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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=ham 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 28E61C3A5A9 for ; Wed, 4 Sep 2019 21:11:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 004C522CF7 for ; Wed, 4 Sep 2019 21:11:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TH2xF9mp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730956AbfIDVLw (ORCPT ); Wed, 4 Sep 2019 17:11:52 -0400 Received: from mail-pg1-f202.google.com ([209.85.215.202]:44193 "EHLO mail-pg1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730899AbfIDVLv (ORCPT ); Wed, 4 Sep 2019 17:11:51 -0400 Received: by mail-pg1-f202.google.com with SMTP id o21so3579262pgd.11 for ; Wed, 04 Sep 2019 14:11:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=AONGf/XrwQ57qLLsqc1IAcmsTXCE/q6wdhnpClqGQ04=; b=TH2xF9mpWDfyKefZivaec2xL2ZLzp5qmn+OX6MYUIXS2P1CjEvnb+Hi+fFGGne37r+ n5WaCkirA8ys3qam6eq2w/K2LobHixeNannHiGYWMdrhwT5IqXtIrGF/Fq4ThsEtaE0M 6zMs2g088BP5ODUSxygXiKvEVb4ipDr1UDih7zeBZTcrmwVwnUx7v9C87QnD9SzyRexJ lgx7s3bLVkyvLu/ssnM7MB/bNODRixypQRgxHumSL3SpWLpiXre6kSIQ1fy8Cyg4KZSV OzI9XFXbFmzcF+hI9066HuVIAREQztV4usQa43BAXNW5jZmLD7g4BYm0On05mKRRN4JS uJ+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=AONGf/XrwQ57qLLsqc1IAcmsTXCE/q6wdhnpClqGQ04=; b=InpiMUr8rUcg8PaoDQ01LUgxloNmQkMZ9xqQ6v3GBJ8ZNQo+lo5MW4kFV6XFJbydlB upNLzveAUy57qIIUlcyGsSgNHCcq5X4eMleJLIHYUwgywyHpPjbkXolN8sQqMpjM5Q7K VUKaxn0xuDudARyXC1Ln1b7i3Veuw0ePsggll3HoJHX0vEJh/C/3Ozw2dt6Vcw5q7AP6 ZE5QFo7WNzd97GKgGXMaFKa+TS9yfUqfQRXrzgGU/4kP4TDd12k3DY+gTnnvopUb8rNH N7VEKraBWq6umLNkY8uN982eMNzZULvQbGmIjSHXXgQk/XfMFjDbVRdPCZUMmBSYDJpn Eg1g== X-Gm-Message-State: APjAAAWqbMwjqPajD3MJvAWyOCaZuDNLSA6NOZ8dknvQuPacm3hHfNGK LDa7u7sQBI0nuUSfxVCS7Bv35B9EBNENd8U= X-Google-Smtp-Source: APXvYqySn9/+gjnHwwNQKP3hpZKLo+bE+U3qbKQShvLUPwIPN5cMyBzHW3ZdrhgFeLsSv9k5msga7lFRlYMUPrY= X-Received: by 2002:a63:6f8f:: with SMTP id k137mr146678pgc.90.1567631510692; Wed, 04 Sep 2019 14:11:50 -0700 (PDT) Date: Wed, 4 Sep 2019 14:11:25 -0700 In-Reply-To: <20190904211126.47518-1-saravanak@google.com> Message-Id: <20190904211126.47518-7-saravanak@google.com> Mime-Version: 1.0 References: <20190904211126.47518-1-saravanak@google.com> X-Mailer: git-send-email 2.23.0.187.g17f5b7556c-goog Subject: [PATCH v11 6/6] of: property: Create device links for all child-supplier depencencies From: Saravana Kannan To: Rob Herring , Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand , Jonathan Corbet , Len Brown Cc: Saravana Kannan , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-acpi@vger.kernel.org, clang-built-linux@googlegroups.com, David Collins , kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A parent device can have child devices that it adds when it probes. But this probing of the parent device can happen way after kernel init is done -- for example, when the parent device's driver is loaded as a module. In such cases, if the child devices depend on a supplier in the system, we need to make sure the supplier gets the sync_state() callback only after these child devices are added and probed. To achieve this, when creating device links for a device by looking at its DT node, don't just look at DT references at the top node level. Look at DT references in all the descendant nodes too and create device links from the ancestor device to all these supplier devices. This way, when the parent device probes and adds child devices, the child devices can then create their own device links to the suppliers and further delay the supplier's sync_state() callback to after the child devices are probed. Example: In this illustration, -> denotes DT references and indentation represents child status. Device node A Device node B -> D Device node C -> B, D Device node D Assume all these devices have their drivers loaded as modules. Without this patch, this is the sequence of events: 1. D is added. 2. A is added. 3. Device D probes. 4. Device D gets its sync_state() callback. 5. Device B and C might malfunction because their resources got altered/turned off before they can make active requests for them. With this patch, this is the sequence of events: 1. D is added. 2. A is added and creates device links to D. 3. Device link from A to B is not added because A is a parent of B. 4. Device D probes. 5. Device D does not get it's sync_state() callback because consumer A hasn't probed yet. 5. Device A probes. 5. a. Devices B and C are added. 5. b. Device links from B and C to D are added. 5. c. Device A's probe completes. 6. Device D does not get it's sync_state() callback because consumer A has probed but consumers B and C haven't probed yet. 7. Device B and C probe. 8. Device D gets it's sync_state() callback because all its consumers have probed. 9. None of the devices malfunction. Signed-off-by: Saravana Kannan --- drivers/of/property.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/of/property.c b/drivers/of/property.c index 23b5ee5b0570..923d6f88a99c 100644 --- a/drivers/of/property.c +++ b/drivers/of/property.c @@ -1207,6 +1207,10 @@ static int __of_link_to_suppliers(struct device *dev, if (of_link_property(dev, con_np, p->name)) ret = -EAGAIN; + for_each_child_of_node(con_np, child) + if (__of_link_to_suppliers(dev, child)) + ret = -EAGAIN; + return ret; } -- 2.23.0.187.g17f5b7556c-goog