From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751651Ab0FVSTN (ORCPT ); Tue, 22 Jun 2010 14:19:13 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:38585 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750930Ab0FVSTM (ORCPT ); Tue, 22 Jun 2010 14:19:12 -0400 From: "Rafael J. Wysocki" To: Matthew Garrett Subject: Re: [PATCH] ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe Date: Tue, 22 Jun 2010 20:17:29 +0200 User-Agent: KMail/1.13.3 (Linux/2.6.35-rc3-rjw+; KDE/4.4.3; x86_64; ; ) Cc: jbarnes@virtuousgeek.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org References: <1277220343-25168-1-git-send-email-mjg@redhat.com> In-Reply-To: <1277220343-25168-1-git-send-email-mjg@redhat.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-2" Content-Transfer-Encoding: 7bit Message-Id: <201006222017.30023.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, June 22, 2010, Matthew Garrett wrote: > The PCI SIG documentation for the _OSC OS/firmware handshaking interface > states: > > "If the _OSC control method is absent from the scope of a host bridge > device, then the operating system must not enable or attempt to use any > features defined in this section for the hierarchy originated by the host > bridge." > > The obvious interpretation of this is that the OS should not attempt to use > PCIe hotplug, PME or AER - however, the specification also notes that an > _OSC method is *required* for PCIe hierarchies, and experimental validation > with An Alternative OS indicates that it doesn't use any PCIe functionality > if the _OSC method is missing. That arguably means we shouldn't be using > MSI or extended config space, but right now our problems seem to be limited > to vendors being surprised when ASPM gets enabled on machines when other > OSs refuse to do so. So, for now, let's just disable ASPM if the _OSC > method doesn't exist or refuses to hand over PCIe capability control. > > Signed-off-by: Matthew Garrett Acked-by: Rafael J. Wysocki > --- > drivers/acpi/pci_root.c | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c > index 1af8081..7167213 100644 > --- a/drivers/acpi/pci_root.c > +++ b/drivers/acpi/pci_root.c > @@ -32,6 +32,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -576,6 +577,14 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device) > if (flags != base_flags) > acpi_pci_osc_support(root, flags); > > + status = acpi_pci_osc_control_set(root->device->handle, > + OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL); > + > + if (ACPI_FAILURE(status)) { > + printk(KERN_INFO "Unable to assume PCIe control: Disabling ASPM\n"); > + pcie_no_aspm(); > + } > + > return 0; > > end: >