Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753099AbdHIKPo (ORCPT ); Wed, 9 Aug 2017 06:15:44 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:45566 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752959AbdHIKPm (ORCPT ); Wed, 9 Aug 2017 06:15:42 -0400 Cc: Sudeep Holla , ALKML , LKML , DTML , Roy Franz , Harb Abdulhamid , Nishanth Menon , Arnd Bergmann , Loc Ho , Alexey Klimov , Ryan Harkin , Jassi Brar , "Rafael J. Wysocki" , linux-pm@vger.kernel.org Subject: Re: [PATCH v2 17/18] cpufreq: add support for CPU DVFS based on SCMI message protocol To: Viresh Kumar References: <1501857104-11279-1-git-send-email-sudeep.holla@arm.com> <1501857104-11279-18-git-send-email-sudeep.holla@arm.com> <20170809041840.GH28857@vireshk-i7> <97497123-2c24-6297-2d12-4f407d101b66@arm.com> <20170809100651.GA29383@vireshk-i7> From: Sudeep Holla Organization: ARM Message-ID: Date: Wed, 9 Aug 2017 11:15:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170809100651.GA29383@vireshk-i7> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2616 Lines: 85 On 09/08/17 11:06, Viresh Kumar wrote: > On 09-08-17, 10:59, Sudeep Holla wrote: >> On 09/08/17 05:18, Viresh Kumar wrote: > >>> This stores the same handle pointer which is stored in the global variable >>> below. Right? Why keep a local variable here at all ? >> >> Yes, you are right. Initially, started with just private pointers and >> then added global. I was thinking of calling devm_scmi_handle_get per >> policy to reflect the refcount correctly and drop global variable. Let >> me know what you think. > > A refcount of 1 should be fine as well, i.e. For the cpufreq driver. Why would > SCMI care if we manage multiple policies here ? Unless it makes something within > SCMI core better. > Not really, just we can get rid of global pointer which may be need in system with multiple scmi instances, but that's long way to go. >>> This is something special which is used only when we are returning indexes and >>> I am not sure if this will have benefit here. I will rather return 0 here. >>> That's what other drivers are doing. >> >> Indeed had 0 initially but changed as per Juri's suggestion. > > Maybe he suggested doing that in the fast switch routine ? As that's the normal > protocol there. Though I have sent a patch today to propose using 0 there as > well (you cc'd). > Yes, saw that. I have changed both to 0 for now. I will watch that thread and update if necessary before next posting. >> But is 0 >> treated as failure and still running at current OPP ? > > You have used that in the ->get() routine. So the OPP isn't changing, but we are > just trying to fetch it. cpufreq core doesn't do a lot with the value returned > from here, but at one place we break early if 0 is returned. And so all drivers > are returning that. > Agreed, I assumed _INVALID is new thing and changed at both target_indes and fast_switch. >> and not 0KHz I assume. > > Yeah, 0 KHz is dead CPU really :) > :) >>> I suppose any CPU can change the frequency of any other CPU here, right? You >>> must set policy->dvfs_possible_from_any_cpu = true, from ->init() then. >>> >> >> OK, I missed to see something like that exists, will do. > > Fairly recent stuff, present in pm/linux-next only. > Oh OK. >>>> + /* >>>> + * But we need OPP table to function so if it is not there let's >>>> + * give platform code chance to provide it for us. >>>> + */ >>> >>> How are we getting the OPPs? DT or non DT ? >>> >> >> Non DT :), from the firmware. > > I would improve the above comment in that case to clearly say that OPPs are > added by the platform, lets wait for it. > Done -- Regards, Sudeep