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=-2.1 required=3.0 tests=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 C10E6C3A5A1 for ; Thu, 22 Aug 2019 16:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96C2E233FD for ; Thu, 22 Aug 2019 16:05:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="E9FNR7ft" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389708AbfHVQFY (ORCPT ); Thu, 22 Aug 2019 12:05:24 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:32817 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729718AbfHVQFY (ORCPT ); Thu, 22 Aug 2019 12:05:24 -0400 Received: by mail-pl1-f194.google.com with SMTP id go14so3722590plb.0; Thu, 22 Aug 2019 09:05:24 -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=NxmU91a+hygMveLYANWk4CJyZEkVhJGaWcBlnfdPFlA=; b=E9FNR7ftdt48+rCHz2opRWv8qkIJf0+Vao826g86k2XiP+kn2Fy9XzsJiMpyJI9uCF Ei3933nhNZl28VIqAp+cp6pVxETs+KERIONH9TsPu7JpYdAyHzZbd+5Xl0t3DhNUpmkY 2/CEV2lQmMkbzZT7TQd8dEBcJi3zKIl2niW2+rrO1zVsABvJwRX7ceMs5SV+C3P4rmXu FGyDUbxNesXsQpSfbtq0gGqwBKKWcgJtu9VwNDcS5Ct1wtWNZNXwMOJp+HJsm8gfDa5V E7Edyo4lYTDzmwkyhTCFfb5i9c/7lVPg2lbOKdnS6XPcWcJx5cgl40yzScd/EapRXCC0 XhXQ== 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=NxmU91a+hygMveLYANWk4CJyZEkVhJGaWcBlnfdPFlA=; b=uZLwREPgA6vQKmoa3/Y7sFd0H8YTQ7GJuDVUoovs6MxFgz5h/uWK461kmpZyKmPM5U 2tswS63M9JBeip9+ovj/c5umNLAf3rbeEsMxEBOdV+rzggdZRAESyzaA4xfslpNMhCrY YYs4z40cE5P/yQBQ1ehpR5SNkm+NwXxaJs3uQrDI92DwpX4WVDjfx9uI4mhLoW+aAmUb CtzjOW1pGLREM/RQv7Sj13mMQz67GDmnPx6WQd7XJeQdt0tOs8dt4mLnFAB0F6b4aln/ nxAFyFp6dHaSnTXuBXFsmrhVCjb58HkFVA/6FgXjI1rts4T/GrGKO8uG16EciK/hsSiP m08Q== X-Gm-Message-State: APjAAAVYUQI9eNJupnKTVW8dPqQpZAhlzOjy4JGCevDQUr6ZQa/RgNvV veitzCxmzR5Q4JR1TiQ39x4= X-Google-Smtp-Source: APXvYqzAdayaj4WD9jYfYK8Ekn2rQK4/yQpFcKRi5Q/V4yUHLo/Vyolh7Tm1O3MifUAat1R4wWUfHA== X-Received: by 2002:a17:902:543:: with SMTP id 61mr40245692plf.20.1566489924071; Thu, 22 Aug 2019 09:05:24 -0700 (PDT) Received: from localhost (c-73-222-71-142.hsd1.ca.comcast.net. [73.222.71.142]) by smtp.gmail.com with ESMTPSA id y188sm27501000pfy.57.2019.08.22.09.05.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Aug 2019 09:05:23 -0700 (PDT) Date: Thu, 22 Aug 2019 09:05:21 -0700 From: Richard Cochran To: Vladimir Oltean Cc: Mark Brown , Hubert Feurstein , Miroslav Lichvar , Andrew Lunn , Florian Fainelli , linux-spi@vger.kernel.org, netdev Subject: Re: [PATCH spi for-5.4 0/5] Deterministic SPI latency with NXP DSPI driver Message-ID: <20190822160521.GC4522@localhost> References: <20190818182600.3047-1-olteanv@gmail.com> <20190821043845.GB1332@localhost> <20190821140815.GA1447@localhost> <20190822141641.GB1437@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) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Aug 22, 2019 at 05:58:49PM +0300, Vladimir Oltean wrote: > I don't think I understand the problem here. On the contrary, I do. > You'd have something like this: > > Master (DSA master port) Slave (switch CPU port) > > | | Tstamps known > | | to slave > | Local_sync_req | > t1 |------\ | t1 > | \-----\ | > | \-----\ | > | \----->| t2 t1, t2 > | | > | Local_sync_resp /------| t3 t1, t2, t3 > | /-----/ | > | /-----/ | > t4 |<-----/ | t1, t2, t3, t4 > | | > | | > v time v And who generates Local_sync_resp? Also, what sort of frame is it? PTP has no Sync request or response. > But you don't mean a TX timestamp at the egress of swp4 here, do you? Yes, I do. > Why would that matter? Because in order to synchronize to an external GM, you need to measure two things: 1. the (unchanging) delay from MAC to MAC 2. the (per-packet) switch residence time Thanks, Richard