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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 2FF0EC433E9 for ; Thu, 21 Jan 2021 22:39:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE7F723A7E for ; Thu, 21 Jan 2021 22:39:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726963AbhAUWis (ORCPT ); Thu, 21 Jan 2021 17:38:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726643AbhAUWik (ORCPT ); Thu, 21 Jan 2021 17:38:40 -0500 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 602CFC061756 for ; Thu, 21 Jan 2021 14:38:00 -0800 (PST) Received: by mail-pf1-x44a.google.com with SMTP id x206so2089543pfc.16 for ; Thu, 21 Jan 2021 14:38:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=MopP3ly3bA3eMHB1Y9//RmGNL7s+QTEOsJtmIObREmY=; b=MEtgBsAiJAWzjTXNj0Kyb544HT8CFWU9eqOGurRGiEnWlDib4RRvUzwNUpT5xyJMZG /C04/VuRPk7kbkXh2lGXpvGLu/jHTg3lp21DW0FXtQof0mygH0q+0bFYVt8In5Yn0t2X eyPOntSR6JJqdRdUH+QTA05LDLmd+9I0o3gouyn0HIlzsH0YKNSj1NkMmX44/e4x7unI Mvnm0uH6I7uKXJVbCmO/gp2gTxCUjtXZQEY/mVwDKYsVuQ4b5TiTa6aF3DAs/Y9EB0YD rd91Oi0WLzVFvxOI/ejfqIQSh5iuwyNtBUK/lqJNXvGb7tZNVn6KlwGnXPb6j2r7gve+ 6HpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=MopP3ly3bA3eMHB1Y9//RmGNL7s+QTEOsJtmIObREmY=; b=c+YYONb0nXHKzskGWecNZ8cJ8JYLGvwipQ3vTLtm1EcTevS8A57555lopjhP4VZjDw Mg3CsAHP1oYHTAU2fRCsHOLZ99ZtrYzIh2bZGHAfKNK9Kyk7lIL6bYQ+Tj2BYk9d6vpE 6CGy0yPvPgYr9iiAPZGBytbEsJfCU0wRxM7dTMfL/1CyOrLVzv1ZH9JfYMN0XUE7yaE9 knHZHOImyLj8MP8QoKm08tzIIKNiOlxWmR2K5AKAsxwYG5IaAMFBiFn2OblnFNw/PU0g E/KpQ4EQ1UF4whTneHq2/Y2DiovpwfVq13NK9hYxzmz/v8wyDNccmRbmI0lCO0qi9NUJ heBA== X-Gm-Message-State: AOAM530PcgV4AO6scMb+6dQHiQ9djWN0UuTogRcBegyyxqeCuOmKD3dK pD0VHCPZ9GQE5HawUegDpiP/hDCMRWQE2nc= X-Google-Smtp-Source: ABdhPJz0NkBI32v4RrdI7Lh0LHnl+nzLY849ZAp3v7+PfBG67Wykw/8zcPqdJE2zPV8PIZ7jfC0kcjWcEJFCOko= Sender: "saravanak via sendgmr" X-Received: from saravanak.san.corp.google.com ([2620:15c:2d:3:7220:84ff:fe09:fedc]) (user=saravanak job=sendgmr) by 2002:a63:720c:: with SMTP id n12mr1529729pgc.97.1611268679599; Thu, 21 Jan 2021 14:37:59 -0800 (PST) Date: Thu, 21 Jan 2021 14:37:56 -0800 Message-Id: <20210121223756.1112199-1-saravanak@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.30.0.280.ga3ce27912f-goog Subject: [PATCH v4] gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default From: Saravana Kannan To: Linus Walleij , Bartosz Golaszewski , Saravana Kannan , Greg Kroah-Hartman Cc: Marc Zyngier , Jisheng Zhang , Kever Yang , kernel-team@android.com, linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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") Signed-off-by: Saravana Kannan --- v1 -> v2: - Fixed up compilation errors that were introduced accidentally - Fixed a missing put_device() v2 -> v3: - Changed chip_warn() to pr_warn() - Changed some variable names v3 -> v4: - Dropped the warning since it's not always valid - This simplifies the code a lot - Added comments and fixed up commit text drivers/gpio/gpiolib.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index b02cc2abd3b6..f42eaca08d9a 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -596,6 +596,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, gdev->dev.of_node = gc->of_node; else gc->of_node = gdev->dev.of_node; + gdev->dev.fwnode = of_fwnode_handle(gdev->dev.of_node); #endif gdev->id = ida_alloc(&gpio_ida, GFP_KERNEL); @@ -4202,6 +4203,29 @@ void gpiod_put_array(struct gpio_descs *descs) } EXPORT_SYMBOL_GPL(gpiod_put_array); +static int gpio_stub_drv_probe(struct device *dev) +{ + /* + * The DT node of some GPIO chips have a "compatible" property, but + * never have a struct device added and probed by a driver to register + * the GPIO chip with gpiolib. In such cases, fw_devlink=on will cause + * the consumers of the GPIO chip to get probe deferred forever because + * they will be waiting for a device associated with the GPIO chip + * firmware node to get added and bound to a driver. + * + * To allow these consumers to probe, we associate the struct + * gpio_device of the GPIO chip with the firmware node and then simply + * bind it to this stub driver. + */ + return 0; +} + +static struct device_driver gpio_stub_drv = { + .name = "gpio_stub_drv", + .bus = &gpio_bus_type, + .probe = gpio_stub_drv_probe, +}; + static int __init gpiolib_dev_init(void) { int ret; @@ -4213,9 +4237,16 @@ static int __init gpiolib_dev_init(void) return ret; } + if (driver_register(&gpio_stub_drv) < 0) { + pr_err("gpiolib: could not register GPIO stub driver\n"); + bus_unregister(&gpio_bus_type); + return ret; + } + ret = alloc_chrdev_region(&gpio_devt, 0, GPIO_DEV_MAX, GPIOCHIP_NAME); if (ret < 0) { pr_err("gpiolib: failed to allocate char dev region\n"); + driver_unregister(&gpio_stub_drv); bus_unregister(&gpio_bus_type); return ret; } -- 2.30.0.280.ga3ce27912f-goog