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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9724C4727D for ; Tue, 6 Oct 2020 14:01:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D2A52083B for ; Tue, 6 Oct 2020 14:01:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Yxt7ComH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726060AbgJFOBI (ORCPT ); Tue, 6 Oct 2020 10:01:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59500 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725939AbgJFOBH (ORCPT ); Tue, 6 Oct 2020 10:01:07 -0400 Received: from mail-ed1-x543.google.com (mail-ed1-x543.google.com [IPv6:2a00:1450:4864:20::543]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B4C2C061755; Tue, 6 Oct 2020 07:01:07 -0700 (PDT) Received: by mail-ed1-x543.google.com with SMTP id 33so13647639edq.13; Tue, 06 Oct 2020 07:01:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=pWzTzItFMGquZ9N6WRVzwFoGPMpIgrJK7QQeAOkDiPE=; b=Yxt7ComHPrYsEFGeYm918+o3bwnCYsjcgk/G6HNF9NtX3L1Be3zoVtXMtuZ9E46qkw h+knokkUfc+05uRrFfdNXJGgGxN2sHUsFMdwY6HPR/H1Mkj6Yc5fhbrTBOTPSAKb0GNd y8BY1FAzP3jyKZb4eKZIIF2tjJkfx/hm7njK3e5fP5mtKmUb+JerlYtc7tVVWqOZvuhR zlAQHAAXZjUNtUYfv9GBJK+987Rtcx89WFPdsHcSKps6jNfkd8m/plTt+A+rzr4DDFE0 p1cBYuOrBhtFwSUEiLur+LEMYHIvqsNMJGSjaCpJlAWwfbHUrwAykOEdVz9B7+Qzv8ZP GF/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=pWzTzItFMGquZ9N6WRVzwFoGPMpIgrJK7QQeAOkDiPE=; b=sQPTeQbbx4eL2mljgBBfQfhhxJ1UVcDZbvVQu+5NV6naLuVCiNtKSElk6tR60wcsDG FqqTWar/x0pQHXQzPzuU8UBI6/FoMdlesjhGiQqHWAMvwHOKPTkUjqcmnj0ml8+11npX iSUv8f934UUxgut+bsr9c0rjwm5vIltIlLVdL9LOkHAuagxY7laUEbLr2hIvHNZbIa5q ySYIDQ37p0v1nhFx8eGMwuH56sMzv3f49FrWDFfVGaqsKy9h2qDRrkG9FV9EkwhbhW6n 8Hy+ddWpyGjYo/k0ZEVag1NOtcIbTPgjPmC07weYSjhUpcbVOuexB0wjG5hTGVngXHqC 038A== X-Gm-Message-State: AOAM532havSQDE4+elomkvMhr0a+0lQbIc60ENiZrKAQLFlXYg7IeysW VQGhDGgPt4zrTX7FBjjIypE= X-Google-Smtp-Source: ABdhPJwnCMo0DagOwfhno9ZjV6kDRoNM/laQzOuhcaRPEJTDc8rVkskaQzz/lCaZjd82Ne1NppuB3Q== X-Received: by 2002:a05:6402:709:: with SMTP id w9mr5552917edx.326.1601992865873; Tue, 06 Oct 2020 07:01:05 -0700 (PDT) Received: from skbuf ([188.26.229.171]) by smtp.gmail.com with ESMTPSA id q1sm2284655ejy.37.2020.10.06.07.01.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Oct 2020 07:01:04 -0700 (PDT) Date: Tue, 6 Oct 2020 17:01:02 +0300 From: Vladimir Oltean To: Kurt Kanzenbach Cc: Andrew Lunn , Vivien Didelot , Florian Fainelli , "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org, Rob Herring , devicetree@vger.kernel.org, Sebastian Andrzej Siewior , Richard Cochran , Kamil Alkhouri , ilias.apalodimas@linaro.org Subject: Re: [PATCH net-next v6 4/7] net: dsa: hellcreek: Add support for hardware timestamping Message-ID: <20201006140102.6q7ep2w62jnilb22@skbuf> References: <20201004112911.25085-1-kurt@linutronix.de> <20201004112911.25085-5-kurt@linutronix.de> <20201004143000.blb3uxq3kwr6zp3z@skbuf> <87imbn98dd.fsf@kurt> <20201006072847.pjygwwtgq72ghsiq@skbuf> <87tuv77a83.fsf@kurt> <20201006133222.74w3r2jwwhq5uop5@skbuf> <87r1qb790w.fsf@kurt> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r1qb790w.fsf@kurt> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Oct 06, 2020 at 03:56:31PM +0200, Kurt Kanzenbach wrote: > On Tue Oct 06 2020, Vladimir Oltean wrote: > > On Tue, Oct 06, 2020 at 03:30:36PM +0200, Kurt Kanzenbach wrote: > >> That's the point. The user (or anybody else) cannot disable hardware > >> stamping, because it is always performed. So, why should it be allowed > >> to disable it even when it cannot be disabled? > > > > Because your driver's user can attach a PTP PHY to your switch port, and > > the network stack doesn't support multiple TX timestamps attached to the > > same skb. They'll want the TX timestamp from the PHY and not from your > > switch. > > Yeah, sure. That use case makes sense. What's the problem exactly? The SO_TIMESTAMPING / SO_TIMESTAMPNS cmsg socket API simply doesn't have any sort of identification for a hardware TX timestamp (where it came from). So when you'll poll for TX timestamps, you'll receive a TX timestamp from the PHY and another one from the switch, and those will be in a race with one another, so you won't know which one is which.