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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 6E3A8C4363A for ; Thu, 8 Oct 2020 14:08:32 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EDBFD2184D for ; Thu, 8 Oct 2020 14:08:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="gWwGTaqT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EDBFD2184D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ipTwzFsYvLAhbyQDcm0XzaWKfaAhyKp+/pX24Up8pyA=; b=gWwGTaqTjypf3ahgiseYvcrvD +GCtGmZ6mkAmHYbt+oYUxbSUj5Hbo6ePKVLiP/VKoRDXPhbDAw8vVgtn/GVZUrK0Brzr9uHm+TAHE pal+toU/SHk/7pSawv164xq9zfLFZLdSM4hVLJq+ARKUb7+xs4qlHTku6kYGo0v8f/9/4OnKn8i2n 8O/9npH2j1QTRi0BrFC7zvIP/ItwlRwghdFx+VWcCOYe4VkLZUPpSHjkmKvnLLdWgLDL0J5zTD93k yj/OdN+BcE7yAi391r6Fm/MU67ay9eSlHG6cJkdPUYGT0ZgMd9rkalPSj3UU2vnf5T97BueZTRM+M AsmsufA9A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQWYj-0005KV-DF; Thu, 08 Oct 2020 14:06:17 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQWYg-0005KA-Lv for linux-arm-kernel@lists.infradead.org; Thu, 08 Oct 2020 14:06:15 +0000 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 7F2481063; Thu, 8 Oct 2020 07:06:08 -0700 (PDT) Received: from bogus (unknown [10.57.53.233]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EA9673F70D; Thu, 8 Oct 2020 07:06:05 -0700 (PDT) Date: Thu, 8 Oct 2020 15:05:58 +0100 From: Sudeep Holla To: "Rafael J. Wysocki" Subject: Re: [PATCH 0/2]cpufreq,topology,arm: disable FI for BL_SWITCHER Message-ID: <20201008140558.ovytcc34div3ih6m@bogus> References: <20200924123016.13427-1-ionela.voinescu@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20171215 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201008_100614_805604_B08243E3 X-CRM114-Status: GOOD ( 30.96 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux Kernel Mailing List , Will Deacon , Linux PM , Catalin Marinas , Sudeep Holla , "Rafael J. Wysocki" , Russell King - ARM Linux , Valentin Schneider , Viresh Kumar , Ionela Voinescu , Dietmar Eggemann , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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) -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel