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=-0.8 required=3.0 tests=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 45D70C2D0F0 for ; Tue, 31 Mar 2020 22:34:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1946920842 for ; Tue, 31 Mar 2020 22:34:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731425AbgCaWeX (ORCPT ); Tue, 31 Mar 2020 18:34:23 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:33770 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727955AbgCaWeW (ORCPT ); Tue, 31 Mar 2020 18:34:22 -0400 Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jJPSQ-0000wr-Sx; Wed, 01 Apr 2020 00:34:07 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 5CA2F103A01; Wed, 1 Apr 2020 00:34:06 +0200 (CEST) From: Thomas Gleixner To: Bjorn Helgaas , Dave Jiang Cc: vkoul@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, gregkh@linuxfoundation.org, arnd@arndb.de, linux-kernel@vger.kernel.org, x86@kernel.org, dmaengine@vger.kernel.org, dan.j.williams@intel.com, ashok.raj@intel.com, fenghua.yu@intel.com, linux-pci@vger.kernel.org, tony.luck@intel.com, jing.lin@intel.com, sanjay.k.kumar@intel.com Subject: Re: [PATCH 2/6] device/pci: add cmdmem cap to pci_dev In-Reply-To: <20200331220006.GA37376@google.com> References: <20200331220006.GA37376@google.com> Date: Wed, 01 Apr 2020 00:34:06 +0200 Message-ID: <87ftdoupb5.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bjorn Helgaas writes: > On Tue, Mar 31, 2020 at 10:59:44AM -0700, Dave Jiang wrote: >> On 3/31/2020 9:03 AM, Bjorn Helgaas wrote: >> > On Mon, Mar 30, 2020 at 02:27:00PM -0700, Dave Jiang wrote: >> > > Since the current accelerator devices do not have standard PCIe capability >> > > enumeration for accepting ENQCMDS yet, for now an attribute of pdev->cmdmem has >> > > been added to struct pci_dev. Currently a PCI quirk must be used for the >> > > devices that have such cap until the PCI cap is standardized. Add a helper >> > > function to provide the check if a device supports the cmdmem capability. >> > > >> > > Such capability is expected to be added to PCIe device cap enumeration in >> > > the future. >> > This needs some sort of thumbnail description of what "synchronous >> > write notification" and "cmdmem" mean. >> >> I will add more explanation. >> >> > Do you have a pointer to a PCI-SIG ECR or similar? >> >> Deferrable Memory Write (DMWr) ECR >> >> https://members.pcisig.com/wg/PCI-SIG/document/13747 >> >> From what I'm told it should be available for public review by EOW. > > Please use terminology from the spec instead of things like > "synchronous write notification". > > AIUI, ENQCMDS is an x86 instruction. That would have no meaning in > the PCIe domain. > > I'm not committing to acking any part of this before the ECR is > accepted, but if you're adding support for the feature described by > the ECR, you might as well add support for discovering the DMWr > capability via Device Capabilities 2 as described in the ECR. Don't worry. There is nothing to decide and ack before the basic architecture support for ENQCMD[S] is discussed and accepted. The patches providing this support have been posted 2 hrs before this pile hit the mailing lists yesterday. Thanks, tglx