From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752532AbdA1Xkc (ORCPT ); Sat, 28 Jan 2017 18:40:32 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:41474 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751471AbdA1XkX (ORCPT ); Sat, 28 Jan 2017 18:40:23 -0500 Date: Sat, 28 Jan 2017 23:39:11 +0000 From: Russell King - ARM Linux To: Guenter Roeck Cc: Dmitry Torokhov , Michael Turquette , Stephen Boyd , Viresh Kumar , Andy Shevchenko , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] clk: add more managed APIs Message-ID: <20170128233911.GO27312@n2100.armlinux.org.uk> References: <20170128184047.GA24957@dtor-ws> <20170128190309.GN27312@n2100.armlinux.org.uk> <20170128192207.GA38136@dtor-ws> <64ed0890-14f6-42ff-66b1-60f7b3d7d02f@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64ed0890-14f6-42ff-66b1-60f7b3d7d02f@roeck-us.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 28, 2017 at 01:44:35PM -0800, Guenter Roeck wrote: > On 01/28/2017 11:22 AM, Dmitry Torokhov wrote: > >Guenter, I know you are a coccinelle wizard, can you cook a script that > >can find current users of clk_enable() in probe paths? Then we can make > >informed decision on devm_clk_enable. > > > > Questionable use: > drivers/input/keyboard/st-keyscan.c clk_enable() without preceding clk_prepare() - buggy. > > clk_enable() in probe, clk_disable() in remove: > drivers/i2c/busses/i2c-tegra.c Could be converted to use clk_prepare_enable() or clk_prepare() depending on i2c_dev->is_multimaster_mode in the initialisation path (and their devm_* equivalents.) > drivers/media/platform/exynos4-is/fimc-core.c > drivers/media/platform/exynos4-is/mipi-csis.c Looks like it does a sequence of: devm_clk_get() clk_prepare() clk_set_rate() clk_enable() which seems a little wrong - clk_set_rate() should be before clk_prepare() if you care about not having the clock output. Remember that clk_prepare() _may_ result in the clock output being enabled. So these two look buggy, and when fixed could use devm_clk_prepare_enable(). > drivers/thermal/spear_thermal.c clk_enable() without a preceding clk_prepare(). Buggy driver. > drivers/usb/musb/am35x.c Ditto. > drivers/usb/musb/davinci.c Ditto. > Not that many. A quick browse suggests that clk_enable()/clk_disable() > is more commonly used to temporarily enable the clock while needed. So out of all those, there's probably only _one_ which is legit - the rest are all technically buggy. Given that, I'd say there's real reason _not_ to provide devm_clk_enable() to persuade people to use the correct interfaces in the probe path. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.