM, Uwe Kleine-König wrote: > Hello, > > [promoted Rob from Cc: to To: and adapted the subject in the hope to get > some feedback] > > On Wed, Oct 07, 2020 at 09:25:30AM +0200, Ahmad Fatoum wrote: >> On 10/7/20 9:12 AM, Uwe Kleine-König wrote: >>> On Tue, Oct 06, 2020 at 02:04:10PM -0700, Guenter Roeck wrote: >>>> With that in mind, your other option kind of makes sense. The only >>>> question would be how to express this in devicetree. I am certainly >>>> open to accepting a patch introducing such a property/functionality >>>> into the watchdog core. >>> >>> OK, will try to come up with a patch. >> >> Instead of having a `provide-system-reset' property, how about providing >> it unconditionally, but with a very low priority? >> Personally I don't think that would be a good idea, first in general but also because the generic restart handling mechanism is still not universally used (the last five or so patches needed to make it complete have been blocked by various people each time they were submitted, so we can be sure that they will never be accepted). Also, you would have to have a means to disable it, which would be equivalent to having a means to enable it, so making it enabled by default seems pointless and would unnecessarily introduce potential problems. >> This can be coupled with Guenther's suggestion of having a dynamic >> way to set the priority, e.g. a `watchdog-priority' property in the device >> tree that's common to all watchdogs? That's the way barebox is handling >> multiple watchdogs (default value in driver overridable in DT and at runtime). > > OK, I'll try to put this in more verbose words: > > Let's introduce a generic watchdog property `watchdog-priority' that > provides a u32 to order the watchdogs for systems having two or more. > The value 0 means the watchdog is unusable/broken/disabled and the > watchdog with the biggest value is the one supposed to be used by > default. > How do you suggest to implement that ? Device naming is determined by registration order. The watchdog subsystem doesn't decide which of the watchdogs is being used; userspace does that by opening the watchdog device. Userspace can already decide which watchdog to use by checking its sysfs attributes. If we were to create a sysfs attribute for userspace to read and compare, userspace could as well use the existing 'identity' attribute to make that decision. > Analogous a property `watchdog-restart-priority` is used to define if a > watchdog is supposed to be used to restart the machine. Again a value of > 0 means "Don't use" and otherwise the highest-value watchdog is used to > reset the machine. > That makes more sense to me. Guenter > Maybe `restart-priority` is a better name that can also be used by > PMICs?! > >> What's the DT folks opinion on that? > > Best regards > Uwe >