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 5DB6BC433EF for ; Thu, 23 Jun 2022 10:06:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231444AbiFWKGd (ORCPT ); Thu, 23 Jun 2022 06:06:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231233AbiFWKGP (ORCPT ); Thu, 23 Jun 2022 06:06:15 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7AB152AC4E for ; Thu, 23 Jun 2022 03:06:13 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1o4JhK-0001s4-PU; Thu, 23 Jun 2022 12:04:26 +0200 Received: from sha by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1o4JhF-0006Dc-DA; Thu, 23 Jun 2022 12:04:21 +0200 Date: Thu, 23 Jun 2022 12:04:21 +0200 From: sascha hauer To: Saravana Kannan Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Rob Herring , 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: <20220623100421.GY1615@pengutronix.de> References: <20220623080344.783549-1-saravanak@google.com> <20220623080344.783549-3-saravanak@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220623080344.783549-3-saravanak@google.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-Accept-Language: de,en X-Accept-Content-Type: text/plain User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-gpio@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org 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. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |