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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95372C001DB for ; Fri, 4 Aug 2023 04:30:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232118AbjHDEab (ORCPT ); Fri, 4 Aug 2023 00:30:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34160 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbjHDEaa (ORCPT ); Fri, 4 Aug 2023 00:30:30 -0400 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D6C6335BE; Thu, 3 Aug 2023 21:30:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1691123429; x=1722659429; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=7SU+OnhENlKD0/sf+9S44cv0vNFtLHvqcGpWrAJLLlM=; b=YX52LJlEcEFVvEMKj51u64xFMxabYMABhzQ20OsMTRx42XdIqbPOs9EU iddJN2FoUElT+ntd30nRAODs0zIZVLFiaA571rEidsaAsCOJo2TZ1thzl cx+OpxbobD/mRr0LM3EwznzkYjYy+IYo0z8o8qSYI3OGApBAMcZT6z89q ApdthwVnKLSAbtoGtFYkfpq3q9aM3uX0bU0kYec621SwRAXWJKguf/fp7 9sBf9kH52KIAQjM/KkSaQBlTe4CX8fPHeP3Yvy1/N2yW2wU/mDNMaMi9t eHJ1STCry+LvlbKo19J7b/dGs6v+tbZAMUb4mznmanq9Ib2CAgOEAhsIs w==; X-IronPort-AV: E=McAfee;i="6600,9927,10791"; a="401017267" X-IronPort-AV: E=Sophos;i="6.01,254,1684825200"; d="scan'208";a="401017267" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Aug 2023 21:30:29 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10791"; a="853565264" X-IronPort-AV: E=Sophos;i="6.01,254,1684825200"; d="scan'208";a="853565264" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga004.jf.intel.com with ESMTP; 03 Aug 2023 21:30:26 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1qRmSH-009c7u-0F; Fri, 04 Aug 2023 07:30:25 +0300 Date: Fri, 4 Aug 2023 07:30:24 +0300 From: Andy Shevchenko To: Mario Limonciello Cc: "Rafael J . Wysocki" , Mika Westerberg , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Kuppuswamy Sathyanarayanan , Iain Lane , Shyam-sundar S-k Subject: Re: [PATCH v9 3/3] PCI/ACPI: Use device constraints to decide PCI target state fallback policy Message-ID: References: <20230804010229.3664-1-mario.limonciello@amd.com> <20230804010229.3664-4-mario.limonciello@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230804010229.3664-4-mario.limonciello@amd.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Thu, Aug 03, 2023 at 08:02:29PM -0500, Mario Limonciello wrote: > Since commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend") > PCIe ports from modern machines (>=2015) are allowed to be put into D3 by > storing a value to the `bridge_d3` variable in the `struct pci_dev` > structure. > > pci_power_manageable() uses this variable to indicate a PCIe port can > enter D3. > pci_pm_suspend_noirq() uses the return from pci_power_manageable() to > decide whether to try to put a device into its target state for a sleep > cycle via pci_prepare_to_sleep(). > > For devices that support D3, the target state is selected by this policy: > 1. If platform_pci_power_manageable(): > Use platform_pci_choose_state() > 2. If the device is armed for wakeup: > Select the deepest D-state that supports a PME. > 3. Else: > Use D3hot. > > Devices are considered power manageable by the platform when they have > one or more objects described in the table in section 7.3 of the ACPI 6.5 > specification. > > When devices are not considered power manageable; specs are ambiguous as > to what should happen. In this situation Windows 11 leaves PCIe > ports in D0 while Linux puts them into D3 due to the above mentioned > commit. > > In Windows systems that support Modern Standby specify hardware > pre-conditions for the SoC to achieve the lowest power state by device > constraints in a SOC specific "Power Engine Plugin" (PEP) [2] [3]. > They can be marked as disabled or enabled and when enabled can specify > the minimum power state required for an ACPI device. > > When it is ambiguous what should happen, adjust the logic for > pci_target_state() to check whether a device constraint is present > and enabled. > * If power manageable by ACPI use this to get to select target state > * If a device constraint is present but disabled then choose D0 > * If a device constraint is present and enabled then use it > * If a device constraint is not present, then continue to existing > logic (if marked for wakeup use deepest state that PME works) > * If not marked for wakeup choose D3hot ... > +/** > + * acpi_get_lps0_constraint - get any LPS0 constraint for a device > + * @dev: device to get constraint for > + * > + * If a constraint has been specified in the _DSM method for the device, > + * and the constraint is enabled return it. If the constraint is disabled, > + * return 0. Otherwise, return -ENODEV. > + */ I believe you get a kernel-doc warning. Always test kernel doc with scripts/kernel-doc -v -none -Wall ...your file... ... > +/** > + * acpi_pci_device_constraint - determine if the platform has a contraint for the device > + * @dev: PCI device to check > + * @result (out): the constraint specified by the platform > + * > + * If the platform has specified a constraint for a device, this function will > + * return 0 and set @result to the constraint. > + * Otherwise, it will return an error code. > + */ Ditto. ... > +int acpi_pci_device_constraint(struct pci_dev *dev, int *result) > +{ > + int constraint; > + > + constraint = acpi_get_lps0_constraint(&dev->dev); > + pci_dbg(dev, "ACPI device constraint: %d\n", constraint); Does it make sense before the below check? Why can we be interested in the _exact_ negative values? (Note that non-printing is already a sign that either we don't call this or have negative constraint.) > + if (constraint < 0) > + return constraint; > + *result = constraint; > + > + return 0; > +} -- With Best Regards, Andy Shevchenko