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=-5.6 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, USER_AGENT_SANE_1 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 9EF28C433E0 for ; Mon, 13 Jul 2020 15:38:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D93220773 for ; Mon, 13 Jul 2020 15:38:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="A+JNrFxp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729806AbgGMPif (ORCPT ); Mon, 13 Jul 2020 11:38:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729703AbgGMPie (ORCPT ); Mon, 13 Jul 2020 11:38:34 -0400 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ADC63C061755; Mon, 13 Jul 2020 08:38:34 -0700 (PDT) Received: by mail-pl1-x641.google.com with SMTP id t6so2505276plo.3; Mon, 13 Jul 2020 08:38:34 -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:user-agent; bh=EkuY5nTWtYjHN6dlAxhuSPoKlCvkK/wdqr04aL31t4o=; b=A+JNrFxppxl73xfHd+hlQqaFZfE2iKKbu7A43CSIk8a5+LopIJtGENZPiCYhgs/gyX /8KkoSDz32K4LCHddQAx34yTodb28lKG6+eZUiVfbCGajqhc7SlLoj/oKtj2b1uzK7Ps 64lGg6lN4nV28DYLPGjA+ZlLA1XTw5qqT1BOShmQxgN9ISQFYWv94rajZkK0eHJKfeVp rCjyCz/ybWcP87gDBjCJ7QfNleYSJrut+ARdSQRILVPJ8N9H2NQ1CVX5YbZq9zQ8Hxy6 I9j/yVUrlyoSUYP4OqqfZI6d08SwFtXXfgskPDEhc8iM53Kkias6nfv/lzUGYiIVQ3to 6+3Q== 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:user-agent; bh=EkuY5nTWtYjHN6dlAxhuSPoKlCvkK/wdqr04aL31t4o=; b=bYFDyrmurceX4efQ2gET3PfomCSeF/dcYT2yuQliavyVqXaHfNp9HJuwxwC5IlKGEU rqpG0XJQ9XVvhsXN8fW5fdYo+HF8eFrPpQLB2Z6FJyJ6BYZIRA5Gvp1fYvXPfsiLCQ68 DF5RK3bb6bUyscruqHy+xRHTYDhWWN0PPV+FjosZ/qWfAGelCARa46lNAHlW5caMK60c RmVPWkCGKMausn1OLl4F+TN6eZDNaxONhWOObcudvtw5bQ4DKa/+GvmYsvxG4sXKQVQ+ tA4dccCc6qFfSCHTGO1c1jf7NRI7yzMyebCNkJBRuXOCMVYhAAcumzSq4hYla2Ig/zvO /3UQ== X-Gm-Message-State: AOAM532aXi4bycbJHXKEjkS750vgZgi5e81+SGyxL5w3JZc8kUIwoLYC 1884BDxr/qkSRdNo/lQIGcY= X-Google-Smtp-Source: ABdhPJy0kUiywZaC/bxx58Daz314s+l4aZe3uztdWBi8TKRWWU3gTwcr1gL27+OzebJ20UptMK4uEw== X-Received: by 2002:a17:902:7484:: with SMTP id h4mr174821pll.243.1594654714276; Mon, 13 Jul 2020 08:38:34 -0700 (PDT) Received: from hoboy (c-73-241-114-122.hsd1.ca.comcast.net. [73.241.114.122]) by smtp.gmail.com with ESMTPSA id q13sm16050804pfk.8.2020.07.13.08.38.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2020 08:38:33 -0700 (PDT) Date: Mon, 13 Jul 2020 08:38:31 -0700 From: Richard Cochran To: Vladimir Oltean Cc: Kurt Kanzenbach , Andrew Lunn , Vivien Didelot , Florian Fainelli , "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org, Rob Herring , devicetree@vger.kernel.org, Sebastian Andrzej Siewior , Kamil Alkhouri , ilias.apalodimas@linaro.org Subject: Re: [PATCH v1 4/8] net: dsa: hellcreek: Add support for hardware timestamping Message-ID: <20200713153831.GA29291@hoboy> References: <20200710113611.3398-1-kurt@linutronix.de> <20200710113611.3398-5-kurt@linutronix.de> <20200713095700.rd4u4t6thkzfnlll@skbuf> <87k0z7n0m9.fsf@kurt> <20200713140112.GB27934@hoboy> <20200713141217.ktgh5rtullmrjjsy@skbuf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200713141217.ktgh5rtullmrjjsy@skbuf> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, Jul 13, 2020 at 05:12:17PM +0300, Vladimir Oltean wrote: > On Mon, Jul 13, 2020 at 07:01:12AM -0700, Richard Cochran wrote: > > I don't think it makes sense for DSA drivers to set this bit, as it > > serves no purpose in the DSA context. > > > > For whom does this bit serve a purpose, though, and how do you tell? It had a historical purpose. Originally, the stack delivered either a hardware or a software time stamp, but not both. This restriction was eventually lifted via the SOF_TIMESTAMPING_OPT_TX_SWHW option, but still the original behavior is preserved as the default. You can see how SKBTX_IN_PROGRESS is used by the skb_tstamp_tx() path here: void __skb_tstamp_tx(struct sk_buff *orig_skb, struct skb_shared_hwtstamps *hwtstamps, struct sock *sk, int tstype) { ... if (!hwtstamps && !(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) && skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS) return; } It prevents SW time stamp when the flag is set. Note that DSA drivers deliver TX time stamps via a different path, namely skb_complete_tx_timestamp(). Also, DSA drivers don't provide SW time stamping at all. Q: When should drivers set SKBTX_IN_PROGRESS? A: When the interface they represent offers both SOF_TIMESTAMPING_TX_HARDWARE and SOF_TIMESTAMPING_TX_SOFTWARE. HTH, Richard