From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753610Ab2CUDKg (ORCPT ); Tue, 20 Mar 2012 23:10:36 -0400 Received: from wolverine02.qualcomm.com ([199.106.114.251]:63404 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750833Ab2CUDKf (ORCPT ); Tue, 20 Mar 2012 23:10:35 -0400 X-IronPort-AV: E=McAfee;i="5400,1158,6655"; a="171996452" Message-ID: <4F6946AA.4070201@codeaurora.org> Date: Tue, 20 Mar 2012 20:10:34 -0700 From: Saravana Kannan User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:11.0) Gecko/20120312 Thunderbird/11.0 MIME-Version: 1.0 To: "Turquette, Mike" CC: Shawn Guo , Paul Walmsley , Russell King , Linus Walleij , patches@linaro.org, Magnus Damm , Sascha Hauer , Mark Brown , Stephen Boyd , linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org, Jeremy Kerr , linux-arm-kernel@lists.infradead.org, Arnd Bergman Subject: Re: [PATCH v7 2/3] clk: introduce the common clock framework References: <1331878280-2758-1-git-send-email-mturquette@linaro.org> <1331878280-2758-3-git-send-email-mturquette@linaro.org> <20120320140220.GE32469@S2101-09.ap.freescale.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/20/2012 04:53 PM, Turquette, Mike wrote: > On Tue, Mar 20, 2012 at 10:46 AM, Saravana Kannan > wrote: >> On Tue, March 20, 2012 7:02 am, Shawn Guo wrote: >>> On Thu, Mar 15, 2012 at 11:11:19PM -0700, Mike Turquette wrote: >>> ... >>>> +struct clk_ops { >>>> + int (*prepare)(struct clk_hw *hw); >>>> + void (*unprepare)(struct clk_hw *hw); >>>> + int (*enable)(struct clk_hw *hw); >>>> + void (*disable)(struct clk_hw *hw); >>>> + int (*is_enabled)(struct clk_hw *hw); >>>> + unsigned long (*recalc_rate)(struct clk_hw *hw, >>>> + unsigned long parent_rate); >>> >>> I believe I have heard people love the interface with parent_rate >>> passed in. I love that too. But I would like to ask the same thing >>> on .round_rate and .set_rate as well for the same reason why we have >>> it for .recalc_rate. >> >> In my case, for most clocks, set rate involves reparenting. So, what does >> passing parent_rate for these even mean? Passing parent_rate seems more >> apt for recalc_rate since it's called when the parent rate changes -- so, >> the actual parent itself is not expected to change. > > From my conversations with folks across many platforms, I think that > the way your clock tree expects to change rates is the exception, not > the rule. As such you should just ignore the parent_rate parameter as > it useless to you. > >> I could ignore the parameter, but just wondering how many of the others >> see value in this. And if we do add this parameter, it shouldn't be made >> mandatory for the platform driver to use it (due to other assumptions the >> clock framework might make). > > From my rough census of folks that actually need .set_rate support, I > think that everyone except MSM could benefit from this. Your concept > of clk_set_rate is everyone else's clk_set_parent. To clarify, MSM's set parent is a subset of steps needed to be done to finish set parent. So, it's not that we just randomly decided to swap the meanings of these two functions. Also, I think don't think the difference in view of set_rate is due to the difference in the clock trees between platforms with complicated trees. I think it's more because of who actually decides the rates for the clock tree. It looks like some platforms pick a top-down approach to deciding the rates of the clock tre while others pick a bottom-up approach. > Ignoring the new parameter should cause you no harm. As long as this is guaranteed, I have no problems with Shawn's suggestion. > It does make me > wonder if it would be a good idea to pass in the parent rate for > .set_parent, which is analogous to .set_rate in many ways. I need to think a bit more about this. -Saravana -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.