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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 3E048C7618B for ; Thu, 25 Jul 2019 13:42:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 175AD2238C for ; Thu, 25 Jul 2019 13:42:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564062141; bh=WXWR1Y2i0YG6mr1nhE0Yc2dl5l/bxd4nTtbBmCEm9l8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Jvqgqn5Gp0NAxorKkDJYQFW3kY7eE0JCKAgg0+gcoHJV9sZzzhUo9BbISqz7b4YMB Qx91gvOVf83eaKA9nQe3nLiCfzTcDCXrRxvdCYuK+e1Lvog419F98EXDlox+/mWSFG CuXtCT88aBYhUEaciWXR2pXWLJm6bUbSWvbVqw+Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390096AbfGYNmU (ORCPT ); Thu, 25 Jul 2019 09:42:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:48270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389989AbfGYNmS (ORCPT ); Thu, 25 Jul 2019 09:42:18 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 99BE72238C; Thu, 25 Jul 2019 13:42:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564062137; bh=WXWR1Y2i0YG6mr1nhE0Yc2dl5l/bxd4nTtbBmCEm9l8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=euxSMtDuQF2FfuclgA4knYbYqjBAlCbqIJsi9m8N+oopRWZEJFBmcNtEQE9gweuI1 NjGod3ir2lY+CRrgaZXr0LhZzdrnmuhu11GS+zqBl5LgC1YZ1J0W/PQTVjpkphmzpH 0r93wEiZw7xrPO5qoCgxebVErHNBerWWmtMMDWEE= Date: Thu, 25 Jul 2019 15:42:14 +0200 From: Greg Kroah-Hartman To: Saravana Kannan Cc: Rob Herring , Mark Rutland , "Rafael J. Wysocki" , Frank Rowand , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, David Collins , kernel-team@android.com Subject: Re: [PATCH v7 0/7] Solve postboot supplier cleanup and optimize probe ordering Message-ID: <20190725134214.GD11115@kroah.com> References: <20190724001100.133423-1-saravanak@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190724001100.133423-1-saravanak@google.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 23, 2019 at 05:10:53PM -0700, Saravana Kannan wrote: > Add device-links to track functional dependencies between devices > after they are created (but before they are probed) by looking at > their common DT bindings like clocks, interconnects, etc. > > Having functional dependencies automatically added before the devices > are probed, provides the following benefits: > > - Optimizes device probe order and avoids the useless work of > attempting probes of devices that will not probe successfully > (because their suppliers aren't present or haven't probed yet). > > For example, in a commonly available mobile SoC, registering just > one consumer device's driver at an initcall level earlier than the > supplier device's driver causes 11 failed probe attempts before the > consumer device probes successfully. This was with a kernel with all > the drivers statically compiled in. This problem gets a lot worse if > all the drivers are loaded as modules without direct symbol > dependencies. > > - Supplier devices like clock providers, interconnect providers, etc > need to keep the resources they provide active and at a particular > state(s) during boot up even if their current set of consumers don't > request the resource to be active. This is because the rest of the > consumers might not have probed yet and turning off the resource > before all the consumers have probed could lead to a hang or > undesired user experience. > > Some frameworks (Eg: regulator) handle this today by turning off > "unused" resources at late_initcall_sync and hoping all the devices > have probed by then. This is not a valid assumption for systems with > loadable modules. Other frameworks (Eg: clock) just don't handle > this due to the lack of a clear signal for when they can turn off > resources. This leads to downstream hacks to handle cases like this > that can easily be solved in the upstream kernel. > > By linking devices before they are probed, we give suppliers a clear > count of the number of dependent consumers. Once all of the > consumers are active, the suppliers can turn off the unused > resources without making assumptions about the number of consumers. > > By default we just add device-links to track "driver presence" (probe > succeeded) of the supplier device. If any other functionality provided > by device-links are needed, it is left to the consumer/supplier > devices to change the link when they probe. > > v1 -> v2: > - Drop patch to speed up of_find_device_by_node() > - Drop depends-on property and use existing bindings > > v2 -> v3: > - Refactor the code to have driver core initiate the linking of devs > - Have driver core link consumers to supplier before it's probed > - Add support for drivers to edit the device links before probing > > v3 -> v4: > - Tested edit_links() on system with cyclic dependency. Works. > - Added some checks to make sure device link isn't attempted from > parent device node to child device node. > - Added way to pause/resume sync_state callbacks across > of_platform_populate(). > - Recursively parse DT node to create device links from parent to > suppliers of parent and all child nodes. > > v4 -> v5: > - Fixed copy-pasta bugs with linked list handling > - Walk up the phandle reference till I find an actual device (needed > for regulators to work) > - Added support for linking devices from regulator DT bindings > - Tested the whole series again to make sure cyclic dependencies are > broken with edit_links() and regulator links are created properly. > > v5 -> v6: > - Split, squashed and reordered some of the patches. > - Refactored the device linking code to follow the same code pattern for > any property. > > v6 -> v7: > - No functional changes. > - Renamed i to index > - Added comment to clarify not having to check property name for every > index > - Added "matched" variable to clarify code. No functional change. > - Added comments to include/linux/device.h for add_links() > > I've also not updated this patch series to handle the new patch [1] from > Rafael. Will do that once this patch series is close to being Acked. > > [1] - https://lore.kernel.org/lkml/3121545.4lOhFoIcdQ@kreacher/ This looks sane to me. Anyone have any objections for me queueing this up for my tree to get into linux-next now? thanks, greg k-h