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 74769C76197 for ; Sat, 20 Jul 2019 06:17:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D64821872 for ; Sat, 20 Jul 2019 06:17:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="jhWeaEAs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726358AbfGTGRG (ORCPT ); Sat, 20 Jul 2019 02:17:06 -0400 Received: from mail-qt1-f201.google.com ([209.85.160.201]:38425 "EHLO mail-qt1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726328AbfGTGRF (ORCPT ); Sat, 20 Jul 2019 02:17:05 -0400 Received: by mail-qt1-f201.google.com with SMTP id r58so29849767qtb.5 for ; Fri, 19 Jul 2019 23:17:05 -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=Og1mQTkoBXXuVmW9REcEW86ek8LbY7FIolyGM3Z5bgQ=; b=jhWeaEAsKTy4JC/sfjf9cTu2h5M+N+o9Q4FfTdmeNdB7KuyHSjFIuO1dItmHeV5mvp Xn7+Bzn7LSPL2qVoBHW5cvdvwtH7FB60bcwoxFwaSZ+Ff/dSrExgxbdDRtix7xqa9cBt eBd1jcRu9t185Cb80k09pATa5RJ3KFaCRZCAXasQKW5yIWpMEaZt7HFhqrEe6amTvTrI wmApWHPoqbAeDchGdb3VC9GhRpuAmznNP4ps5x1OQfXuWZ9pZhLWMyFfysGz4SfoSPmw nq5LlyjXY89bjX8kaH7NC8BRyGfKEu474thyR4ijoNVyysktQHIYToQoFLPKw5FXK+0I wYLg== 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=Og1mQTkoBXXuVmW9REcEW86ek8LbY7FIolyGM3Z5bgQ=; b=cV/WqfPgc6dJkMalibyRZoPbkPgOqj4tkbAlTDMet3hi6OLqpFWVONRVHu/zCkBEPw 2QYVfccuhQccXQOrts5zBBHk9SPgpr0N+z7SAKY0uqvkCCuMcvfngfsZ0yAtTQMfVUT+ PMIb2AcaYepf3zvxGKYD7giaaoBSgv+dNNcqGr9GvkGMzulw7dRkk8rZtK17p4qKiHGh QFWjDM33UV1+n7/n1ORozOKfw6ShG6MakP2qrvMApybpGB4ODvDUaH1zpuJprExPMQNS 7We1LXIOLwG4HwSldsiX5UNKS9joSzWKV1cOzbaw+gNRVYI46zvL5SNXG/oZfL26ta1U LM4A== X-Gm-Message-State: APjAAAWS1ULZvqN2Ra+gJgOEddvC0tWHprB9KOOQ8BKv0XvIdl6yqQK4 FUBy9pbTPvqjCpSeATyS8mGm9DwdKX9FnZw= X-Google-Smtp-Source: APXvYqz0mSnepFmFR82ABoetJqAuNQphWIzPe508tQEck+N6DfNGK0n2KiJkoQN9nf5Ic3tzE07AK6NnVWfBlCE= X-Received: by 2002:ac8:333d:: with SMTP id t58mr41352177qta.167.1563603424389; Fri, 19 Jul 2019 23:17:04 -0700 (PDT) Date: Fri, 19 Jul 2019 23:16:42 -0700 In-Reply-To: <20190720061647.234852-1-saravanak@google.com> Message-Id: <20190720061647.234852-4-saravanak@google.com> Mime-Version: 1.0 References: <20190720061647.234852-1-saravanak@google.com> X-Mailer: git-send-email 2.22.0.657.g960e92d24f-goog Subject: [PATCH v6 3/7] of/platform: Add functional dependency link from DT bindings From: Saravana Kannan To: Rob Herring , Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand , Jonathan Corbet Cc: Saravana Kannan , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, David Collins , kernel-team@android.com, linux-doc@vger.kernel.org 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 Add device-links after the devices are created (but before they are probed) by looking at common DT bindings like clocks and interconnects. Automatically adding device-links for functional dependencies at the framework level 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. Signed-off-by: Saravana Kannan --- .../admin-guide/kernel-parameters.txt | 5 + drivers/of/platform.c | 158 ++++++++++++++++++ 2 files changed, 163 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 138f6664b2e2..109b4310844f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3141,6 +3141,11 @@ This can be set from sysctl after boot. See Documentation/sysctl/vm.txt for details. + of_devlink [KNL] Make device links from common DT bindings. Useful + for optimizing probe order and making sure resources + aren't turned off before the consumer devices have + probed. + ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. See Documentation/debugging-via-ohci1394.txt for more info. diff --git a/drivers/of/platform.c b/drivers/of/platform.c index 04ad312fd85b..88a2086e26fa 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c @@ -509,6 +509,163 @@ int of_platform_default_populate(struct device_node *root, } EXPORT_SYMBOL_GPL(of_platform_default_populate); +bool of_link_is_valid(struct device_node *con, struct device_node *sup) +{ + of_node_get(sup); + /* + * Don't allow linking a device node as a consumer of one of its + * descendant nodes. By definition, a child node