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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 A74EBC10F00 for ; Fri, 6 Mar 2020 10:04:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 874672072D for ; Fri, 6 Mar 2020 10:04:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726079AbgCFKEl (ORCPT ); Fri, 6 Mar 2020 05:04:41 -0500 Received: from foss.arm.com ([217.140.110.172]:58854 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbgCFKEl (ORCPT ); Fri, 6 Mar 2020 05:04:41 -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 5298C31B; Fri, 6 Mar 2020 02:04:40 -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 C16CB3F6C4; Fri, 6 Mar 2020 02:04:38 -0800 (PST) Date: Fri, 6 Mar 2020 10:04:31 +0000 From: Sudeep Holla To: Ulf Hansson Cc: Lorenzo Pieralisi , Linux PM , "Rafael J . Wysocki" , Daniel Lezcano , Lina Iyer , Vincent Guittot , Stephen Boyd , Bjorn Andersson , Benjamin Gaignard , Sudeep Holla , Linux ARM Subject: Re: [PATCH v2 4/4] cpuidle: psci: Allow WFI to be the only state for the hierarchical topology Message-ID: <20200306100431.GA16541@bogus> References: <20200303203559.23995-1-ulf.hansson@linaro.org> <20200303203559.23995-5-ulf.hansson@linaro.org> <20200304122312.GE25004@bogus> <20200305162321.GB53631@bogus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Fri, Mar 06, 2020 at 10:28:10AM +0100, Ulf Hansson wrote: > On Thu, 5 Mar 2020 at 17:23, Sudeep Holla wrote: > > [...] > > OK. The only state that cluster can enter when CPUs are in WFI are > > cluster WFI and most hardware can handle it automatically. I don't see > > the need to do any extra work for that. > > This isn't about cluster WFI, but about deeper cluster states, such as > a cluster-clock-gated-state and a cluster-power-off-state. It's an ST > platform, which Benjamin is working on. > Then definitely something is completely wrong. You can't enter deeper cluster states(clock-gated and power-off to be specific) with CPU in just WFI state. So, if the attempt here is to enter those states, I disagree with the change. Benjamin, please share the complete hierarchical topology for your platform. > > > > > Then, after we have called pm_runtime_put_sync_suspend() a few lines > > > above, we may potentially have a "domain state" to use, instead of the > > > WFI state. > > > > > > > Are they any platforms with this potential "domain state" to use with > > CPU WFI. I want to understand this better. > > > > > In this case, if we would have called psci_enter_state(), that would > > > lead us to calling cpu_do_idle() from the __CPU_PM_CPU_IDLE_ENTER() > > > macro, becuase idx is zero. In other words, the domain state would > > > become unused. > > > > > > > For a domain state to become unused with WFI, it needs to be available > > and I am not 100% sure of that. > > With these changes from the series, we can fully conform to the > hierarchical DT bindings for PSCI. > Theoretically may be, but may not confirm to the hardware states. > I am not sure I understand your concern, is there a cost involved by > applying this? > Yes as mentioned above. -- Regards, Sudeep