From patchwork Thu Sep 24 12:30:14 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ionela Voinescu X-Patchwork-Id: 11797171 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E751559D for ; Thu, 24 Sep 2020 12:32:28 +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 947D8221EB for ; Thu, 24 Sep 2020 12:32:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="xkK4YS/j" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 947D8221EB 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-arm-kernel-bounces+patchwork-linux-arm=patchwork.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:MIME-Version:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Owner; bh=UhPq8END5QtFvbVKDYEjEEcRdgpkLg3Ijf28ffj2MVg=; b=xkK4YS/jZ1e5VB15L8b6obnsc0 TVyfQwWpNAntcsa3hQRlcscJvgwItZhKkLRn2iPNQyKhWo/cqAQjI7X3n7lyg8EJX/VoIBPE3ZNed o8LluCOjnMlNnhT7XKjh/KzwXElVz6f/iYbkvgRKtc6bgf6An67cI5lidVakjIBnArqfu+twTcUtn GWC6l+TtOf5B/nJvX65E1pfZhACbrV1dkExcF6BRSVVcoXmg94OQF0B3vdX0hfU7SSCeQ1LzV9pYU 30Iw5oFMhgh18jaNBsoCgfx4qjspDtVyi9qOdwTzKLIpJzfjH5mZmsEj3uDTEP4AnH9DuWMS2YIpu p43AN+Fg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kLQOf-0000m6-Cz; Thu, 24 Sep 2020 12:30:49 +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 1kLQOc-0000kd-DY for linux-arm-kernel@lists.infradead.org; Thu, 24 Sep 2020 12:30:47 +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 A9515113E; Thu, 24 Sep 2020 05:30:43 -0700 (PDT) Received: from e108754-lin.cambridge.arm.com (unknown [10.1.199.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 1DC063F73B; Thu, 24 Sep 2020 05:30:42 -0700 (PDT) From: Ionela Voinescu To: catalin.marinas@arm.com, sudeep.holla@arm.com, will@kernel.org, linux@armlinux.org.uk, rjw@rjwysocki.net, viresh.kumar@linaro.org Subject: [PATCH 0/2]cpufreq,topology,arm: disable FI for BL_SWITCHER Date: Thu, 24 Sep 2020 13:30:14 +0100 Message-Id: <20200924123016.13427-1-ionela.voinescu@arm.com> X-Mailer: git-send-email 2.17.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200924_083046_574312_FCBB8E0F X-CRM114-Status: GOOD ( 16.63 ) X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [217.140.110.172 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 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-pm@vger.kernel.org, linux-kernel@vger.kernel.org, valentin.schneider@arm.com, ionela.voinescu@arm.com, dietmar.eggemann@arm.com, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org 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/ Many thanks, Ionela. Ionela Voinescu (2): cpufreq,arm,arm64: restructure definitions of arch_set_freq_scale() arm: disable frequency invariance for CONFIG_BL_SWITCHER arch/arm/include/asm/topology.h | 4 ++++ arch/arm64/include/asm/topology.h | 1 + drivers/base/arch_topology.c | 4 ++-- drivers/cpufreq/cpufreq.c | 7 ------- include/linux/arch_topology.h | 2 ++ include/linux/cpufreq.h | 11 ++++++++--- 6 files changed, 17 insertions(+), 12 deletions(-) Acked-by: Sudeep Holla (BL_SWITCHER and topology parts)