From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lorenzo Pieralisi Subject: Re: [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver Date: Mon, 16 Apr 2018 13:30:20 +0100 Message-ID: <20180416123019.GA9341@e107981-ln.cambridge.arm.com> References: <3f3b3b7a-3b74-aee2-2fac-f2759babe3f0@arm.com> <939f7943-feec-aaa2-3bd3-59a6618330c0@linaro.org> <20180416073729.GA4244@vireshk-i7> <0a3164f9-4738-e24e-6ed0-2c75024c304c@linaro.org> <20180416093747.GB4244@vireshk-i7> <4abf0d97-d2b8-46ab-3c05-4a11510ac3fe@linaro.org> <20180416095006.GC4244@vireshk-i7> <20180416101021.GD4244@vireshk-i7> <1c61128a-dea6-b12c-4cd8-ef53a5c8628d@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1c61128a-dea6-b12c-4cd8-ef53a5c8628d@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: Daniel Lezcano Cc: Viresh Kumar , Sudeep Holla , edubezval@gmail.com, kevin.wangtao@linaro.org, leo.yan@linaro.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, javi.merino@kernel.org, rui.zhang@intel.com, daniel.thompson@linaro.org, linux-pm@vger.kernel.org, Amit Daniel Kachhap List-Id: linux-pm@vger.kernel.org On Mon, Apr 16, 2018 at 02:10:30PM +0200, Daniel Lezcano wrote: > On 16/04/2018 12:10, Viresh Kumar wrote: > > On 16-04-18, 12:03, Daniel Lezcano wrote: > >> On 16/04/2018 11:50, Viresh Kumar wrote: > >>> On 16-04-18, 11:45, Daniel Lezcano wrote: > >>>> Can you elaborate a bit ? I'm not sure to get the point. > >>> > >>> Sure. With your current code on Hikey960 (big/LITTLE), you end up > >>> creating two cooling devices, one for the big cluster and one for > >>> small cluster. Which is the right thing to do, as we also have two > >>> cpufreq cooling devices. > >>> > >>> But with the change Sudeep is referring to, the helper you used to get > >>> cluster id will return 0 (SoC id) for all the 8 CPUs. So your code > >>> will end up creating a single cpuidle cooling device for all the CPUs. > >>> Which would be wrong. > >> > >> Is the semantic of topology_physical_package_id changing ? > > > > That's what I understood from his email. > > > >> I don't > >> understand the change Sudeep is referring to. > > Actually there is no impact with the change Sudeep is referring to. It > is for ACPI, we are DT based. Confirmed with Jeremy. > > So AFAICT, it is not a problem. It is a problem - DT or ACPI alike. Sudeep was referring to the notion of "cluster" that has no architectural meaning whatsoever and using topology_physical_package_id() to detect a "cluster" was/is/will always be the wrong thing to do. The notion of cluster must not appear in the kernel at all, it has no architectural meaning. I understand you need to group CPUs but that has to be done in a different way, through cooling devices, thermal domains or power domains DT/ACPI bindings but not by using topology masks. You should be able to figure out this week at OSPM the reasoning behind what I am saying above. Cheers, Lorenzo