From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH v4 3/6] clk: introduce the common clock framework Date: Wed, 04 Jan 2012 08:32:31 -0600 Message-ID: <4F0462FF.1000308@gmail.com> References: <1323834838-2206-1-git-send-email-mturquette@linaro.org> <1323834838-2206-4-git-send-email-mturquette@linaro.org> <20120104021541.GI2414@b20223-02.ap.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-gy0-f174.google.com ([209.85.160.174]:48809 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753763Ab2ADOci (ORCPT ); Wed, 4 Jan 2012 09:32:38 -0500 In-Reply-To: <20120104021541.GI2414@b20223-02.ap.freescale.net> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Richard Zhao Cc: "Turquette, Mike" , andrew@lunn.ch, linaro-dev@lists.linaro.org, eric.miao@linaro.org, grant.likely@secretlab.ca, Colin Cross , jeremy.kerr@canonical.com, linux@arm.linux.org.uk, sboyd@quicinc.com, magnus.damm@gmail.com, dsaxena@linaro.org, linux-arm-kernel@lists.infradead.org, arnd.bergmann@linaro.org, patches@linaro.org, Thomas Gleixner , linux-omap@vger.kernel.org, richard.zhao@linaro.org, shawn.guo@freescale.com, paul@pwsan.com, linus.walleij@stericsson.com, broonie@opensource.wolfsonmicro.com, linux-kernel@vger.kernel.org, amit.kucheria@linaro.org, skannan@quicinc.com On 01/03/2012 08:15 PM, Richard Zhao wrote: > On Fri, Dec 16, 2011 at 04:45:48PM -0800, Turquette, Mike wrote: >> On Wed, Dec 14, 2011 at 5:18 AM, Thomas Gleixner wrote: >>> On Tue, 13 Dec 2011, Mike Turquette wrote: snip >>>> +/** >>>> + * clk_init - initialize the data structures in a struct clk >>>> + * @dev: device initializing this clk, placeholder for now >>>> + * @clk: clk being initialized >>>> + * >>>> + * Initializes the lists in struct clk, queries the hardware for the >>>> + * parent and rate and sets them both. Adds the clk to the sysfs tree >>>> + * topology. >>>> + * >>>> + * Caller must populate clk->name and clk->flags before calling >>> >>> I'm not too happy about this construct. That leaves struct clk and its >>> members exposed to the world instead of making it a real opaque >>> cookie. I know from my own painful experience, that this will lead to >>> random fiddling in that data structure in drivers and arch code just >>> because the core code has a shortcoming. >>> >>> Why can't we make struct clk a real cookie and confine the data >>> structure to the core code ? >>> >>> That would change the init call to something like: >>> >>> struct clk *clk_init(struct device *dev, const struct clk_hw *hw, >>> struct clk *parent) >>> >>> And have: >>> struct clk_hw { >>> struct clk_hw_ops *ops; >>> const char *name; >>> unsigned long flags; >>> }; >>> >>> Implementers can do: >>> struct my_clk_hw { >>> struct clk_hw hw; >>> mydata; >>> }; >>> >>> And then change the clk ops callbacks to take struct clk_hw * as an >>> argument. > We have to define static clocks before we adopt DT binding. > If clk is opaque and allocate memory in clk core, it'll make hard > to define static clocks. And register/init will pass a long parameter > list. DT is not a prerequisite for having dynamically created clocks. You can make clock init dynamic without DT. What data goes in struct clk vs. struct clk_hw could change over time. So perhaps we can start with some data in clk_hw and plan to move it to struct clk later. Even if almost everything ends up in clk_hw initially, at least the structure is in place to have common, core-only data separate from platform data. What is the actual data you need to be static and accessible to the platform code? A ptr to parent clk is the main thing I've seen for static initialization. So make the parent ptr be struct clk_hw* and allow the platforms to access. Rob