From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751996AbbG2AJp (ORCPT ); Tue, 28 Jul 2015 20:09:45 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:58520 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750843AbbG2AJj convert rfc822-to-8bit (ORCPT ); Tue, 28 Jul 2015 20:09:39 -0400 From: "Rafael J. Wysocki" To: Tomeu Vizoso Cc: linux-kernel@vger.kernel.org, Stephen Warren , Javier Martinez Canillas , Mark Brown , Thierry Reding , linux-arm-kernel@lists.infradead.org, Dmitry Torokhov , devicetree@vger.kernel.org, Linus Walleij , linux-acpi@vger.kernel.org, Arnd Bergmann , linux-fbdev@vger.kernel.org, linux-usb@vger.kernel.org, Felipe Balbi , linux-pwm@vger.kernel.org, alsa-devel@alsa-project.org, Terje =?ISO-8859-1?Q?Bergstr=F6m?= , Len Brown , Rob Herring , David Airlie , Michael Turquette , linux-clk@vger.kernel.org, dmaengine@vger.kernel.org, Jean-Christophe Plagniol-Villard , Sebastian Reichel , Tomi Valkeinen , Grant Likely , Greg Kroah-Hartman , Alexandre Courbot , linux-pm@vger.kernel.org, Stephen Boyd , Wolfram Sang , Dan Williams , linux-gpio@vger.kernel.org, Vinod Koul , Liam Girdwood , dri-devel@lists.freedesktop.org, Lee Jones , linux-tegra@vger.kernel.org, Jaroslav Kysela , Takashi Iwai , Dmitry Eremin-Solenikov , Jingoo Han , David Woodhouse , Kishon Vijay Abraham I , linux-i2c@vger.kernel.org Subject: Re: [PATCH v2 0/22] On-demand device probing Date: Wed, 29 Jul 2015 02:36:33 +0200 Message-ID: <2554489.GlTphZsHuX@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.1.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1438089593-7696-1-git-send-email-tomeu.vizoso@collabora.com> References: <1438089593-7696-1-git-send-email-tomeu.vizoso@collabora.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, July 28, 2015 03:19:31 PM Tomeu Vizoso wrote: > Hello, > > I have a problem with the panel on my Tegra Chromebook taking longer > than expected to be ready during boot (Stéphane Marchesin reported what > is basically the same issue in [0]), and have looked into ordered > probing as a better way of solving this than moving nodes around in the > DT or playing with initcall levels and linking order. > > While reading the thread [1] that Alexander Holler started with his > series to make probing order deterministic, it occurred to me that it > should be possible to achieve the same by probing devices as they are > referenced by other devices. > > This basically reuses the information that is already implicit in the > probe() implementations, saving us from refactoring existing drivers or > adding information to DTBs. > > During review of v1 of this series Linus Walleij suggested that it > should be the device driver core to make sure that dependencies are > ready before probing a device. I gave this idea a try [2] but Mark Brown > pointed out to the logic duplication between the resource acquisition > and dependency discovery code paths (though I think it's fairly minor). > > To address that code duplication I experimented with Arnd's devm_probe > [3] concept of having drivers declare their dependencies instead of > acquiring them during probe, and while it worked [4], I don't think we > end up winning anything when compared to just probing devices on-demand > from resource getters. > > One remaining objection is to the "sprinkling" of calls to > fwnode_ensure_device() in the resource getters of each subsystem, but I > think it's the right thing to do given that the storage of resources is > currently subsystem-specific. > > We could avoid the above by moving resource storage into the core, but I > don't think there's a compelling case for that. > > I have tested this on boards with Tegra, iMX.6, Exynos and OMAP SoCs, > and these patches were enough to eliminate all the deferred probes > (except one in PandaBoard because omap_dma_system doesn't have a > firmware node as of yet). > > With this series I get the kernel to output to the panel in 0.5s, > instead of 2.8s. Can you trim your CC list somewhat, please? I'm definitely going to look at this, but not before then next week. Sorry about that. Thanks, Rafael