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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 A6B47C433E0 for ; Thu, 30 Jul 2020 09:10:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AB0D20809 for ; Thu, 30 Jul 2020 09:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728528AbgG3JKY (ORCPT ); Thu, 30 Jul 2020 05:10:24 -0400 Received: from foss.arm.com ([217.140.110.172]:36742 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726819AbgG3JKX (ORCPT ); Thu, 30 Jul 2020 05:10:23 -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 A42C7D6E; Thu, 30 Jul 2020 02:10:22 -0700 (PDT) Received: from bogus (unknown [10.37.12.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 637473F792; Thu, 30 Jul 2020 02:10:20 -0700 (PDT) Date: Thu, 30 Jul 2020 10:10:14 +0100 From: Sudeep Holla To: Viresh Kumar Cc: Lukasz Luba , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, cristian.marussi@arm.com, rjw@rjwysocki.net, Sudeep Holla Subject: Re: [PATCH 0/4] CPUFreq statistics retrieved by drivers Message-ID: <20200730091014.GA13158@bogus> References: <20200729151208.27737-1-lukasz.luba@arm.com> <20200730085333.qubrsv7ufqninihd@vireshk-mac-ubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200730085333.qubrsv7ufqninihd@vireshk-mac-ubuntu> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Thu, Jul 30, 2020 at 02:23:33PM +0530, Viresh Kumar wrote: > On 29-07-20, 16:12, Lukasz Luba wrote: > > The existing CPUFreq framework does not tracks the statistics when the > > 'fast switch' is used or when firmware changes the frequency independently > > due to e.g. thermal reasons. However, the firmware might track the frequency > > changes and expose this to the kernel. > > > > This patch set aims to introduce CPUfreq statistics gathered by firmware > > and retrieved by CPUFreq driver. It would require a new API functions > > in the CPUFreq, which allows to poke drivers to get these stats. > > > > The needed CPUFreq infrastructure is in patch 1/4, patch 2/4 extends > > ARM SCMI protocol layer, patches 3/4, 4/4 modify ARM SCMI CPUFreq driver. > > Are you doing this for the fast switch case or because your platform > actually runs at frequencies which may be different from what cpufreq > core has requested ? > I think so. > I am also not sure what these tables should represent, what the > cpufreq core has decided for the CPUs or the frequencies we actually > run at, as these two can be very different for example if the hardware > runs at frequencies which don't match exactly to what is there in the > freq table. I believe these are rather to show what cpufreq and its > governors are doing with the CPUs. > Exactly, I raised similar point in internal discussion and asked Lukasz to take up the same on the list. I assume it was always what cpufreq requested rather than what was delivered. So will we break the userspace ABI if we change that is the main question. > Over that I would like the userspace stats to work exactly as the way > they work right now, i.e. capture all transitions from one freq to > other, not just time-in-state. Also resetting of the stats from > userspace for example. All allocation and printing of the data must be > done from stats core, the only thing which the driver would do at the > end is updating the stats structure and nothing more. Instead of > reading all stats from the firmware, it will be much easier if you can > just get the information from the firmware whenever there is a > frequency switch and then we can update the stats the way it is done > right now. And that would be simple. > Good point, but notifications may not be lightweight. If that is no good, alternatively, I suggested to keep these firmware stats in a separate debugfs. Thoughts ? -- Regards, Sudeep