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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 40A79C7618F for ; Tue, 16 Jul 2019 23:43:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 018C52187F for ; Tue, 16 Jul 2019 23:43:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563320639; bh=SLwAQqynI30zO27AL0iFcVL0NVEoCSYm5URkflhUQvI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=zhhEiLXzAaqLHxtFbC9XZ1+nVNTc5kiZTl0Q4gLFA5qDVkOi/b4AGo43FOVBqLVAM ildWOFQ7tl2g735U6iwzyW9yn5cyon+guO2Zgd1Hl7F34xe68QJJLGL+8nqyen3U0y 8/zqUo7/RV4MOVQ1W/5K5jee/Rm7V42KxdpIBELo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388822AbfGPXn5 (ORCPT ); Tue, 16 Jul 2019 19:43:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:56180 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728681AbfGPXn5 (ORCPT ); Tue, 16 Jul 2019 19:43:57 -0400 Received: from mail-qk1-f178.google.com (mail-qk1-f178.google.com [209.85.222.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CCC1421880; Tue, 16 Jul 2019 23:43:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563320635; bh=SLwAQqynI30zO27AL0iFcVL0NVEoCSYm5URkflhUQvI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=ornP4q1BOw0Jh4HjheQaQeKMpo3d1tSWOCa33P5gqeF5t+wxU0dnhaW1DPUW3FREs hJhPeNm9YGCTsV1XKq05ryMOfYqh8miGlcV3EOq8BPyuztHb61AO8s8v23r2MHj56l MfWI2q2ko5rQAH0PNa/u5RF5ApzYLWMTv5qU3svg= Received: by mail-qk1-f178.google.com with SMTP id g18so16045170qkl.3; Tue, 16 Jul 2019 16:43:55 -0700 (PDT) X-Gm-Message-State: APjAAAUWSPNfYSB4ypNM+e2wGYTq/lsh3fRHTi5HPwCVLoFAOjTJ2GgS hIyg9j4wDaUiHYlRnGGAv1sruCOoj4GwWRWrTw== X-Google-Smtp-Source: APXvYqxpbCTn4f4rGmNKCBuHJcl3ViBirm9Qd2/tmIyb6NeyDwASnc2Y4bhGWee0FDMKQgC5YBjIHPNompJ82Znv8+E= X-Received: by 2002:a37:a010:: with SMTP id j16mr24377204qke.152.1563320635024; Tue, 16 Jul 2019 16:43:55 -0700 (PDT) MIME-Version: 1.0 References: <20190712235245.202558-1-saravanak@google.com> <20190712235245.202558-3-saravanak@google.com> In-Reply-To: <20190712235245.202558-3-saravanak@google.com> From: Rob Herring Date: Tue, 16 Jul 2019 17:43:44 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 02/11] of/platform: Add functional dependency link from DT bindings To: Saravana Kannan Cc: Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand , Jonathan Corbet , devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" , David Collins , Android Kernel Team , Linux Doc Mailing List 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 On Fri, Jul 12, 2019 at 5:52 PM Saravana Kannan wrote: > > 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 | 57 +++++++++++++++++++ > 2 files changed, 62 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..0930f9f89571 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -509,6 +509,62 @@ int of_platform_default_populate(struct device_node *root, > } > EXPORT_SYMBOL_GPL(of_platform_default_populate); > > +static int of_link_binding(struct device *dev, > + const char *binding, const char *cell) > +{ > + struct of_phandle_args sup_args; > + struct platform_device *sup_dev; > + unsigned int i = 0, links = 0; > + u32 dl_flags = DL_FLAG_AUTOPROBE_CONSUMER; > + > + while (!of_parse_phandle_with_args(dev->of_node, binding, cell, i, > + &sup_args)) { > + i++; > + sup_dev = of_find_device_by_node(sup_args.np); > + of_node_put(sup_args.np); > + if (!sup_dev) > + continue; > + if (device_link_add(dev, &sup_dev->dev, dl_flags)) > + links++; > + put_device(&sup_dev->dev); > + } > + if (links < i) > + return -ENODEV; > + return 0; > +} > + > +static bool of_devlink; > +core_param(of_devlink, of_devlink, bool, 0); > + > +/* > + * List of bindings and their cell names (use NULL if no cell names) from which > + * device links need to be created. > + */ > +static const char * const link_bindings[] = { > + "clocks", "#clock-cells", > + "interconnects", "#interconnect-cells", > +}; > + > +static int of_link_to_suppliers(struct device *dev) > +{ > + unsigned int i = 0; > + bool done = true; > + > + if (!of_devlink) > + return 0; > + if (unlikely(!dev->of_node)) > + return 0; > + > + for (i = 0; i < ARRAY_SIZE(link_bindings) / 2; i++) > + if (of_link_binding(dev, link_bindings[i * 2], > + link_bindings[i * 2 + 1])) > + done = false; Given the pending addition of regulators I think this should be structured a bit differently so that we abstract out the matching and phandle look-up so there's a clean separation of binding specifics. It's kind of messy with 2 patterns to parse already and if we added a 3rd? I would iterate over the properties as you do for regulators in both cases and for each property call a binding specific match function. The common pattern can of course be a common function. Let me know if that makes sense. If not I can try to flesh it out some more. Rob