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=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 565D4C352A2 for ; Fri, 7 Feb 2020 11:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33E832253D for ; Fri, 7 Feb 2020 11:25:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726867AbgBGLZO (ORCPT ); Fri, 7 Feb 2020 06:25:14 -0500 Received: from foss.arm.com ([217.140.110.172]:39180 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726674AbgBGLZO (ORCPT ); Fri, 7 Feb 2020 06:25:14 -0500 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 2CC09328; Fri, 7 Feb 2020 03:25:13 -0800 (PST) Received: from bogus (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1627D3F68E; Fri, 7 Feb 2020 03:25:10 -0800 (PST) Date: Fri, 7 Feb 2020 11:25:09 +0000 From: Sudeep Holla To: Bjorn Andersson Cc: Maulik Shah , swboyd@chromium.org, agross@kernel.org, david.brown@linaro.org, Lorenzo.Pieralisi@arm.com, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, evgreen@chromium.org, dianders@chromium.org, rnayak@codeaurora.org, ilina@codeaurora.org, lsrao@codeaurora.org, ulf.hansson@linaro.org, rjw@rjwysocki.net Subject: Re: [PATCH v3 5/7] drivers: firmware: psci: Add hierarchical domain idle states converter Message-ID: <20200207112508.GB40103@bogus> References: <1580736940-6985-1-git-send-email-mkshah@codeaurora.org> <1580736940-6985-6-git-send-email-mkshah@codeaurora.org> <20200203170832.GA38466@bogus> <0d7f7ade-3a1e-5428-d851-f1a886f58712@codeaurora.org> <20200204152132.GA44858@bogus> <6ff7c82d-4204-a339-4070-0154ab4515f1@codeaurora.org> <20200205140603.GB38466@bogus> <20200206211133.GR2514@yoga> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200206211133.GR2514@yoga> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Thu, Feb 06, 2020 at 01:11:33PM -0800, Bjorn Andersson wrote: > On Wed 05 Feb 06:06 PST 2020, Sudeep Holla wrote: > > > On Wed, Feb 05, 2020 at 05:53:00PM +0530, Maulik Shah wrote: > > > > > > On 2/4/2020 8:51 PM, Sudeep Holla wrote: > > > > On Tue, Feb 04, 2020 at 10:22:42AM +0530, Maulik Shah wrote: > > > > > On 2/3/2020 10:38 PM, Sudeep Holla wrote: > > > > > > On Mon, Feb 03, 2020 at 07:05:38PM +0530, Maulik Shah wrote: > > > > > > > From: Ulf Hansson > > > > > > > > > > > > > > If the hierarchical CPU topology is used, but the OS initiated mode isn't > > > > > > > supported, we need to rely solely on the regular cpuidle framework to > > > > > > > manage the idle state selection, rather than using genpd and its > > > > > > > governor. > > > > > > > > > > > > > > For this reason, introduce a new PSCI DT helper function, > > > > > > > psci_dt_pm_domains_parse_states(), which parses and converts the > > > > > > > hierarchically described domain idle states from DT, into regular flattened > > > > > > > cpuidle states. The converted states are added to the existing cpuidle > > > > > > > driver's array of idle states, which make them available for cpuidle. > > > > > > > > > > > > > And what's the main motivation for this if OSI is not supported in the > > > > > > firmware ? > > > > > Hi Sudeep, > > > > > > > > > > Main motivation is to do last-man activities before the CPU cluster can > > > > > enter a deep idle state. > > > > > > > > > Details on those last-man activities will help the discussion. Basically > > > > I am wondering what they are and why they need to done in OSPM ? > > > > > > Hi Sudeep, > > > > > > there are cases like, > > > > > > Last cpu going to deepest idle mode need to lower various resoruce > > > requirements (for eg DDR freq). > > > > > > > In PC mode, only PSCI implementation knows the last man and there shouldn't > > be any notion of it in OS. If you need it, you may need OSI. You are still > > mixing up the things. NACK for any such approach, sorry. > > > > Forgive me if I'm misunderstanding PSCI's role here, but doesn't it deal > with the power management of the "processor subsystem" in the SoC? > Yes. > In the Qualcomm platforms most resources (voltage rails, clocks, etc) > are controlled through a power controller that provides controls for a > state when the CPU subsystem is running and when it's asleep. This > allows non-CPU-related device to control if resources that are shared > with the CPU subsystem should be kept on when the last CPU/cluster goes > down. > I understand that. > An example of this would be the display controller voting to keep a > voltage rail on after the CPU subsystem collapses, because the display > is still on. > OK > But as long as the CPU subsystem is running it will keep these resources > available and there's no need to change these votes (e.g. if the display > is turned on and off while the CPU is active the sleep-requests cancels > out), so they are simply cached/batched up in the RPMh driver and what > Maulik's series is attempting to do is to flush the cached values when > Linux believes that the firmware might decide to enter a lower power > state. > I understand all these. What I am arguing is that in PC mode, PSCI firmware is the one who needs to vote and not OSPM because it is responsible for pulling the plugs off the CPU/Cluster. So lets us not bring that to OSPM. OSI was invented to do all such crazy things in OSPM, please feel free to play with that ;-) -- Regards, Sudeep