From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755271AbeD3VDD (ORCPT ); Mon, 30 Apr 2018 17:03:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:48172 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755162AbeD3VC7 (ORCPT ); Mon, 30 Apr 2018 17:02:59 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5246122B37 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=helgaas@kernel.org Date: Mon, 30 Apr 2018 16:02:56 -0500 From: Bjorn Helgaas To: linux-pci@vger.kernel.org Cc: "Rafael J. Wysocki" , Sinan Kaya , Rajat Jain , Srinath Mannam , Ray Jui , Keith Busch , linux-acpi@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 0/2] PCI/ASPM: Tighten up ASPM L1.2 and LTR usage Message-ID: <20180430210256.GE95643@bhelgaas-glaptop.roam.corp.google.com> References: <152417080402.76853.4258398181136860884.stgit@bhelgaas-glaptop.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <152417080402.76853.4258398181136860884.stgit@bhelgaas-glaptop.roam.corp.google.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 19, 2018 at 04:05:19PM -0500, Bjorn Helgaas wrote: > The ASPM L1.2 substate depends on LTR information. Per the PCI > Firmware spec, the OS is supposed to negotiate with the platform for > control of the LTR feature, but previously we didn't do that. > > In addition, we must not enable LTR in an endpoint unless the Root > Complex and all intermediate switches also support LTR. We already > took care of that in pci_configure_ltr(), but we didn't ensure that > LTR was enabled before allowing ASPM L1.2 to be enabled. > > These patches fix both of these issues. Or rather, they *should* fix > them. I don't have hardware to test them, so any help with testing > would be appreciated. > > I think the most likely issue would be a platform where the hardware > supports LTR and the ASPM L1.2 substate, but the BIOS doesn't support > LTR in _OSC. In that case, we previously could have enabled ASPM L1.2 > (though it probably wouldn't work correctly), and after these patches, > we should not enable ASPM L1.2. > > You can look for issues by comparing dmesg and "lspci -vv" output > before and after these patches. > > It would also be interesting to collect an acpidump from platforms > that support LTR, even if there's no endpoint that supports ASPM L1.2. > The acpidump should show that _OSC supports LTR. > > I included some NVMe folks because these were motivated by Srinath's > recent report of LTR and ASPM issues with a Samsung NVMe SSD > Controller SM961/PM961 device, so this is sort of FYI in case you see > similar issues or are in a position to test these. > > --- > > Bjorn Helgaas (2): > PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR > PCI/ACPI: Request LTR control from platform before using it > > > drivers/acpi/pci_root.c | 7 +++++++ > drivers/pci/pcie/aspm.c | 9 +++++++++ > drivers/pci/probe.c | 5 +++++ > include/linux/acpi.h | 3 ++- > include/linux/pci.h | 1 + > 5 files changed, 24 insertions(+), 1 deletion(-) Applied to pci/aspm for v4.18 with Rafael's reviewed-by and Srinath's tested-by (on first patch).