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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D6E6C433F5 for ; Mon, 31 Jan 2022 16:32:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349947AbiAaQct (ORCPT ); Mon, 31 Jan 2022 11:32:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350040AbiAaQcs (ORCPT ); Mon, 31 Jan 2022 11:32:48 -0500 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8165CC06173D for ; Mon, 31 Jan 2022 08:32:48 -0800 (PST) Received: by mail-pf1-x42e.google.com with SMTP id i30so13293148pfk.8 for ; Mon, 31 Jan 2022 08:32:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=jrmCnw1vWbPG3vz+B6LPTNIGeWcQyoJjyMn1cPywoW0=; b=BLDLfU5xiPEST4k+7rKwaIBto82ggkKMBj1VsQuz/7WQj5EDZjJBX1DvXVtJ/OQ/Re WcanpYChyFlDDySnX/x7z0hs7Kqu5V94fwNk8cGdwLAs/YkyL0Syt+mDvv+MQTyuOfeH uLCvHWyYZZ7+1SAJC1CSGdkFTxkyK+09724WME18Abdl+pNoxgNjgj53Krx/7z/zKwPT aRehDxttuSsbWTGFbeZojvukKZy2FvkX8b5hf7KVaL/0uGCi2FMSllHNmSiRVhxj0wbP uJ17BKJSC+eNkMXqjmtejlKYZGVL4WqWYRK/UAeuTy4C5tNOvoahGKD7PFpy5fTwxEhg /9+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=jrmCnw1vWbPG3vz+B6LPTNIGeWcQyoJjyMn1cPywoW0=; b=dT6DP4gTUlEqQ/iGAo3B5aGhSpssCv+OPs0V8NDGvfAOq9q2Hcx+Z9NfMBkkEMqtoc TEac/xvGzzzgEWH7iifb8xEA0ZGm3t7Y/lbSW8ABwE5/BZIg6tjxTKQRGgrIfm7UpXEC SAQKvw2p6u+hOK1SDO/BXpzT7xJIXln6rhnvtNzriRTCOO6k16ekQI9l+9BmivEllHSJ WUzRDojH63UD2ocRyxUypNCPtgDACaqJw52ueAMM4oNXeRM9Z5z/rSnQIDAZFMrbDGiU cRTrIFQT+CmnsSM4K8hhrUNInb07dw8QGt08SiW20b9s0j3hNtKxT5Nxb5Sayn4TYyzv hyIg== X-Gm-Message-State: AOAM532e5Y4yoYSh8CRK/R7cK1MOgDkPbiwP+I0NnnzAAzyOlTTDfbYI vVtmdZjhIsGgS2RsyIcShZk6MkOzeoc= X-Google-Smtp-Source: ABdhPJxWeAOFqTFc1z6NDk7dS2Nx647umStBvyoKiHvQ4bh+44xt9UND9STECbjrqP4BCkv73CVfKA== X-Received: by 2002:a63:f942:: with SMTP id q2mr17500139pgk.573.1643646767996; Mon, 31 Jan 2022 08:32:47 -0800 (PST) Received: from hoboy.vegasvil.org ([2601:640:8200:33:e2d5:5eff:fea5:802f]) by smtp.gmail.com with ESMTPSA id nl12sm12999194pjb.1.2022.01.31.08.32.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Jan 2022 08:32:47 -0800 (PST) Date: Mon, 31 Jan 2022 08:32:40 -0800 From: Richard Cochran To: Miroslav Lichvar Cc: netdev@vger.kernel.org, Yangbo Lu Subject: Re: [PATCH net-next 5/5] ptp: start virtual clocks at current system time. Message-ID: <20220131163240.GA22495@hoboy.vegasvil.org> References: <20220127114536.1121765-1-mlichvar@redhat.com> <20220127114536.1121765-6-mlichvar@redhat.com> <20220127220116.GB26514@hoboy.vegasvil.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jan 31, 2022 at 11:21:08AM +0100, Miroslav Lichvar wrote: > I tried to find the discussion around this decision, but failed. Do > you have a link? I'll dig it up for you. > To me, it seems very strange to start the PHC at 0. It makes the > initial clock correction unnecessarily larger by ~7 orders of > magnitude. The system clock is initialized from the RTC, which can > have an error comparable to the TAI-UTC offset, especially if the > machine was turned off for a longer period of time, so why not > initialize the PHC from the system time? The error is much smaller > than billions of seconds. When the clock reads Jan 1, 1970, then that is clearly wrong, and so a user might suspect that it is uninititalized. When the clock is off by 37 seconds, the user will likely post a vague complaint to linuxptp-users asking why linuxptp doesn't handle leap seconds. I prefer the clarity of the first case. Thanks, Richard