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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 95AA1C43461 for ; Thu, 10 Sep 2020 12:56:32 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 2E6B5206D4 for ; Thu, 10 Sep 2020 12:56:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="iORvLlXl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E6B5206D4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=SI/NaObDqcflnKoJgGPptU2a55CTVVY/j4tQf93KJZY=; b=iORvLlXlpim417j3PW5e+R6D2 mcFRKpyJifnN3GasvZNHfvjnkYfm9R2KD25/ZEK9GIT1CU9QpyLsNDEDcNyAtWX/eu/ftRD2dhpyE LDxEzDTlX5QZhsCfLG1QEjZtMSv02Vk/ylLkqm+XBbZeIrriD678kRWmrdFdpJPgloVegOZ76h8Kw TMp07Ygsj1ieOhFpEXwSYe6uXFyhi8StWmziBSH/pI+ov6JvDud74PrBW8zH+9S9nu3L7RSJtD8mt Mx1uREAnyJaKJ1QvCk+tvMePQSHKUQRVTUAZSzyeE+P11SN6uTb25EuR72cIpEo+W9XxTPx9PtC5O GZ2U6e55A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kGM6f-0007rb-FD; Thu, 10 Sep 2020 12:55:17 +0000 Received: from cloudserver094114.home.pl ([79.96.170.134]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kGM6b-0007qm-T4; Thu, 10 Sep 2020 12:55:14 +0000 Received: from 89-64-87-170.dynamic.chello.pl (89.64.87.170) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.468) id 0b9e2c09bd0fb81d; Thu, 10 Sep 2020 14:55:07 +0200 From: "Rafael J. Wysocki" To: "Claude. Yen" Subject: Re: [PATCH] PM: s2idle: Introduce syscore callbacks in s2idle flow Date: Thu, 10 Sep 2020 14:55:06 +0200 Message-ID: <1955367.r5QahNuf3v@kreacher> In-Reply-To: <1599099247.4435.4.camel@mtksdccf07> References: <1598943859-21857-1-git-send-email-claude.yen@mediatek.com> <1599099247.4435.4.camel@mtksdccf07> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200910_085514_057868_BC17F029 X-CRM114-Status: GOOD ( 25.52 ) 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: wsd_upstream , "Rafael J. Wysocki" , Frederic Weisbecker , Linux PM , Daniel Lezcano , Douglas Anderson , Bjorn Andersson , "moderated list:ARM/Mediatek SoC..." , Linux ARM , Greg Kroah-Hartman , Matthias Brugger , Thomas Gleixner , Stephen Boyd , Ingo Molnar , Linux Kernel Mailing List Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thursday, September 3, 2020 4:14:07 AM CEST Claude. Yen wrote: > On Tue, 2020-09-01 at 13:57 +0200, Rafael J. Wysocki wrote: > > On Tue, Sep 1, 2020 at 9:05 AM Claude Yen wrote: > > > > > > This series based on 5.9-rc1 > > > This patch makes s2idle call existing syscore callbacks. Currently, > > > when s2idle is selected as system suspend method, callbacks hooked > > > by register_syscore_ops() will not be triggered. This may induce > > > unexpected results. > > > > They are not executed by design. > > > > > For example, sched_clock_suspend() was added to s2idle flow in > > > commit 3f2552f7e9c5 ("timers/sched_clock: Prevent generic sched_clock > > > wrap caused by tick_freeze()") to fix clock wrap problem. However, > > > sched_clock_suspend() is originally registered in syscore callback. > > > > I'm not sure why this matters here. > > If functions in syscore callbacks are needed in s2idle, explicit > migration is needed like commit 3f2552f7e9c5 ("timers/sched_clock: > Prevent generic sched_clock wrap caused by tick_freeze()"). > Thus, I am wondering if such effort could be saved. Yes, it could. You can define platform ops for s2idle and invoke what's needed from there. > > > With this patch, if another syscore callback is needed in s2idle, > > > additional migration effort could be saved. > > > > s2idle cannot execute syscore callbacks, because it doesn' take > > non-boot CPUs offline and it won't do that. > > > > Thanks! > > Yes, the current design of syscore callback needs non-boot CPUs offline. > Considering the following case: in s2idle flow, there is a status that > only one CPU is alive and other CPUs have enter deepest idle state. > This situation is similar to getting non-boot CPUs offline, though all > CPUs are online from kernel's perspective. It is only similar AFAICS. You don't migrate interrupts during s2idle, for example. > Reply from Stephen mentioned that if an operation is needed in both > S2R and s2idle, CPU_PM notifier can be utilized. > In my opinion, CPU_PM notifier is particularly for CPU entering idle > state. In contrast, syscore callback is for system going low power > state. There exists semantic difference between these two callbacks. Fair enough. > Could the current design of syscore callback be re-designed as > system-wide suspend callback? No, it couldn't. > Proposed suspend flow in this patch: > > Freeze tasks > | > V > Device suspend callbacks > | > |-------------s2idle---------- > | | > V | > Disable nonboot CPUs Is this CPU last core to enter idle? > | | > V |------------- > syscore callbacks | | > | No Yes > V | | > platform suspend V V > enter idle syscore callback > | > V > enter idle > The primary problem with this is that on some architectures (x86 at least) the syscore things cannot be run during the s2idle flow. Also there is a way to invoke them through the platform ops as I said. Thanks! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel