From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751995AbdGGPBW (ORCPT ); Fri, 7 Jul 2017 11:01:22 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:56546 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750726AbdGGPBV (ORCPT ); Fri, 7 Jul 2017 11:01:21 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 7B1E16032D Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=okaya@codeaurora.org Subject: Re: [PATCH V2] PCI: Do not enable extended tags on pre-dated (v1.x) systems To: wim.ten.have@oracle.com Cc: linux-pci@vger.kernel.org, timur@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Bjorn Helgaas , linux-kernel@vger.kernel.org References: <1499439193-16628-1-git-send-email-okaya@codeaurora.org> From: Sinan Kaya Message-ID: <7d6e99b9-bdef-845a-a542-2c47f429eb12@codeaurora.org> Date: Fri, 7 Jul 2017 11:01:16 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <1499439193-16628-1-git-send-email-okaya@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Wim, On 7/7/2017 10:53 AM, Sinan Kaya wrote: > According to extended tags ECN document, all PCIe receivers are expected > to support extended tags support. It should be safe to enable extended > tags on endpoints without checking compatibility. > > This assumption seems to be working fine except for the legacy systems. > The ECN has been written against PCIE spec version 2.0. Therefore, we need > to exclude all version 1.0 devices from this change as there is HW out > there that can't handle extended tags. > > Note that the default value of Extended Tags Enable bit is implementation > specific. Therefore, we are clearing the bit by default when incompatible > HW is found without assuming that value is zero. > > Reported-by: Wim ten Have > Link: https://pcisig.com/sites/default/files/specification_documents/ECN_Extended_Tag_Enable_Default_05Sept2008_final.pdf > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1467674 > Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported") > Signed-off-by: Sinan Kaya > --- Can you also give this a spin? I don't have a system with v1 PCIe bridges. I only tested v2 and later code path. I tried to address Jike Song concerns on this version and removed your tested-by since the code changed. Sinan -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.