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 84096C433EF for ; Wed, 9 Mar 2022 01:58:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231268AbiCIB7n (ORCPT ); Tue, 8 Mar 2022 20:59:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231279AbiCIB7m (ORCPT ); Tue, 8 Mar 2022 20:59:42 -0500 Received: from mail-pf1-x429.google.com (mail-pf1-x429.google.com [IPv6:2607:f8b0:4864:20::429]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 338394CD4B; Tue, 8 Mar 2022 17:58:45 -0800 (PST) Received: by mail-pf1-x429.google.com with SMTP id z15so960052pfe.7; Tue, 08 Mar 2022 17:58:45 -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=7PG7n6GhwgZymh0wA6094FxRWkefaowHSSxuvDcjabc=; b=R91Qwwy0Cb0xukbPogn0xW4aYwy2Aqq1sxGWvw2CcvjTxDoKHGR6y8lGWPpmwAYGXX 0iQIC1YFr0y4ysF43dyTH5hXZbRKxHcXhi4aqNBgX2FdjLtIKn+mZzycbEBe1JZnZoIA tf33wNOcZnhzcBow2xFkB9H7E39ew4sQTNwHz/0PxxsGlyqxF8/SPnfUVKgImxPyic1H caYSjl+/k5sULbq3iwmVZ55qNuSchLni6l9HbNd5aVqxCKwUm9QHaWEKHtrHQzMds3Tw J45+Y/7O/QrY5T6ovlIl64qnJWr7Wg6Qm5EPNY4MfUp5pRRE+6XJTtIanW7UNZrd+JnP 3Y6Q== 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=7PG7n6GhwgZymh0wA6094FxRWkefaowHSSxuvDcjabc=; b=Z8YMhUMFzlNADUqpvxHuIFqJ/UmPO2uhGqVPc9id02MJi3N4F0NqqimdDA+Kgh0Scg ohr95peE7eUMaf4lBLZcAszie6X4Fk5hxFa0tdZf0dL0w04JEtNta8VSHTAV01Tig1BT zDZ6Z7Eg+142l9JlK/rFiXJKTFDEEy5weAQeURY45usHEgZkJQvRcEhPbZDeENKdFRJN rolf3ImPUoCo1ifNSKXE5iw5/IPE7uA4fZ9ZL/DqTdyT4PF+e1T1hoCjXMfp/sPamXsB EQGohXYEBpyawL34pQ1Pm12pZaTp3HWCNI9Iw38HYniHDtMAavKcmSwP4z1bmejpfWOH e2Uw== X-Gm-Message-State: AOAM530rr5qSfU96TSvMXDgL7CpSMMoGeSmLLzkZz+/VtqbGnJiI2PeP hycN7UPLE3rMUulXFcYQ9GA= X-Google-Smtp-Source: ABdhPJzJjgOdKTS8G8Lg4WHgrtnaFnKyVgFZgmCMHdFTAsAdtEUV0ecvjEho8Jsy2RKPy26VWbwXsQ== X-Received: by 2002:a05:6a00:1152:b0:4be:ab79:fcfa with SMTP id b18-20020a056a00115200b004beab79fcfamr20964596pfm.3.1646791124720; Tue, 08 Mar 2022 17:58:44 -0800 (PST) Received: from hoboy.vegasvil.org ([2601:640:8200:33:e2d5:5eff:fea5:802f]) by smtp.gmail.com with ESMTPSA id b1-20020a630c01000000b003758d1a40easm371184pgl.19.2022.03.08.17.58.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Mar 2022 17:58:44 -0800 (PST) Date: Tue, 8 Mar 2022 17:58:41 -0800 From: Richard Cochran To: Andrew Lunn Cc: Horatiu Vultur , Divya.Koppera@microchip.com, netdev@vger.kernel.org, hkallweit1@gmail.com, linux@armlinux.org.uk, davem@davemloft.net, kuba@kernel.org, robh+dt@kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, UNGLinuxDriver@microchip.com, Madhuri.Sripada@microchip.com, Manohar.Puri@microchip.com Subject: Re: [PATCH net-next 2/3] dt-bindings: net: micrel: Configure latency values and timestamping check for LAN8814 phy Message-ID: <20220309015841.GC24366@hoboy.vegasvil.org> References: <20220308154345.l4mk2oab4u5ydn5r@soft-dev3-1.localhost> <20220308221404.bwhujvsdp253t4g3@soft-dev3-1.localhost> <20220309014647.GB24366@hoboy.vegasvil.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220309014647.GB24366@hoboy.vegasvil.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, Mar 08, 2022 at 05:46:47PM -0800, Richard Cochran wrote: > The problem with uncorrected PHY time stamps is that they affect the > boundary point between the node and the network. A static error there > will create a path asymmetry that can neither be measured nor > corrected by the PTP, and a variable error degrades the time signal. And FWIW, the imperfections in the cable *also* introduce path asymmetry and thus uncorrected offsets. The twisted pairs are never exactly the same length in both directions, for example. However the PHY delays can be in the microseconds, but cable delay deltas in the nanoseconds, so correcting PHY delay is much more important. Thanks, Richard