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, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 53DCCC433B4 for ; Wed, 28 Apr 2021 18:12:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1693D61412 for ; Wed, 28 Apr 2021 18:12:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243581AbhD1SM5 (ORCPT ); Wed, 28 Apr 2021 14:12:57 -0400 Received: from 8bytes.org ([81.169.241.247]:36574 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240210AbhD1SM5 (ORCPT ); Wed, 28 Apr 2021 14:12:57 -0400 Received: by theia.8bytes.org (Postfix, from userid 1000) id 32FF9366; Wed, 28 Apr 2021 20:12:11 +0200 (CEST) Date: Wed, 28 Apr 2021 20:12:07 +0200 From: Joerg Roedel To: "Kuppuswamy, Sathyanarayanan" Cc: Bjorn Helgaas , rjw@rjwysocki.net, Len Brown , linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Joerg Roedel Subject: Re: [RFC PATCH] PCI/APCI: Move acpi_pci_osc_support() check to negotiation phase Message-ID: References: <20210428081857.10322-1-joro@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Wed, Apr 28, 2021 at 10:21:12AM -0700, Kuppuswamy, Sathyanarayanan wrote: > > > On 4/28/21 1:18 AM, Joerg Roedel wrote: > > From: Joerg Roedel > > > > The acpi_pci_osc_support() does an _OSC query with _OSC supported set > > to what the OS supports but a zero _OSC control value. This is > > problematic on some platforms where the firmware allows to configure > > whether DPC is under OS or Firmware control. > > Do we run acpi_pci_osc_support() only to check whether _OSC is > supported ? Or does it serve any other purpose. I am not 100% sure, but to me it looks like the pure purpose of the acpi_pci_osc_support() call was indeed to check whether the firmware is willing to grant the OS control over some PCIe features. > > When DPC is configured to be under OS control these platforms will > > issue a warning in the firmware log that the OS does not support DPC. > > Also, is there any other benefit from this patch other than fixing > a warning message in firmware? Not much other benefit, besides some removed code. But those messages can confuse the system owner and are worth getting rid of imho. Regards, Joerg