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 52A53C04EB5 for ; Fri, 7 Feb 2020 14:49:15 +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 2642421741 for ; Fri, 7 Feb 2020 14:49:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="DOxX+ihd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2642421741 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=ZfBhjqLPURHRjRZ05CmkiTfmMFkCR8nMLaThHR6gLQg=; b=DOxX+ihdSi6Fcu +y9tAFEek1PBsT1D5HededjY7u8+IQKAdzAkCs0oW8t4uESHG7dIg4FAxL/zfSdIAopdBWBk9vNFV wG88Gm9RQBGjMYf7p1TMj5Zdy44Frpo+yu2tOEzqaxoXqYe66SN/l2F8d/2Q9FDEwEinEM6F4cJBY mLsvPNy7ax0itlqYDzUp1R+5vK7pvZdaFJX23vu1xUVI+trsm8wd2sOn+OkSo0yc7KJ93L8pkGoHe RIs39ZdgdRQBQExX8HTgmB+28VMKsnWf+07AQtKyRHQH06Xqo+2WVBERH/VZnD3YyhexOUPA1Gyq9 AskumjUzHkKI9SIcWSUg==; 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 1j04wL-0003s3-6v; Fri, 07 Feb 2020 14:49:05 +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 1j04wI-0003rI-Pg for linux-arm-kernel@lists.infradead.org; Fri, 07 Feb 2020 14:49:04 +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 637CA328; Fri, 7 Feb 2020 06:48:58 -0800 (PST) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 330BD3F6CF; Fri, 7 Feb 2020 06:48:56 -0800 (PST) Date: Fri, 7 Feb 2020 14:48:50 +0000 From: Lorenzo Pieralisi To: Ulf Hansson Subject: Re: [PATCH v3 5/7] drivers: firmware: psci: Add hierarchical domain idle states converter Message-ID: <20200207144850.GA18655@e121166-lin.cambridge.arm.com> References: <0d7f7ade-3a1e-5428-d851-f1a886f58712@codeaurora.org> <20200204152132.GA44858@bogus> <6ff7c82d-4204-a339-4070-0154ab4515f1@codeaurora.org> <20200205140603.GB38466@bogus> <20200205161816.GD38466@bogus> <20200206204514.GB8107@codeaurora.org> <20200207111955.GA40103@bogus> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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-20200207_064902_921153_090A41A4 X-CRM114-Status: GOOD ( 20.96 ) 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: Maulik Shah , lsrao@codeaurora.org, Doug Anderson , Rajendra Nayak , Linux PM , linux-arm-msm , "Rafael J. Wysocki" , Linux Kernel Mailing List , Lina Iyer , Stephen Boyd , David Brown , Andy Gross , Evan Green , Sudeep Holla , Bjorn Andersson , Linux ARM 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 Fri, Feb 07, 2020 at 01:32:28PM +0100, Ulf Hansson wrote: > [...] > > > > I understand the arguments for using PC vs OSI and agree with it. But > > > what in PSCI is against Linux knowing when the last core is powering > > > down when the PSCI is configured to do only Platform Cordinated. > > > > Nothing :D. But knowing the evolution and reasons for adding OSI in the > > PSCI specification and having argued about benefits of OSI over PC for > > years and finally when we have it in mainline, this argument of using > > PC for exact reasons why OSI evolved is something I can't understand > > and I am confused. > > > > > There should not be any objection to drivers knowing when all the cores > > > are powered down, be it reference counting CPU PM notifications or using > > > a cleaner approach like this where GendPD framwork does everything > > > cleanly and gives a nice callback. ARM architecture allows for different > > > aspects of CPU access be handled at different levels. I see this as an > > > extension of that approach. > > > > > > > One thing that was repeatedly pointed out during OSI patch review was no > > extra overhead for PC mode where firmware can make decisions. So, just > > use OSI now and let us be done with this discussion of OSI vs PC. If PC > > is what you think you need for future, we can revert all OSI changes and > > start discussing again :-) > > Just to make it clear, I fully agree with you in regards to overhead > for PC-mode. This is especially critical for ARM SoCs with lots of > cores, I assume. > > However, the overhead you refer to, is *only* going to be present in > case when the DTS has the hierarchical CPU topology description with > "power-domains". Because, that is *optional* to use, I am expecting > only those SoC/platforms that needs to manage last-man activities to > use this layout, the others will remain unaffected. In PC mode not only there is no need but it is wrong to manage any last-man activity in the kernel. I wonder why we are still talking about this to be honest. Code to handle PSCI platform coordinated mode has been/is in the kernel today and that's all is needed according to the PSCI specifications. Thanks, Lorenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel