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 3EAF3C433EF for ; Thu, 7 Apr 2022 09:44:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243975AbiDGJqp (ORCPT ); Thu, 7 Apr 2022 05:46:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243974AbiDGJqm (ORCPT ); Thu, 7 Apr 2022 05:46:42 -0400 Received: from mail-ed1-x530.google.com (mail-ed1-x530.google.com [IPv6:2a00:1450:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A79CB213507 for ; Thu, 7 Apr 2022 02:44:42 -0700 (PDT) Received: by mail-ed1-x530.google.com with SMTP id q26so5712694edc.7 for ; Thu, 07 Apr 2022 02:44:42 -0700 (PDT) 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; bh=DkggEoH1Cy9Q4wekLlHSimO5P2kOetKNoD/TtD4Swy4=; b=OIG9QYF1N23IWQlJKss15z7ZfI3zRRClxcMApD9yHcs+hyWr9NwlxxX4Zsln6q0C5p QYUG43RA1xSGOm+z0xFQdcBQY+ScaEDt3pNzzSW0UPWY+9u90AMHohXJbQfQZaoizsO+ snPSxt0908hyk+pHem1V3ziix0WQnkSD5kFrgEn1cTcGk1hLbCjHa2r6CPJIgo0lORGm 2NyvVusYJMiCTyv37+Oeuld2o0coEcfDMbz5vfSpiR6afkhhtfs7w7Bvw8LeqN35v3vI RYxy8mP5iQYmq1ZnCnyGPAb30sazkFwFzen8uylGRTL7YlC2nhNKkhnI/BRz6sQh9e39 0jTQ== 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; bh=DkggEoH1Cy9Q4wekLlHSimO5P2kOetKNoD/TtD4Swy4=; b=0pbxrk5XdhRhg5V61cfbVHqOjzFRROc9Z497aouCGi6UNF16OS0x2TUsAL6G9LOQru uViDEnlA1DHn6Npxk5DVp6dBlHyBypgeUXoUuX7fhfop7drtpmitXAbvY0cM71Gl9RMG eoBYNcXRCNU9xdsx9mZ0YXM5V+BZSqKsoJrsjTanJVko1xRELCos4BVs96evmnL7MGcV 9esI4oPKnOzh893c0QStIENI0QLEH0bsqUc9+4NC+BeKu2yrW19RVHvOsqPKll/aOQHt AQ8RB85G2BHcx/BkzZOqLMXS3wJ5hrs/uYqERzt8ibyQ4CqHKwkCSgy1bLhjlfYYE+JN b4gQ== X-Gm-Message-State: AOAM5302QRhXUDm28GQXwCQtKiIXeLy/ZepETfMIO6rjDpslGW23q6TZ v/wdy/utoeVjVLdqz7GDvY0= X-Google-Smtp-Source: ABdhPJx8R8skSLzDlT9e6iyhsVIETvIMK4+84/ZvCBSDMMDEO6cgui4YUpWcpi7vVxJyYuFpO5eeNA== X-Received: by 2002:a05:6402:50c9:b0:419:3019:2d35 with SMTP id h9-20020a05640250c900b0041930192d35mr13296027edb.95.1649324680995; Thu, 07 Apr 2022 02:44:40 -0700 (PDT) Received: from skbuf ([188.26.57.45]) by smtp.gmail.com with ESMTPSA id e9-20020a50e009000000b0041cd2e38a3bsm5245799edl.81.2022.04.07.02.44.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Apr 2022 02:44:40 -0700 (PDT) Date: Thu, 7 Apr 2022 12:44:39 +0300 From: Vladimir Oltean To: Jakub Kicinski Cc: Andrew Lunn , Matej Zachar , netdev@vger.kernel.org Subject: Re: [DSA] fallback PTP to master port when switch does not support it Message-ID: <20220407094439.ubf66iei3wgimx7d@skbuf> References: <25688175-1039-44C7-A57E-EB93527B1615@gmail.com> <20220405124851.38fb977d@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220405124851.38fb977d@kernel.org> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Apr 05, 2022 at 12:48:51PM -0700, Jakub Kicinski wrote: > On Tue, 5 Apr 2022 00:04:30 +0200 Andrew Lunn wrote: > > What i don't like about your proposed fallback is that it gives the > > impression the slave ports actually support PTP, when they do not. > > +1, running PTP on the master means there is a non-PTP-aware switch > in the path, which should not be taken lightly. +2, the change could probably be technically done, and there are aspects worth discussing, but the goal presented here is questionable and it's best to not fool ourselves into thinking that the variable queuing delays of the switch are taken into account when reporting the timestamps, which they aren't. I think that by the time you realize that you need PTP hardware timestamping on switch ports but you have a PTP-unaware switch integrated *into* your system, you need to go back to the drawing board.