can't be a functional + * dependency for the parent node. + */ + while (sup) { + if (sup == con) { + of_node_put(sup); + return false; + } + sup = of_get_next_parent(sup); + } + return true; +} + +static int of_link_to_phandle(struct device *dev, struct device_node *sup_np) +{ + struct platform_device *sup_dev; + u32 dl_flags = DL_FLAG_AUTOPROBE_CONSUMER; + int ret = 0; + + /* + * Since we are trying to create device links, we need to find + * the actual device node that owns this supplier phandle. + * Often times it's the same node, but sometimes it can be one + * of the parents. So walk up the parent till you find a + * device. + */ + while (sup_np && !of_find_property(sup_np, "compatible", NULL)) + sup_np = of_get_next_parent(sup_np); + if (!sup_np) + return 0; + + if (!of_link_is_valid(dev->of_node, sup_np)) { + of_node_put(sup_np); + return 0; + } + sup_dev = of_find_device_by_node(sup_np); + of_node_put(sup_np); + if (!sup_dev) + return -ENODEV; + if (!device_link_add(dev, &sup_dev->dev, dl_flags)) + ret = -ENODEV; + put_device(&sup_dev->dev); + return ret; +} + +static struct device_node *parse_prop_cells(struct device_node *np, + const char *prop, int i, + const char *binding, + const char *cell) +{ + struct of_phandle_args sup_args; + + if (!i && strcmp(prop, binding)) + return NULL; + + if (of_parse_phandle_with_args(np, binding, cell, i, &sup_args)) + return NULL; + + return sup_args.np; +} + +static struct device_node *parse_clocks(struct device_node *np, + const char *prop, int i) +{ + return parse_prop_cells(np, prop, i, "clocks", "#clock-cells"); +} + +static struct device_node *parse_interconnects(struct device_node *np, + const char *prop, int i) +{ + return parse_prop_cells(np, prop, i, "interconnects", + "#interconnect-cells"); +} + +static int strcmp_suffix(const char *str, const char *suffix) +{ + unsigned int len, suffix_len; + + len = strlen(str); + suffix_len = strlen(suffix); + if (len <= suffix_len) + return -1; + return strcmp(str + len - suffix_len, suffix); +} + +static struct device_node *parse_regulators(struct device_node *np, + const char *prop, int i) +{ + if (i || strcmp_suffix(prop, "-supply")) + return NULL; + + return of_parse_phandle(np, prop, 0); +} + +/** + * struct supplier_bindings - Information for parsing supplier DT binding + * + * @parse_prop: If the function cannot parse the property, return NULL. + * Otherwise, return the phandle listed in the property + * that corresponds to index i. + */ +struct supplier_bindings { + struct device_node *(*parse_prop)(struct device_node *np, + const char *name, int i); +}; + +struct supplier_bindings bindings[] = { + { .parse_prop = parse_clocks, }, + { .parse_prop = parse_interconnects, }, + { .parse_prop = parse_regulators, }, + { }, +}; + +static bool of_link_property(struct device *dev, struct device_node *con_np, + const char *prop) +{ + struct device_node *phandle; + struct supplier_bindings *s = bindings; + unsigned int i = 0; + bool done = true; + + while (!i && s->parse_prop) { + while ((phandle = s->parse_prop(con_np, prop, i))) { + i++; + if (of_link_to_phandle(dev, phandle)) + done = false; + } + s++; + } + return done ? 0 : -ENODEV; +} + +static bool of_devlink; +core_param(of_devlink, of_devlink, bool, 0); + +static int of_link_to_suppliers(struct device *dev) +{ + struct property *p; + bool done = true; + + if (!of_devlink) + return 0; + if (unlikely(!dev->of_node)) + return 0; + + for_each_property_of_node(dev->of_node, p) + if (of_link_property(dev, dev->of_node, p->name)) + done = false; + + return done ? 0 : -ENODEV; +} + #ifndef CONFIG_PPC static const struct of_device_id reserved_mem_matches[] = { { .compatible = "qcom,rmtfs-mem" }, @@ -524,6 +681,7 @@ static int __init of_platform_default_populate_init(void) if (!of_have_populated_dt()) return -ENODEV; + platform_bus_type.add_links = of_link_to_suppliers; /* * Handle certain compatibles explicitly, since we don't want to create * platform_devices for every node in /reserved-memory with a -- 2.22.0.657.g960e92d24f-goog