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=-2.2 required=3.0 tests=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 40FE3C432C0 for ; Wed, 27 Nov 2019 13:32:13 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 09A442071E for ; Wed, 27 Nov 2019 13:32:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="XlQCYrRE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 09A442071E 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+infradead-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=bombadil.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=Mi+r/mPNYWcwPupxfjftUZT70vAMX5KkSuxcFIVt1QQ=; b=XlQCYrREbOrnvY XCXHsWV9fv2fx+Oym9Df+Kz8curQcHp0yBm7lwN+rAtvGwO1zQ9PjAmS+VD66qhc3VpG9rh9JwPwC RUaxcDFlNCV/gLgOmu1nETQzZmHSGj6lod9MELLw6k+mMw9gMMPtVge8MuiXRFrn6E/ND0UR75ZNU nvpdjJoJhBT6pSCY+7Ps7Mo7zjSu+IesLjF5/5Z6AMxiAqap6oNs6aIYICTopWD1z+mMjOcgr4T8Z CZG6kTMfyBn1eCUT0N+R1SSJFxE39F7xDLl1qSrTiJ4cJyGezGmTrSMHLoVcR+I2Ff8T7XSXNB7dK /W//6dpqbYDa9P9fwW7A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iZxQS-000525-5p; Wed, 27 Nov 2019 13:32:12 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iZxQO-00051I-JU for linux-arm-kernel@lists.infradead.org; Wed, 27 Nov 2019 13:32:10 +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 8C58D31B; Wed, 27 Nov 2019 05:32:04 -0800 (PST) Received: from bogus (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1D9A83F52E; Wed, 27 Nov 2019 05:32:03 -0800 (PST) Date: Wed, 27 Nov 2019 13:32:01 +0000 From: Sudeep Holla To: Viresh Kumar Subject: Re: [PATCH] cpufreq: vexpress-spc: Fix wrong alternation of policy->related_cpus during CPU hp Message-ID: <20191127133200.GE29301@bogus> References: <20191127114801.23837-1-dietmar.eggemann@arm.com> <20191127120816.GC29301@bogus> <20191127121402.vd3tul4gmqm6qtyb@vireshk-i7> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191127121402.vd3tul4gmqm6qtyb@vireshk-i7> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191127_053208_686732_6DA1133D X-CRM114-Status: GOOD ( 21.69 ) 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: Lorenzo Pieralisi , linux-pm@vger.kernel.org, "Rafael J . Wysocki" , Liviu Dudau , linux-kernel@vger.kernel.org, Dietmar Eggemann , linux-arm-kernel@lists.infradead.org, Sudeep Holla , Morten Rasmussen , Lukasz Luba Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Nov 27, 2019 at 05:44:02PM +0530, Viresh Kumar wrote: > On 27-11-19, 12:08, Sudeep Holla wrote: > > On Wed, Nov 27, 2019 at 12:48:01PM +0100, Dietmar Eggemann wrote: > > > Since commit ca74b316df96 ("arm: Use common cpu_topology structure and > > > functions.") the core cpumask has to be modified during cpu hotplug > > > operations. > > > > > > ("arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC") > > > [1] fixed that but revealed another issue on TC2, i.e in its cpufreq > > > driver. > > > > > > During CPU hp stress operations on multiple CPUs, policy->related_cpus > > > can be altered. This is wrong since this cpumask should contain the > > > online and offline CPUs. > > > > > > The WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus)) in > > > cpufreq_online() triggers in this case. > > > > > > The core cpumask can't be used to set the policy->cpus in > > > ve_spc_cpufreq_init() anymore in case it is called via > > > cpuhp_cpufreq_online()->cpufreq_online()->cpufreq_driver->init(). > > > > > > An empty online() callback can be used to avoid that the init() > > > driver function is called during CPU hotplug in so that > > > policy->related_cpus will not be changed. > > > > > > > Unlike DT based drivers, it not easy to get the fixed cpumask unless we > > add some mechanism to extract it based on clks/OPP added. I prefer > > this simple solution instead. > > I will call this a work-around for the problem and not really the > solution, though I won't necessarily oppose it. There are cases which > will break even with this solution. > I agree and that's the reason I spoke out my thought aloud here :) > - Boot board with cpufreq driver as module. > - Offline all CPUs except CPU0. > - insert cpufreq driver. > - online all CPUs. > Indeed, not just boot anytime since it's a module :) > Now there is no guarantee that the last online will get the mask > properly, if I have understood the problem well :) > Yes > But yeah, who does this kind of messy work anyway :) > I won't bet on that ;) > FWIW, we need a proper way (may be from architecture code) to find > list of all CPUs that share clock line. > Yes but there's no architectural way. I need to revise and see tc2_pm.c to check if we can do any magic there. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel