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=-5.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 D1766C54FCC for ; Mon, 20 Apr 2020 09:36:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B07B220A8B for ; Mon, 20 Apr 2020 09:36:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=daemons-net.20150623.gappssmtp.com header.i=@daemons-net.20150623.gappssmtp.com header.b="zBk0M5IV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726200AbgDTJgW (ORCPT ); Mon, 20 Apr 2020 05:36:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726307AbgDTJgU (ORCPT ); Mon, 20 Apr 2020 05:36:20 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1DB9BC061A0F for ; Mon, 20 Apr 2020 02:36:20 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id a7so3970958pju.2 for ; Mon, 20 Apr 2020 02:36:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=daemons-net.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=3DGhAD7IJSYwN5Mh5wLkFIUQWPuH8Xyr5nhCfZdhrRE=; b=zBk0M5IVJTUHZhgTJvFVpuI50jKguU5uoGrX54baKAYHE3pFHiaWlt+kDCmF45FGY9 J/qX6D+oHD+PEzRPiyyGOdn/sMaFkKT9QBk5NCK1xWLKcyQakpCQQtO8/2jrEXGU9t4V +srfyBTS/ERMCJSmCejLk0o/fWlPGPo0BXoUmxHqshzGIDuNT1PL6za/0tvgI/GltBWg +QjypSIht2By96xTrQ4Lifzuei9gj/dac64sJgtL/Gzyorq4BJUubtILITWTp+8Uo7Iv 3lNXNiGJgIVg0JBWnfqJE3spIiCVVZ3YrQ7hNF1dXnp3SF34CzfbpsDcEPXuSKBCEpAA WLCQ== 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:content-transfer-encoding :in-reply-to:user-agent; bh=3DGhAD7IJSYwN5Mh5wLkFIUQWPuH8Xyr5nhCfZdhrRE=; b=o6eBeMmh/blNquedKXsnesaacbP7Xo7dvYbgXwpZQHatoYgQI+chLEMRmJM2VUyjga MkNd3AcVesSvX7VLbpUwTctbd4rYrpoxFSpLG2/3b88QCQ7BeWxBzQ0BhvtzLzXKpQaD iOWyyfkAZJzrwIDE70X61WRc/W0lE8pZGtO6FjC8DF0NXP7s46idC+78eJR4U/emEPaV uWara+NWzRGO2wklRtRV1xjOcweqDfqH7HGGPI8dvZ6E/CdEE9hcACcL3e6iliwYwbY1 XDFUEhG5WgJx5y2h77glZukWYGFY4hvJ8jo7rQ+7hmJUC/rP3IgzC6MSypclotHz+YfS 7loA== X-Gm-Message-State: AGi0Pua1SMBHLdZ+w9eYrnCv9eN1K5E2NYelw3cA5EYbhicADyFpnUqN vRNTakt4j51f0wA6i66Rfo7z X-Google-Smtp-Source: APiQypIFyoGdo5N2UATcTDeToHVhHOExE0hyeqDVi9r+wjICYlrbxxJlpXV9YK979M9CMtO6YnDT+Q== X-Received: by 2002:a17:902:b101:: with SMTP id q1mr15411011plr.246.1587375379433; Mon, 20 Apr 2020 02:36:19 -0700 (PDT) Received: from arctic-shiba-lx ([47.156.151.166]) by smtp.gmail.com with ESMTPSA id u21sm677223pga.21.2020.04.20.02.36.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2020 02:36:18 -0700 (PDT) Date: Mon, 20 Apr 2020 02:36:10 -0700 From: Clay McClure To: Grygorii Strashko Cc: "David S. Miller" , Sekhar Nori , Richard Cochran , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: cpts: Condition WARN_ON on PTP_1588_CLOCK Message-ID: <20200420093610.GA28162@arctic-shiba-lx> References: <20200416085627.1882-1-clay@daemons.net> <6fef3a00-6c18-b775-d1b4-dfd692261bd3@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6fef3a00-6c18-b775-d1b4-dfd692261bd3@ti.com> 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, Apr 16, 2020 at 02:11:45PM +0300, Grygorii Strashko wrote: Grygorii, > > CPTS_MOD merely implies PTP_1588_CLOCK; it is possible to build cpts > > without PTP clock support. In that case, ptp_clock_register() returns > > NULL and we should not WARN_ON(cpts->clock) when downing the interface. > > The ptp_*() functions are stubbed without PTP_1588_CLOCK, so it's safe > > to pass them a null pointer. > > Could you explain the purpose of the exercise (Enabling CPTS with > PTP_1588_CLOCK disabled), pls? Hardware timestamping with a free-running PHC _almost_ works without PTP_1588_CLOCK, but since PHC rollover is handled by the PTP kworker in this driver the timestamps end up not being monotonic. And of course the moment you want to syntonize/synchronize the PHC with another clock (say, CLOCK_REALTIME), you'll need a PTP clock device. So you're right, there's not much point in building CPTS_MOD without PTP_1588_CLOCK. Given that, I wonder why all the Ethernet drivers seem to just `imply` PTP_1588_CLOCK, rather than `depends on` it? In any case, I was surprised to get a warning during `ifdown` but not during `ifup`. What do you think of this change, which prints an error like this during `ifup` if PTP_1588_CLOCK is not enabled: [ 6.192707] 000: cpsw 4a100000.ethernet: error registering cpts device --- diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c index 10ad706dda53..70b15039cd37 100644 --- a/drivers/net/ethernet/ti/cpts.c +++ b/drivers/net/ethernet/ti/cpts.c @@ -462,8 +462,8 @@ int cpts_register(struct cpts *cpts) timecounter_init(&cpts->tc, &cpts->cc, ktime_get_real_ns()); cpts->clock = ptp_clock_register(&cpts->info, cpts->dev); - if (IS_ERR(cpts->clock)) { - err = PTR_ERR(cpts->clock); + if (IS_ERR_OR_NULL(cpts->clock)) { + err = cpts->clock ? PTR_ERR(cpts->clock) : -EOPNOTSUPP; cpts->clock = NULL; goto err_ptp; } --  Clay