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 B5040C433EF for ; Mon, 27 Jun 2022 17:50:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238159AbiF0Ruw (ORCPT ); Mon, 27 Jun 2022 13:50:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233113AbiF0Ruv (ORCPT ); Mon, 27 Jun 2022 13:50:51 -0400 Received: from mail-il1-f171.google.com (mail-il1-f171.google.com [209.85.166.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F990767A; Mon, 27 Jun 2022 10:50:50 -0700 (PDT) Received: by mail-il1-f171.google.com with SMTP id a16so6533333ilr.6; Mon, 27 Jun 2022 10:50:50 -0700 (PDT) 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=JMvotdxdopiZeRt2411RNmh3EgUkyNTiH64o+qllFfk=; b=0VT1/m3r2bhQdtpFgOf9s5W4EEhcMapw+0GPLa+Q9mIbcE5Bsq4Fkav7Z2P5B2G7uI hqIzvh8+P8HsgiSRKi5VU2Fb1ggEpY1L0OhtIvEO7aJAxaLGHHV3SVqPMRReI3IH4CRM tP7hbzhM+ySVsruSSGhCWU6TmUaaXZ/S/+OU+CArDGIEHgSApGe6KXDUop3UWJ7HCDxO NI7bOWopt6wVAK48wV7hkrOGZyw6uiY50FRyczxq2nBrNFOyzNooEghEa9fGrOUU81HG jachA6AaqUJ7mpYO2F09/Jr8//Qf0j/I0RZcTsbOox1/almbDHVe5GgdDMk/pXqwVZ2F +N3Q== X-Gm-Message-State: AJIora+JxJCLJ0+ECh0OGEtph3WN1CGgAIke5FFrM43HxK7lmqKXiFTz SygcHEtmouIp5yAi0TURnQ== X-Google-Smtp-Source: AGRyM1vMlh69p3t3S82TZu1a3E/OZD68e6gmsrb96DKcUUIvaZw/486niMVTaLeFL863dLlg1DbVCA== X-Received: by 2002:a92:da4c:0:b0:2d5:4942:151c with SMTP id p12-20020a92da4c000000b002d54942151cmr7774824ilq.54.1656352249605; Mon, 27 Jun 2022 10:50:49 -0700 (PDT) Received: from robh.at.kernel.org ([64.188.179.253]) by smtp.gmail.com with ESMTPSA id f9-20020a02a109000000b00339e3a22dbbsm5056008jag.21.2022.06.27.10.50.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jun 2022 10:50:49 -0700 (PDT) Received: (nullmailer pid 2661321 invoked by uid 1000); Mon, 27 Jun 2022 17:50:46 -0000 Date: Mon, 27 Jun 2022 11:50:46 -0600 From: Rob Herring To: sascha hauer Cc: Saravana Kannan , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand , Andy Shevchenko , Daniel Scally , Heikki Krogerus , Sakari Ailus , Len Brown , peng fan , kevin hilman , ulf hansson , len brown , pavel machek , joerg roedel , will deacon , andrew lunn , heiner kallweit , russell king , "david s. miller" , eric dumazet , jakub kicinski , paolo abeni , linus walleij , hideaki yoshifuji , david ahern , kernel-team@android.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, iommu@lists.linux-foundation.org, netdev@vger.kernel.org, linux-gpio@vger.kernel.org, kernel@pengutronix.de, devicetree@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH v2 2/2] of: base: Avoid console probe delay when fw_devlink.strict=1 Message-ID: <20220627175046.GA2644138-robh@kernel.org> References: <20220623080344.783549-1-saravanak@google.com> <20220623080344.783549-3-saravanak@google.com> <20220623100421.GY1615@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220623100421.GY1615@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, Jun 23, 2022 at 12:04:21PM +0200, sascha hauer wrote: > On Thu, Jun 23, 2022 at 01:03:43AM -0700, Saravana Kannan wrote: > > Commit 71066545b48e ("driver core: Set fw_devlink.strict=1 by default") > > enabled iommus and dmas dependency enforcement by default. On some > > systems, this caused the console device's probe to get delayed until the > > deferred_probe_timeout expires. > > > > We need consoles to work as soon as possible, so mark the console device > > node with FWNODE_FLAG_BEST_EFFORT so that fw_delink knows not to delay > > the probe of the console device for suppliers without drivers. The > > driver can then make the decision on where it can probe without those > > suppliers or defer its probe. > > > > Fixes: 71066545b48e ("driver core: Set fw_devlink.strict=1 by default") > > Reported-by: Sascha Hauer > > Reported-by: Peng Fan > > Signed-off-by: Saravana Kannan > > Tested-by: Peng Fan > > --- > > drivers/of/base.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/of/base.c b/drivers/of/base.c > > index d4f98c8469ed..a19cd0c73644 100644 > > --- a/drivers/of/base.c > > +++ b/drivers/of/base.c > > @@ -1919,6 +1919,8 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align)) > > of_property_read_string(of_aliases, "stdout", &name); > > if (name) > > of_stdout = of_find_node_opts_by_path(name, &of_stdout_options); > > + if (of_stdout) > > + of_stdout->fwnode.flags |= FWNODE_FLAG_BEST_EFFORT; > > The device given in the stdout-path property doesn't necessarily have to > be consistent with the console= parameter. The former is usually > statically set in the device trees contained in the kernel while the > latter is dynamically set by the bootloader. So if you change the > console uart in the bootloader then you'll still run into this trap. > > It's problematic to consult only the device tree for dependencies. I > found several examples of drivers in the tree for which dma support > is optional. They use it if they can, but continue without it when > not available. "hwlock" is another property which consider several > drivers as optional. Also consider SoCs in early upstreaming phases > when the device tree is merged with "dmas" or "hwlock" properties, > but the corresponding drivers are not yet upstreamed. It's not nice > to defer probing of all these devices for a long time. > > I wonder if it wouldn't be a better approach to just probe all devices > and record the device(node) they are waiting on. Then you know that you > don't need to probe them again until the device they are waiting for > is available. Can't we have a driver flag 'I have optional dependencies' that will trigger probe without all dependencies and then the driver can defer probe if required dependencies are not yet met. Rob