From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-13.3 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 045227D913 for ; Thu, 29 Aug 2019 07:46:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727998AbfH2Hq0 (ORCPT ); Thu, 29 Aug 2019 03:46:26 -0400 Received: from mail-pg1-f202.google.com ([209.85.215.202]:39118 "EHLO mail-pg1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727958AbfH2HqZ (ORCPT ); Thu, 29 Aug 2019 03:46:25 -0400 Received: by mail-pg1-f202.google.com with SMTP id t19so1511291pgh.6 for ; Thu, 29 Aug 2019 00:46:25 -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=2WQfeka9QBJ0u6SuW6w6DrBJqjwEt58/QtmjRSQZxGs=; b=Uawm/Ct9U0N5DQ5wL+c4cXY7A15ODdjLSpWbtecf7+bVuGrvVT8yhcn0nHza1nYE22 nlfeGgnpm7skSgEmECryCHA+Qkf+BLESDY0MmQ1S05nkBC2F9qXVejgFxY3hdmY01WFP ZBJHWOt2BU0KO1KxZBdrVp+dViuWjW1grr7wNcw8+PvOHYH6O2NhMtIK8HAfYno4cUxv 3+dL8MMGXmiWrBEzFvEAcBKU5KC9riYNb4/pXhvajgW8wWve63HI3peOzrJepZONSDpj 1LDrxdoOMPTFGJo52Ki1v510UgLOMSrNcm4QS8N0lhbixIwWYCkmw+nLbw3oZ8NAcXXF r14A== 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=2WQfeka9QBJ0u6SuW6w6DrBJqjwEt58/QtmjRSQZxGs=; b=SdmyWX/5PXnLeP4M1Qrt6fGVA3nCOXCo2boQQKlVqHn9f8cAcM1BqQ9v6D/Lr1X7Oz sb4ImskahVgtfqls8cYIHBtiQ6NUiZaxXiVdu3NOshTLxdEvPQ/n9nUnWOw0fgTj09Sl 4OPn34+q7qN7zpUAcgya9Yecsj5btyniFxI4y+ILD6Y3FVqbxeHjiCOwih65emjpUFpL 41yfL8pchIS8yIxtQcEPGTap20eHff4wB5Vs5KgCjHDSl85qeMJVylaKGPCxHZg1mN8N TfzJRhnj4Gou23K7AOxgc/o9W7Rlei3HzHkQkAA+Ou0n7gJVVR3znaXCcnj2KyTasH9+ TCYw== X-Gm-Message-State: APjAAAVLcHmWSEeSJWZN4FNpyxwZr/oALc6V+AHZ0b+cIKWialP6D3cJ B8NwSbHdXJLktOWCBCXEjNqXyuGJ2Yqr7eQ= X-Google-Smtp-Source: APXvYqwZzrFjjrO3w9B/Hx1N3gqqdyIyM5Foq9bn18J8PpxtA1ZufCbOQOb/BhQ1ntceTWa9Kc3liGPAH+ydJyM= X-Received: by 2002:a65:52c5:: with SMTP id z5mr7120687pgp.118.1567064784480; Thu, 29 Aug 2019 00:46:24 -0700 (PDT) Date: Thu, 29 Aug 2019 00:46:01 -0700 In-Reply-To: <20190829074603.70424-1-saravanak@google.com> Message-Id: <20190829074603.70424-6-saravanak@google.com> Mime-Version: 1.0 References: <20190829074603.70424-1-saravanak@google.com> X-Mailer: git-send-email 2.23.0.187.g17f5b7556c-goog Subject: [PATCH v10 5/7] 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-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@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 82052172f508..420c2d428184 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