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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 CEB1CC5519F for ; Wed, 25 Nov 2020 08:07:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7110720708 for ; Wed, 25 Nov 2020 08:07:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726612AbgKYIHI (ORCPT ); Wed, 25 Nov 2020 03:07:08 -0500 Received: from mga09.intel.com ([134.134.136.24]:65092 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726325AbgKYIHI (ORCPT ); Wed, 25 Nov 2020 03:07:08 -0500 IronPort-SDR: 0LxcttN07aAYUtUiTtigLEC5/gAp+Rnp2NTYdQl4Vw+7WFFTURcle6pL7aauFFPoS89Ve8/vtA 6Tl569TnMDyQ== X-IronPort-AV: E=McAfee;i="6000,8403,9815"; a="172244065" X-IronPort-AV: E=Sophos;i="5.78,368,1599548400"; d="scan'208";a="172244065" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Nov 2020 00:07:05 -0800 IronPort-SDR: i8smOXMHi2IWQtJp5vzRd/iYtOun9bTO172CUBgV17TJhR9iQnXIDS5/Zc/5MhBzDdn62x/UR4 j3oauEfYsRoQ== X-IronPort-AV: E=Sophos;i="5.78,368,1599548400"; d="scan'208";a="332892300" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.163]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Nov 2020 00:07:02 -0800 Received: by lahna (sSMTP sendmail emulation); Wed, 25 Nov 2020 10:06:59 +0200 Date: Wed, 25 Nov 2020 10:06:59 +0200 From: Mika Westerberg To: "Rafael J. Wysocki" Cc: Linux ACPI , LKML , Linux PM , Linux PCI , "Rafael J. Wysocki" , Bjorn Helgaas , Kai-Heng Feng Subject: Re: [PATCH v1 1/2] PM: ACPI: PCI: Drop acpi_pm_set_bridge_wakeup() Message-ID: <20201125080659.GB2532@lahna.fi.intel.com> References: <27714988.CF3CpBaniU@kreacher> <2261308.G18gbxz5ee@kreacher> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2261308.G18gbxz5ee@kreacher> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Nov 24, 2020 at 08:44:00PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > The idea behind acpi_pm_set_bridge_wakeup() was to allow bridges to > be reference counted for wakeup enabling, because they may be enabled > to signal wakeup on behalf of their subordinate devices and that > may happen for multiple times in a row, whereas for the other devices > it only makes sense to enable wakeup signaling once. > > However, this becomes problematic if the bridge itself is suspended, > because it is treated as a "regular" device in that case and the > reference counting doesn't work. > > For instance, suppose that there are two devices below a bridge and > they both can signal wakeup. Every time one of them is suspended, > wakeup signaling is enabled for the bridge, so when they both have > been suspended, the bridge's wakeup reference counter value is 2. > > Say that the bridge is suspended subsequently and acpi_pci_wakeup() > is called for it. Because the bridge can signal wakeup, that > function will invoke acpi_pm_set_device_wakeup() to configure it > and __acpi_pm_set_device_wakeup() will be called with the last > argument equal to 1. This causes __acpi_device_wakeup_enable() > invoked by it to omit the reference counting, because the reference > counter of the target device (the bridge) is 2 at that time. > > Now say that the bridge resumes and one of the device below it > resumes too, so the bridge's reference counter becomes 0 and > wakeup signaling is disabled for it, but there is still the other > suspended device which may need the bridge to signal wakeup on its > behalf and that is not going to work. > > To address this scenario, use wakeup enable reference counting for > all devices, not just for bridges, so drop the last argument from > __acpi_device_wakeup_enable() and __acpi_pm_set_device_wakeup(), > which causes acpi_pm_set_device_wakeup() and > acpi_pm_set_bridge_wakeup() to become identical, so drop the latter > and use the former instead of it everywhere. > > Signed-off-by: Rafael J. Wysocki Reviewed-by: Mika Westerberg