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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 9A988C67877 for ; Fri, 12 Oct 2018 17:19:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 556982077C for ; Fri, 12 Oct 2018 17:19:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="Y8qYqLgA"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="P9xegNjU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 556982077C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727494AbeJMAwn (ORCPT ); Fri, 12 Oct 2018 20:52:43 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:53492 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726665AbeJMAwn (ORCPT ); Fri, 12 Oct 2018 20:52:43 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 93F7560BF7; Fri, 12 Oct 2018 17:19:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1539364752; bh=edaEc23W8rGKs8EI7g+Hlztitcko5KtbsKzshiA+j5c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Y8qYqLgAAXD1MMOauH4XGj6SzrpizClQeXvrbGdnbchyci6HJSOH+H3CVF5kcyeA0 5gUxr8IZNS6bXMC1tMwN5QA+FRRR20DXgSj+7eddVFqv4VBE0waYYaz8XrS2hs07KM 0r4SisNv+rqXFzog7V3K5oHSvcSuVh/HoLcwXp2c= Received: from localhost (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: ilina@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 2C2CB60A98; Fri, 12 Oct 2018 17:19:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1539364751; bh=edaEc23W8rGKs8EI7g+Hlztitcko5KtbsKzshiA+j5c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=P9xegNjUkWPUY942zvkd3cwp0h7kLTf7EQBBd9Q2/4CnCo9ow89JDx1MVBUoDi+Ci hIwAjEYFs99IvCzaLpDaGuYoaASNhSQD2kA2LrHO5VdHaw2scka5jJjNZZsBrt7lNc z9wpcBr3kLhrahRVzuBwfrAWNxAbauS7YDbXzw/0= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 2C2CB60A98 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=ilina@codeaurora.org Date: Fri, 12 Oct 2018 11:19:10 -0600 From: Lina Iyer To: Sudeep Holla Cc: "Raju P.L.S.S.S.N" , andy.gross@linaro.org, david.brown@linaro.org, rjw@rjwysocki.net, ulf.hansson@linaro.org, khilman@kernel.org, linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org, rnayak@codeaurora.org, bjorn.andersson@linaro.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, sboyd@kernel.org, evgreen@chromium.org, dianders@chromium.org, mka@chromium.org, Lorenzo Pieralisi Subject: Re: [PATCH RFC v1 7/8] drivers: qcom: cpu_pd: Handle cpu hotplug in the domain Message-ID: <20181012171910.GI2371@codeaurora.org> References: <1539206455-29342-8-git-send-email-rplsssn@codeaurora.org> <20181011112013.GC32752@e107155-lin> <20181011160053.GA2371@codeaurora.org> <20181011161927.GC28583@e107155-lin> <20181011165822.GB2371@codeaurora.org> <20181011173733.GA26447@e107155-lin> <20181011210609.GD2371@codeaurora.org> <20181012150429.GH3401@e107155-lin> <20181012160427.GG2371@codeaurora.org> <20181012170040.GA21057@e107155-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20181012170040.GA21057@e107155-lin> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 12 2018 at 11:01 -0600, Sudeep Holla wrote: >On Fri, Oct 12, 2018 at 10:04:27AM -0600, Lina Iyer wrote: >> On Fri, Oct 12 2018 at 09:04 -0600, Sudeep Holla wrote: > >[...] > >Yes all these are fine but with multiple power-domains/cluster, it's >hard to determine the first CPU. You may be able to identify it within >the power domain but not system wide. So this doesn't scale with large >systems(e.g. 4 - 8 clusters with 16 CPUs). > We would probably not worry too much about power savings in a msec scale, if we have that big a system. The driver is a platform specific driver, primarily intended for a mobile class CPU and usage. In fact, we haven't done this for QC's server class CPUs. >> > I think we are mixing the system sleep states with CPU idle here. >> > If it's system sleeps states, the we need to deal it in some system ops >> > when it's the last CPU in the system and not the cluster/power domain. >> > >> I think the confusion for you is system sleep vs suspend. System sleep >> here (probably more of a QC terminology), refers to powering down the >> entire SoC for very small durations, while not actually suspended. The >> drivers are unaware that this is happening. No hotplug happens and the >> interrupts are not migrated during system sleep. When all the CPUs go >> into cpuidle, the system sleep state is activated and the resource >> requirements are lowered. The resources are brought back to their >> previous active values before we exit cpuidle on any CPU. The drivers >> have no idea that this happened. We have been doing this on QCOM SoCs >> for a decade, so this is not something new for this SoC. Every QCOM SoC >> has been doing this, albeit differently because of their architecture. >> The newer ones do most of these transitions in hardware as opposed to an >> remote CPU. But this is the first time, we are upstreaming this :) >> > >Indeed, I know mobile platforms do such optimisations and I agree it may >save power. As I mentioned above it doesn't scale well with large systems >and also even with single power domains having multiple idle states where >only one state can do this system level idle but not all. As I mentioned >in the other email to Ulf, it's had to generalise this even with DT. >So it's better to have this dealt transparently in the firmware. > Good, then we are on agreement here. But this is how this platform is. It cannot be done in firmware and what we doing here is a Linux platform driver that cleans up nicely without having to piggy back on an external dependency. Thanks, Lina