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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BC555D39011 for ; Wed, 14 Jan 2026 20:19:44 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6765C10E243; Wed, 14 Jan 2026 20:19:44 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="atTc3oxy"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9056310E243 for ; Wed, 14 Jan 2026 20:19:43 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 574DB40885; Wed, 14 Jan 2026 20:19:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16176C4CEF7; Wed, 14 Jan 2026 20:19:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768421983; bh=3bBRNO/DZD2q8tmTYU6yb/d4RB4rCHU+aLQ/hYtUSeY=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=atTc3oxygJsuydlLq+jkyB4ynUI8H2lfS1q2dU2ih5Xikv1kWI1C/QWlX8Qg2yApn OjCL4RxUnGjLydjOj9NB34JzPETh120lf0ea6kCtYD1c4dk9EuNc5e+3OJoLMK1lhb Fn1iaos/BzuAqxl6kn8ZTTza45H+g07CD3HATVgnjziwE9sx4UFxvJ/Nd1cf6xuzeZ MgDGRi1yUSC0kPJSV+FPY+g9a5RY1er6fy0xCKZJm3ftgJFRPluDcP8NNfQ8Y8IR+/ F1rDNfiGiRbRyIHigvcCNZfJNmzIDX8krNu1a5SWrbswwHCQzZBwCNMfOCru7Vc44T GoO6P22Vnmd1Q== Date: Wed, 14 Jan 2026 14:19:41 -0600 From: Bjorn Helgaas To: Badal Nilawar Cc: intel-xe@lists.freedesktop.org, linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, anshuman.gupta@intel.com, rafael@kernel.org, lenb@kernel.org, bhelgaas@google.com, ilpo.jarvinen@linux.intel.com, rodrigo.vivi@intel.com, varun.gupta@intel.com, ville.syrjala@linux.intel.com, uma.shankar@intel.com, karthik.poosa@intel.com, matthew.auld@intel.com, sk.anirban@intel.com, raag.jadav@intel.com Subject: Re: [PATCH v6 02/12] PCI/ACPI: Add PERST# Assertion Delay _DSM method Message-ID: <20260114201941.GA832768@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260114195516.GA830795@bhelgaas> X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Wed, Jan 14, 2026 at 01:55:17PM -0600, Bjorn Helgaas wrote: > On Tue, Jan 13, 2026 at 10:12:03PM +0530, Badal Nilawar wrote: > > From: Anshuman Gupta > > > > Implement _DSM Method 0Bh as per PCI Firmware r3.3, sec 4.6.10, to request > > fixed delay in timing between the time the PME_TO_Ack message is received > > at the PCI Express Downstream Port that originated the PME_Turn_Off > > message, and the time the platform asserts PERST# to the slot during the > > corresponding Endpoint’s or PCI Express Upstream Port’s transition to > > D3cold while the system is in an ACPI operational state. > > Host platform supporting this feature ensures that device is observing > > this delay in every applicable D3Cold transition. > ... > Sec 4.6.11 also says we should track this per Downstream Port and > request the maximum of delays requested by any child. So I think we > need to: > > - add a perst_delay in struct pci_dev If you do this, name it "perst_delay_us" so we know the units. > - when we find this _DSM, set > bdev.perst_delay = max(bdev.perst_delay, delay_us) > > - pass bdev.perst_delay to the _DSM instead of delay_us