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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 60E71C433EF for ; Tue, 19 Jun 2018 10:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 266E520874 for ; Tue, 19 Jun 2018 10:02:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 266E520874 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757194AbeFSKCe (ORCPT ); Tue, 19 Jun 2018 06:02:34 -0400 Received: from foss.arm.com ([217.140.101.70]:46338 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757174AbeFSKCa (ORCPT ); Tue, 19 Jun 2018 06:02:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2E5DB15AB; Tue, 19 Jun 2018 03:02:30 -0700 (PDT) Received: from e108498-lin.cambridge.arm.com (e108498-lin.cambridge.arm.com [10.1.211.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3A20F3F25D; Tue, 19 Jun 2018 03:02:26 -0700 (PDT) Date: Tue, 19 Jun 2018 11:02:24 +0100 From: Quentin Perret To: Juri Lelli Cc: Pavan Kondeti , peterz@infradead.org, rjw@rjwysocki.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joelaf@google.com, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org Subject: Re: [RFC PATCH v3 10/10] arch_topology: Start Energy Aware Scheduling Message-ID: <20180619100224.GT17720@e108498-lin.cambridge.arm.com> References: <20180521142505.6522-1-quentin.perret@arm.com> <20180521142505.6522-11-quentin.perret@arm.com> <20180619091841.GD9208@codeaurora.org> <20180619094002.GR17720@e108498-lin.cambridge.arm.com> <20180619094714.GA13617@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180619094714.GA13617@localhost.localdomain> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 19 Jun 2018 at 11:47:14 (+0200), Juri Lelli wrote: > On 19/06/18 10:40, Quentin Perret wrote: > > Hi Pavan, > > > > On Tuesday 19 Jun 2018 at 14:48:41 (+0530), Pavan Kondeti wrote: > > [...] > > > > There seems to be a sysfs interface exposed by this driver to change cpu_scale. > > > Should we worry about it? I don't know what is the usecase for changing the > > > cpu_scale from user space. > > > > This is something I've been wondering as well. TBH, I'm not sure what to > > do in this case. And I'm not sure to know what is the use-case either. > > Debugging purpose I assume ? > > > > Juri, did you have a specific use-case for this feature when the > > arch_topology driver was first introduced ? Or was it just to align > > with the existing arm/arm64 code ? > > It was requested (IIRC) because DT might have bogus values and not be > easily modifiable. So, this is another way to get things right for your > platform at runtime. Right, but that also allows you to set different capacities to CPUs inside the same freq domain, which isn't supported by the EM framework, at least for now. So I would prefer to assume that your values in DT must to be correct to use EAS, and leave the code as-is for now.