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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 333DBC4332B for ; Wed, 27 Jan 2021 15:35:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09B7D207E2 for ; Wed, 27 Jan 2021 15:35:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235509AbhA0PfT (ORCPT ); Wed, 27 Jan 2021 10:35:19 -0500 Received: from mail.kernel.org ([198.145.29.99]:56844 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235196AbhA0PFO (ORCPT ); Wed, 27 Jan 2021 10:05:14 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2C359207D8; Wed, 27 Jan 2021 15:04:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1611759873; bh=A5lQceW5WkUV3NZnaUs4+oJ/FTWq97QkH8sVu2gmDxI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GGdWepzCfbLCO2phk+j0D0bqMvwv8XEWgT2bYxwztDmIgxFnXa/wgjb9EuyrIh2YD 1uTfhT/K8AHZPl4ITw1qqumb0eKJiTUByjBWrp8GGHTKK6O3p6EMhVZP5GQHs1wANx cxxaY0iR+6fwiInu54C+PFqHe834IWZ5hQUY9cic= Date: Wed, 27 Jan 2021 16:04:30 +0100 From: Greg Kroah-Hartman To: Bartosz Golaszewski Cc: Saravana Kannan , Linus Walleij , Marc Zyngier , Jisheng Zhang , Kever Yang , kernel-team@android.com, linux-gpio , LKML Subject: Re: [PATCH v5] gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default Message-ID: References: <20210122193600.1415639-1-saravanak@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 27, 2021 at 03:31:17PM +0100, Bartosz Golaszewski wrote: > On Wed, Jan 27, 2021 at 3:22 PM Greg Kroah-Hartman > wrote: > > > > On Fri, Jan 22, 2021 at 11:35:59AM -0800, Saravana Kannan wrote: > > > There are multiple instances of GPIO device tree nodes of the form: > > > > > > foo { > > > compatible = "acme,foo"; > > > ... > > > > > > gpio0: gpio0@xxxxxxxx { > > > compatible = "acme,bar"; > > > ... > > > gpio-controller; > > > }; > > > > > > gpio1: gpio1@xxxxxxxx { > > > compatible = "acme,bar"; > > > ... > > > gpio-controller; > > > }; > > > > > > ... > > > } > > > > > > bazz { > > > my-gpios = <&gpio0 ...>; > > > } > > > > > > Case 1: The driver for "foo" populates struct device for these gpio* > > > nodes and then probes them using a driver that binds with "acme,bar". > > > This driver for "acme,bar" then registers the gpio* nodes with gpiolib. > > > This lines up with how DT nodes with the "compatible" property are > > > typically converted to struct devices and then registered with driver > > > core to probe them. This also allows the gpio* devices to hook into all > > > the driver core capabilities like runtime PM, probe deferral, > > > suspend/resume ordering, device links, etc. > > > > > > Case 2: The driver for "foo" doesn't populate struct devices for these > > > gpio* nodes before registering them with gpiolib. Instead it just loops > > > through its child nodes and directly registers the gpio* nodes with > > > gpiolib. > > > > > > Drivers that follow case 2 cause problems with fw_devlink=on. This is > > > because fw_devlink will prevent bazz from probing until there's a struct > > > device that has gpio0 as its fwnode (because bazz lists gpio0 as a GPIO > > > supplier). Once the struct device is available, fw_devlink will create a > > > device link with gpio0 device as the supplier and bazz device as the > > > consumer. After this point, since the gpio0 device will never bind to a > > > driver, the device link will prevent bazz device from ever probing. > > > > > > Finding and refactoring all the instances of drivers that follow case 2 > > > will cause a lot of code churn and it is not something that can be done > > > in one shot. In some instances it might not even be possible to refactor > > > them cleanly. Examples of such instances are [1] [2]. > > > > > > This patch works around this problem and avoids all the code churn by > > > simply setting the fwnode of the gpio_device and creating a stub driver > > > to bind to the gpio_device. This allows all the consumers to continue > > > probing when the driver follows case 2. > > > > > > [1] - https://lore.kernel.org/lkml/20201014191235.7f71fcb4@xhacker.debian/ > > > [2] - https://lore.kernel.org/lkml/e28e1f38d87c12a3c714a6573beba6e1@kernel.org/ > > > Cc: Marc Zyngier > > > Cc: Jisheng Zhang > > > Cc: Kever Yang > > > Fixes: e590474768f1 ("driver core: Set fw_devlink=on by default") > > > > As this commit is in my driver-core git tree, can I just take this in > > the same tree? Can I get an ack from the maintainer for this? > > > > thanks, > > > > greg k-h > > Go ahead. > > Acked-by: Bartosz Golaszewski Thanks, now queued up. greg k-h