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 ACD19C4332F for ; Tue, 8 Mar 2022 18:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349408AbiCHSLS (ORCPT ); Tue, 8 Mar 2022 13:11:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242020AbiCHSLQ (ORCPT ); Tue, 8 Mar 2022 13:11:16 -0500 Received: from vps0.lunn.ch (vps0.lunn.ch [185.16.172.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A0C65642C; Tue, 8 Mar 2022 10:10:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=1eP4QAP4khvsw420Ab+eccOZXeXGnoYv+vACX02zlWA=; b=Iwc5+pUND40BrxDXOYvWaSuZRZ 4S9vforAtlBDJ+g1pAXfy+j38KA7GsQwG0iifQKDRtPnbi0oD4HR3rIq5B8sxsR1GkSfKaZJRJ4rd vvz4gFT9JsX/Fy7HKjPJqxV2VILd2kCdqkikmER3y3eFtzP+Ia0sD30LNW8ax1HeFbss=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1nReHk-009q5y-58; Tue, 08 Mar 2022 19:10:12 +0100 Date: Tue, 8 Mar 2022 19:10:12 +0100 From: Andrew Lunn To: Horatiu Vultur Cc: 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, richardcochran@gmail.com, 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: References: <20220304093418.31645-1-Divya.Koppera@microchip.com> <20220304093418.31645-3-Divya.Koppera@microchip.com> <20220308154345.l4mk2oab4u5ydn5r@soft-dev3-1.localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220308154345.l4mk2oab4u5ydn5r@soft-dev3-1.localhost> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > So this is a function of the track length between the MAC and the PHY? > > Nope. > This latency represents the time it takes for the frame to travel from RJ45 > module to the timestamping unit inside the PHY. To be more precisely, > the timestamping unit will do the timestamp when it detects the end of > the start of the frame. So it represents the time from when the frame > reaches the RJ45 to when the end of start of the frame reaches the > timestamping unit inside the PHY. I must be missing something here. How do you measure the latency difference for a 1 meter cable vs a 100m cable? Does 100m cable plus 1cm of track from the RJ45 to the PHY make a difference compared to 100m cable plus 1.5cm of track? Isn't this error all just in the noise? Andrew