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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 6D50EC4363C for ; Thu, 8 Oct 2020 15:18:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 188BB21D80 for ; Thu, 8 Oct 2020 15:18:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602170320; bh=s4NSqi3oLrSSCNnsLn1/qMfAevbZ94rdH8EfM/R1Pt0=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=2pusGrpxRstHJFaxC36ZNwEjQFQUybRnmyXuHtSM0mRzh0T2HceTHzdRe8qmTsfwC sGoZFl2hlClz2ELCzR6Gi4lTqFw0fSbrSpgKm52q/ly0KmuIGOMHS/moVcITz44AOh qgTvKVF7uabmD3dFLog9PivpbrK6oJgmvESS4YpM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730941AbgJHPSj (ORCPT ); Thu, 8 Oct 2020 11:18:39 -0400 Received: from mail-oo1-f68.google.com ([209.85.161.68]:33007 "EHLO mail-oo1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730650AbgJHPSi (ORCPT ); Thu, 8 Oct 2020 11:18:38 -0400 Received: by mail-oo1-f68.google.com with SMTP id r7so387652ool.0; Thu, 08 Oct 2020 08:18:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=lVTN3l7RCWCg+57rF3cB/zdsT9nZyrC1LZ/Pc3QOkPg=; b=h5q7OeANNvfFXdqJSfmu5Khf2vG/T318mcNU8r+JewYgqfP62BR0c8gEse+/rnD5wY uTS3eL1YlGdoOwoC/Ec+vMmjqMKW/x0W3pNTcnuomQ9OVsY/8JgK/X2mWB2Y5I7CPJFR 25UeSRhjtkEG1mfS3qF3x0B91O+++cFcI4TN2Ew5vJp+NghP0r++AQ5O/0JuKnQighGi prks4Ya3n7yOukWRgd2SRYEbHfo+NFLgvhjeJLZPtTXelll6Itq7/p5ICgCM6Lu1L7ww uMcriwNkVjCw7y49CGTMsuZO4OCW1imdXL9TJAQTi6QzaJLoRteOo8eCN3CuVOKX1s9x +n6g== X-Gm-Message-State: AOAM53314IHZt6DIajVG4ThJaP3wq9s3gSLTvJUvenjx7ivkd9M/4cKq wW4Q9f42kaUJW+FdmPvGHFmAXz4Ms12xyzQMw0aRBRwk X-Google-Smtp-Source: ABdhPJwdTaCWeEKKtUZT0Fd4ttSycfvOA7vXKrn7kpF0QR9Q67ObsRAossur3ThMA7cjZYizHClXPKC9I5fu/d/hVwo= X-Received: by 2002:a4a:d44:: with SMTP id 65mr5852302oob.44.1602170316044; Thu, 08 Oct 2020 08:18:36 -0700 (PDT) MIME-Version: 1.0 References: <20200924123016.13427-1-ionela.voinescu@arm.com> <20201008140558.ovytcc34div3ih6m@bogus> In-Reply-To: <20201008140558.ovytcc34div3ih6m@bogus> From: "Rafael J. Wysocki" Date: Thu, 8 Oct 2020 17:18:25 +0200 Message-ID: Subject: Re: [PATCH 0/2]cpufreq,topology,arm: disable FI for BL_SWITCHER To: Sudeep Holla , Ionela Voinescu Cc: "Rafael J. Wysocki" , Catalin Marinas , Will Deacon , Russell King - ARM Linux , "Rafael J. Wysocki" , Viresh Kumar , Dietmar Eggemann , Valentin Schneider , Linux PM , Linux ARM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 8, 2020 at 4:06 PM Sudeep Holla wrote: > > On Wed, Oct 07, 2020 at 04:34:44PM +0200, Rafael J. Wysocki wrote: > > On Thu, Sep 24, 2020 at 2:30 PM Ionela Voinescu wrote: > > > > > > This series is the result of the discussions ([1], [2]) around the > > > complications that the BL_SWITCHER poses when it comes to Frequency > > > Invariance (FI) and it aims to restart the discussions. > > > > > > To properly scale its per-entity load-tracking signals, the task > > > scheduler needs to be given a frequency scale factor, i.e. some image of > > > the current frequency the CPU is running at, relative to its maximum > > > frequency. > > > > > > But (reiterating the message in the changelog of patch 2/2), big.LITTLE > > > switching complicates the setting of a correct cpufreq-based frequency > > > invariance scale factor due to (as observed in > > > drivers/cpufreq/vexpress-spc-cpufreq.c): > > > - Incorrect current and maximum frequencies as a result of the > > > exposure of a virtual frequency table to the cpufreq core, > > > - Missed updates as a result of asynchronous frequency adjustments > > > caused by frequency changes in other CPU pairs. > > > More information on this feature can be found at [3]. > > > > > > Given that its functionality is atypical in regards to FI and that this > > > is an old technology, patch 2/2 disable FI for when big.LITTLE switching > > > is configured in to prevent incorrect scale setting. > > > > > > For this purpose patch 1/2 changes the way arch_set_freq_scale() is > > > defined in architecture code which brings it in line with the logic of > > > other architectural function definitions while allowing for less invasive > > > filtering of FI support. > > > > > > In the discussions at [2], three possible solutions were suggested: > > > - (1) conditioning FI by !CONFIG_BL_SWITCHER > > > - (2) leave as is with note in driver specifying this FI broken > > > functionality > > > - (3) removing full BL_SWITCHER support > > > > > > This series restructures the solution at (1). The reason for it is that > > > the new patch limits the ifdef filtering to the arm topology include file, > > > a location where frequency invariance functions are defined. Therefore, > > > this seems more appropriate given that the b.L switcher is an arm > > > technology and that the new FI filtering location seems more natural for > > > conditioned FI disabling. > > > > > > Solutions (2) and (3) were not implemented given that there might be some > > > remaining users of this technology (Samsung Chromebook 2 - Samsung Exynos > > > 5 Octa 5420, Samsung Exynos 5 Octa 5800) and therefore leaving this > > > broken (2) seems equally bad to removing support for it (3). > > > > > > [1] https://lore.kernel.org/lkml/20200701090751.7543-5-ionela.voinescu@arm.com/ > > > [2] https://lore.kernel.org/lkml/20200722093732.14297-4-ionela.voinescu@arm.com/ > > > [3] https://lwn.net/Articles/481055/ > > > > I can take this set with the ACKs from Viresh if that's fine by > > everyone. Catalin? Sudeep? > > Acked-by: Sudeep Holla (BL_SWITCHER and topology parts) OK, the series has been applied as 5.10 material, thanks!