From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:42952 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423152AbcFMS4v (ORCPT ); Mon, 13 Jun 2016 14:56:51 -0400 Date: Mon, 13 Jun 2016 13:56:48 -0500 From: Bjorn Helgaas To: "Yong, Jonathan" Cc: linux-pci@vger.kernel.org, bhelgaas@google.com Subject: Re: [PATCH v5] PCI: PTM preliminary implementation Message-ID: <20160613185648.GA6901@localhost> References: <1462956446-27361-1-git-send-email-jonathan.yong@intel.com> <1462956446-27361-2-git-send-email-jonathan.yong@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1462956446-27361-2-git-send-email-jonathan.yong@intel.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Wed, May 11, 2016 at 08:47:26AM +0000, Yong, Jonathan wrote: > Simplified Precision Time Measurement driver, activates PTM feature > if a PCIe PTM requester (as per PCI Express 3.1 Base Specification > section 7.32)is found, but not before checking if the rest of the > PCI hierarchy can support it. > > The driver does not take part in facilitating PTM conversations, > neither does it provide any useful services, it is only responsible > for setting up the required configuration space bits. I'm not convinced we should blindly enable PTM on every device that supports it (especially endpoints), and I think the logic here is more complicated than necessary. I'm going to post a v6 as a draft. My draft is probably not complicated *enough*, but maybe we can figure out some point in the middle. I'm also a little confused about how Root Complex Integrated Endpoints are supposed to use PTM, since they don't have an upstream bridge. Maybe it has to do with an RCRB (Root Complex Register Block, spec r3.1, sec 7.2.3)? I don't think Linux really has any support for that (yet). Bjorn