Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965023Ab3CNRyM (ORCPT ); Thu, 14 Mar 2013 13:54:12 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:37521 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964907Ab3CNRyH (ORCPT ); Thu, 14 Mar 2013 13:54:07 -0400 Message-ID: <51420EBB.7080503@wwwdotorg.org> Date: Thu, 14 Mar 2013 11:54:03 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Bill Huang CC: Peter De Schrijver , "mturquette@linaro.org" , "patches@linaro.org" , "linux-kernel@vger.kernel.org" , Russell King - ARM Linux , "linaro-dev@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC 1/1] clk: Add notifier support in clk_prepare_enable/clk_disable_unprepare References: <1363091861-21534-1-git-send-email-bilhuang@nvidia.com> <20130312134032.GU4977@n2100.arm.linux.org.uk> <1363139273.21694.11.camel@bilhuang-vm1> <514003B6.8020904@wwwdotorg.org> <1363151317.3311.9.camel@bilhuang-vm1> <51400D9D.9060305@wwwdotorg.org> <1363153204.3311.14.camel@bilhuang-vm1> <5140C12A.4060900@wwwdotorg.org> <1363227311.3311.30.camel@bilhuang-vm1> <20130314092132.GE18519@tbergstrom-lnx.Nvidia.com> <1363253287.3311.32.camel@bilhuang-vm1> In-Reply-To: <1363253287.3311.32.camel@bilhuang-vm1> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-9 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1352 Lines: 27 On 03/14/2013 03:28 AM, Bill Huang wrote: > On Thu, 2013-03-14 at 17:21 +0800, Peter De Schrijver wrote: >> On Thu, Mar 14, 2013 at 03:15:11AM +0100, Bill Huang wrote: >> >>> I don't think deferring will work either, considering the usage of DVFS, >>> device voltage is tightly coupled with frequency, when clock rate is >>> about to increase, we have to boost voltage first and we can lower the >>> voltage after the clock rate has decreased. All the above sequence have >>> to be guaranteed or you might crash, so deferring not only make thing >>> complicated in controlling the order but also hurt performance. >> >> But we could use notifiers in clk_prepare/clk_unprepare to set the voltage no? >> As clk_prepare/clk_unprepare have to be called before clk_enable or after >> clk_disable, the voltage can be raised to a safe level, before the clock >> becomes active. > > Thanks Peter, actually I'm just about to propose my v2 RFC which add > notifier in clk_prepare/clk_unprepare. Can't clk_set_rate() be called while the clock is prepared, or even enabled? I don't see how your proposal would work. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/