From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABB68C282DD for ; Mon, 10 Jun 2019 11:02:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87DF02082E for ; Mon, 10 Jun 2019 11:02:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389349AbfFJLC4 (ORCPT ); Mon, 10 Jun 2019 07:02:56 -0400 Received: from foss.arm.com ([217.140.110.172]:40672 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388982AbfFJLC4 (ORCPT ); Mon, 10 Jun 2019 07:02:56 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AC8F6337; Mon, 10 Jun 2019 04:02:55 -0700 (PDT) Received: from e107155-lin (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DB2553F557; Mon, 10 Jun 2019 04:04:34 -0700 (PDT) Date: Mon, 10 Jun 2019 12:02:50 +0100 From: Sudeep Holla To: Ulf Hansson Cc: Lorenzo Pieralisi , Mark Rutland , Linux ARM , "Rafael J . Wysocki" , Daniel Lezcano , "Raju P . L . S . S . S . N" , Amit Kucheria , Bjorn Andersson , Stephen Boyd , Niklas Cassel , Tony Lindgren , Kevin Hilman , Lina Iyer , Viresh Kumar , Vincent Guittot , Geert Uytterhoeven , Souvik Chakravarty , Sudeep Holla , Linux PM , linux-arm-msm , Linux Kernel Mailing List Subject: Re: [PATCH 15/18] drivers: firmware: psci: Support CPU hotplug for the hierarchical model Message-ID: <20190610110250.GD26602@e107155-lin> References: <20190513192300.653-1-ulf.hansson@linaro.org> <20190513192300.653-16-ulf.hansson@linaro.org> <20190607153114.GI15577@e107155-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Mon, Jun 10, 2019 at 12:21:47PM +0200, Ulf Hansson wrote: > On Fri, 7 Jun 2019 at 17:31, Sudeep Holla wrote: > > > > On Mon, May 13, 2019 at 09:22:57PM +0200, Ulf Hansson wrote: > > > When the hierarchical CPU topology is used and when a CPU has been put > > > offline (hotplug), that same CPU prevents its PM domain and thus also > > > potential master PM domains, from being powered off. This is because genpd > > > observes the CPU's attached device as being active from a runtime PM point > > > of view. > > > > > > To deal with this, let's decrease the runtime PM usage count by calling > > > pm_runtime_put_sync_suspend() of the attached struct device when putting > > > the CPU offline. Consequentially, we must then increase the runtime PM > > > usage count, while putting the CPU online again. > > > > > > > Why is this firmware/driver specific ? Why can't this be dealt in core > > pm-domain ? I am concerned that if any other architectures or firmware > > method decides to use this feature, this need to be duplicated there. > > What is the core pm-domain? Do you refer to the generic PM domain (genpd), no? > Sorry for my bad choice of names. I just wrote names as I understand rather than looking for exact match. But yes, I meant generic place where such ref-counting is done currently for other things. > In such case, this is not the job of genpd, but rather the opposite > (to *monitor* the reference count). > OK, I need to understand that then. > > > > The way I see this is pure reference counting and is hardware/firmware/ > > driver agnostic and can be made generic. > > As stated in the another reply, I would rather start with having more > things driver specific rather than generic. Later on we can always > consider to move/split things, when there are more users. > > In this particular case, the runtime PM reference counting is done on > the struct device*, that genpd returned via > dev_pm_domain_attach_by_name(). And because > dev_pm_domain_attach_by_name() is called from PSCI code, I decided to > keep this struct device* internal to PSCI. Sure, I understand your intent. I have just mentioned my thoughts/comments as I reviewed. -- Regards, Sudeep