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=-5.5 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,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_SANE_2 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 E29ECC433E7 for ; Thu, 3 Sep 2020 02:16:28 +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 B30C620773 for ; Thu, 3 Sep 2020 02:16:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="hzxwYu5E"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b="EZ1kaKjO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B30C620773 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=mediatek.com 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:Date:To:From: Subject:Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=9zSph77hyg0pes741GEGqNCEcsHGJ7W3SjePS2TReLc=; b=hzxwYu5E4Ktd2lR5vnJuB4E99 5Ty7tvtM9lY1BIn2x7/Ee0/edPRbWOkEL6OEHoQbHUB/Cmgc3f8m3A/yQHk6jyREw3G8EqE6nZMIL 1T2r/CtPDruSAjKYDM+LZpk9Tki2p7L1nY7POCr7G77FniQ3nYgJ7eIyfnldVLSIPhkhQYecMeNo/ 7f04BEuNeSTfqR/htzkvqjC+DtbRMWhHJeGIT8FhZNK3w52320IQB4rBrsLk+PZOaToaUZiv8RBqG NmV7aSF2vaMt31P1x8cPu/QfVBOwxVUvQL4OSOgmkAVZJ0pD5owNSKrWw89o4BJSlu2ul1zKoCsQy cOBCLVf7Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDelh-0008RS-Lx; Thu, 03 Sep 2020 02:14:29 +0000 Received: from mailgw02.mediatek.com ([216.200.240.185]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDelb-0008Pq-VU; Thu, 03 Sep 2020 02:14:26 +0000 X-UUID: 68dc97f0ca474a7aaf850b66d612bb0e-20200902 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Transfer-Encoding:MIME-Version:Content-Type:References:In-Reply-To:Date:CC:To:From:Subject:Message-ID; bh=AajrTFn3Auk2rKVdZkKi5kCzYDhKTsT5vsI2D4hD++Q=; b=EZ1kaKjOaJXCgq9CSc/GJa0d6scGXUi12iacVmetb4oWXI5LQeIxFP3dv+kDGi+NRLBuXadjY9QM1DuSqHqlLmWx6hMW4wWAB1biiv1r3eH1IPb3XxAUg8y8Pp/d5QpOtIDaQIPAEiGeH+LQ+WuYL4qGeiE75HHVtFyzEcFd6qA=; X-UUID: 68dc97f0ca474a7aaf850b66d612bb0e-20200902 Received: from mtkcas66.mediatek.inc [(172.29.193.44)] by mailgw02.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 184725020; Wed, 02 Sep 2020 18:14:10 -0800 Received: from MTKMBS01N2.mediatek.inc (172.21.101.79) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 2 Sep 2020 19:14:09 -0700 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs01n2.mediatek.inc (172.21.101.79) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 3 Sep 2020 10:14:06 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Thu, 3 Sep 2020 10:14:06 +0800 Message-ID: <1599099247.4435.4.camel@mtksdccf07> Subject: Re: [PATCH] PM: s2idle: Introduce syscore callbacks in s2idle flow From: Claude.Yen To: "Rafael J. Wysocki" Date: Thu, 3 Sep 2020 10:14:07 +0800 In-Reply-To: References: <1598943859-21857-1-git-send-email-claude.yen@mediatek.com> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-TM-SNTS-SMTP: 1BF4C1899FB0BB2C5EFD5FF48193355333B30A741024572127D6DC6D18D88B412000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200902_221424_201672_BA85A603 X-CRM114-Status: GOOD ( 21.35 ) 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 , Linux PM , Frederic Weisbecker , Daniel Lezcano , "Rafael J. Wysocki" , 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 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. > > 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. 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. Could the current design of syscore callback be re-designed as system-wide suspend callback? 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 Regards, Claude _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel