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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 75839C433E1 for ; Mon, 13 Jul 2020 08:27:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E2252073A for ; Mon, 13 Jul 2020 08:27:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594628871; bh=Mzu5M8J7qSSUdRCwII36kgtNKcgkXpCVKQg6uo3q2aM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=hSCzl6iLSDgwArIGSzhT4MfE4DHTMZBnWTrzhMjzDnySXt0e4iz3FMxpQFvOMABT5 NAOamXWr+OD92vkPEew8i4SLhpalmLwlQ+DszVQxtJ7VSTeE7xaLabBNakYsZSe6Kt rwT41AfZSmy8HeHlrxYMMhM2JoWbf7YCN0qUfnSk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729027AbgGMI1u (ORCPT ); Mon, 13 Jul 2020 04:27:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:59374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725818AbgGMI1u (ORCPT ); Mon, 13 Jul 2020 04:27:50 -0400 Received: from pali.im (pali.im [31.31.79.79]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CA7FD2067D; Mon, 13 Jul 2020 08:27:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594628869; bh=Mzu5M8J7qSSUdRCwII36kgtNKcgkXpCVKQg6uo3q2aM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rBywLjk8q/9SCapOGSwOqN3Vg8NO4eBR99O6xSiKoblZ6EvtQULlpw0SYhMGfq1yX E385iR9JXzbY0Vl5jNNie7Nrv2DcIwUsZzy83qd8i/v9NzvIu/XMa1SdSTJdO13qWo aWbYjZSjZpteIpXWZwv7X29SmxWQNPC2bhh3WKIY= Received: by pali.im (Postfix) id E8996857; Mon, 13 Jul 2020 10:27:47 +0200 (CEST) Date: Mon, 13 Jul 2020 10:27:47 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Lorenzo Pieralisi Cc: Thomas Petazzoni , Andrew Murray , Bjorn Helgaas , Marek =?utf-8?B?QmVow7pu?= , 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: <20200713082747.e3q3ml3wpbszn4j7@pali> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200710091800.GA3419@e121166-lin.cambridge.arm.com> User-Agent: NeoMutt/20180716 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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] 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