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 D0EB1C433FE for ; Wed, 9 Mar 2022 01:46:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230486AbiCIBru (ORCPT ); Tue, 8 Mar 2022 20:47:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230473AbiCIBrt (ORCPT ); Tue, 8 Mar 2022 20:47:49 -0500 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A260847AD1; Tue, 8 Mar 2022 17:46:51 -0800 (PST) Received: by mail-pf1-x435.google.com with SMTP id a5so963833pfv.2; Tue, 08 Mar 2022 17:46:51 -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=B8bBqTwia7wBMwz5hHXZHCzqohNsptzJRrrGwkJNRS8=; b=nwj7tvDCQhT1tTSZYmeFh97v6ljyhYUeGt5xJaI5O+5JHeo06oneSZyrrLp9BGAYNI pMlEUKTuDpYeL6nlBXoq5WGC1p86052RqBGBeaop9vmCRbk8j+OE7kmswBlOQcWUZYqC ozkE/n0IsZrz/0oiZ1k+8RlL1lvSozFFqulT9DKNgIa3kEZU610qd8SVTBLtq01v3rmq Ces/SsF7xuWX4HjoBhGvS8jbozk85pviU83o6Yw1emBgHCO6Kw0O3HDB//5i7xHSKBRF vUQzWla11q3n6eixTOIm4NrDY5rPuED+sdh3H9ZqRREY9VP0fdsNZEEJtJH3avwR9DQA XYeg== 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=B8bBqTwia7wBMwz5hHXZHCzqohNsptzJRrrGwkJNRS8=; b=v0DdGmYv5HUPYgrQ987JVZi1+VnecA/G3OPbP8+uP9WcXUqv4e+a/cF+NaLNg7FoXu HgkAlND6stJBLAM0fJ31vPpU0mV3A74G39Zu/Pzt9mM7tS/RD+EoMjgy3BYPta9KSmVy OBH9nFNeFWPrU77mhop8SbvPgbnvfiWM1jwaHaQU6i2aM1Ir/ZlrZs9d/rzsiAzrxxsC uNqkNuDD7llikinHJ+97sf/hcel0zK5wra+m/WS2v604aMWej+cDSCKeK0FUBQV/CilI OQAzkT30M0jzu8BJbEB7btyLbccoxK1P4re03C3+0Yz0C6ZfaIn2W73F5ccgp8XsdqCs mffw== X-Gm-Message-State: AOAM533SasUcdPKCjpC1idsAGoxqEi0E9ylJ46lj10meD4XRj6hpIuxS FrChO2X6eftg9M2RyqnKQl+//7PABbk= X-Google-Smtp-Source: ABdhPJzjVo7e2qrmUbNkeL2htyp8gE3ptwnN+rocneGeMxNszSiqfQmZvPVecIgxWwjPCwx68Brb+g== X-Received: by 2002:a63:2bc1:0:b0:35e:c54b:3be0 with SMTP id r184-20020a632bc1000000b0035ec54b3be0mr16632074pgr.105.1646790411123; Tue, 08 Mar 2022 17:46:51 -0800 (PST) Received: from hoboy.vegasvil.org ([2601:640:8200:33:e2d5:5eff:fea5:802f]) by smtp.gmail.com with ESMTPSA id o185-20020a6341c2000000b0036fb987b25fsm358271pga.38.2022.03.08.17.46.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Mar 2022 17:46:50 -0800 (PST) Date: Tue, 8 Mar 2022 17:46:47 -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: <20220309014647.GB24366@hoboy.vegasvil.org> References: <20220304093418.31645-3-Divya.Koppera@microchip.com> <20220308154345.l4mk2oab4u5ydn5r@soft-dev3-1.localhost> <20220308221404.bwhujvsdp253t4g3@soft-dev3-1.localhost> 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 Wed, Mar 09, 2022 at 12:36:54AM +0100, Andrew Lunn wrote: > I'm assuming the ptp protocol does not try to measure the cable delay, > since if it did, there would be no need to know the RJ45-PHY delay, it > would be part of that. The PTP does indeed measure the cable delay. With a well tuned system, you can tell the copper cable length directly from the measured delay. 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. Thanks, Richard