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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 151EBC433DF for ; Mon, 13 Jul 2020 11:23:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBE07206F0 for ; Mon, 13 Jul 2020 11:23:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729252AbgGMLXe (ORCPT ); Mon, 13 Jul 2020 07:23:34 -0400 Received: from foss.arm.com ([217.140.110.172]:56216 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728714AbgGMLXe (ORCPT ); Mon, 13 Jul 2020 07:23:34 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2EC2831B; Mon, 13 Jul 2020 04:23:33 -0700 (PDT) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9709E3F7D8; Mon, 13 Jul 2020 04:23:31 -0700 (PDT) Date: Mon, 13 Jul 2020 12:23:25 +0100 From: Lorenzo Pieralisi To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Thomas Petazzoni , Andrew Murray , Bjorn Helgaas , Marek =?iso-8859-1?Q?Beh=FAn?= , Remi Pommarel , Tomasz Maciej Nowak , Xogium , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] PCI: aardvark: Don't touch PCIe registers if no card connected Message-ID: <20200713112325.GA25865@e121166-lin.cambridge.arm.com> References: <20200528143141.29956-1-pali@kernel.org> <20200702083036.12230-1-pali@kernel.org> <20200709113509.GB19638@e121166-lin.cambridge.arm.com> <20200709122208.rmfeuu6zgbwh3fr5@pali> <20200709144701.GA21760@e121166-lin.cambridge.arm.com> <20200709150959.wq6zfkcy4m6hvvpl@pali> <20200710091800.GA3419@e121166-lin.cambridge.arm.com> <20200713082747.e3q3ml3wpbszn4j7@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200713082747.e3q3ml3wpbszn4j7@pali> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Jul 13, 2020 at 10:27:47AM +0200, Pali Rohár wrote: > On Friday 10 July 2020 10:18:00 Lorenzo Pieralisi wrote: > > On Thu, Jul 09, 2020 at 05:09:59PM +0200, Pali Rohár wrote: > > > > I understand that but the bridge bus resource can be trimmed to just > > > > contain the root bus because that's the only one where there is a > > > > chance you can enumerate a device. > > > > > > It is possible to register only root bridge without endpoint? > > > > It is possible to register the root bridge with a trimmed IORESOURCE_BUS > > so that you don't enumerate anything other than the root port. > > Hello Lorenzo! I really do not know how to achieve it. From code it > looks like that pci/probe.c scans child buses unconditionally. > > pci-aardvark.c calls pci_host_probe() which calls functions > pci_scan_root_bus_bridge() which calls pci_scan_child_bus() which calls > pci_scan_child_bus_extend() which calls pci_scan_bridge_extend() (bridge > needs to be reconfigured) which then try to probe child bus via > pci_scan_child_bus_extend() because bridge is not card bus. > > In function pci_scan_bridge_extend() I do not see a way how to skip > probing for child buses which would avoid enumerating aardvark root > bridge when PCIe device is not connected. > > dmesg output contains: > > advk-pcie d0070000.pcie: link never came up > advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00 > pci_bus 0000:00: root bus resource [bus 00-ff] This resource can be limited to the root bus number only before calling pci_host_probe() (ie see pci_parse_request_of_pci_ranges() and code in pci_scan_bridge_extend() that programs primary/secondary/subordinate busses) but I think that only papers over the issue, it does not fix it. I will go over the thread again but I suspect I can merge the patch even though I still believe there is work to be done to understand the issue we are facing. Lorenzo > pci_bus 0000:00: root bus resource [mem 0xe8000000-0xe8ffffff] > pci_bus 0000:00: root bus resource [io 0x0000-0xffff] (bus address [0xe9000000-0xe900ffff]) > pci_bus 0000:00: scanning bus > pci 0000:00:00.0: [1b4b:0100] type 01 class 0x060400 > pci 0000:00:00.0: reg 0x38: [mem 0x00000000-0x000007ff pref] > pci_bus 0000:00: fixups for bus > pci 0000:00:00.0: scanning [bus 00-00] behind bridge, pass 0 > pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring > pci 0000:00:00.0: scanning [bus 00-00] behind bridge, pass 1 > pci_bus 0000:01: scanning bus > advk-pcie d0070000.pcie: advk_pcie_valid_device