From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752617AbbFNPaX (ORCPT ); Sun, 14 Jun 2015 11:30:23 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:40929 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751549AbbFNPaO (ORCPT ); Sun, 14 Jun 2015 11:30:14 -0400 Message-ID: <557D9DF0.50806@roeck-us.net> Date: Sun, 14 Jun 2015 08:29:52 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Lorenzo Pieralisi CC: "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , Ralf Baechle , "James E.J. Bottomley" , Michael Ellerman , Bjorn Helgaas , Richard Henderson , Benjamin Herrenschmidt , David Howells , Russell King , Tony Luck , "David S. Miller" , Ingo Molnar , Michal Simek , Chris Zankel , Arnd Bergmann , Krzysztof Halasa , Phil Edworthy , Jason Gunthorpe , Jingoo Han , Lucas Stach , Simon Horman , Minghuan Lian , Murali Karicheri , Tanmay Inamdar , Kishon Vijay Abraham I , Thierry Reding , Thomas Petazzoni , Will Deacon , Jayachandran C , "suravee.suthikulpanit@amd.com" Subject: Re: [RFC/RFT PATCH v2] PCI: move pci_read_bridge_bases to the generic PCI layer References: <1433840506-20083-1-git-send-email-lorenzo.pieralisi@arm.com> <20150613014755.GA29649@roeck-us.net> <20150613091200.GA8125@red-moon> In-Reply-To: <20150613091200.GA8125@red-moon> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=0.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/13/2015 02:12 AM, Lorenzo Pieralisi wrote: > On Sat, Jun 13, 2015 at 02:47:55AM +0100, Guenter Roeck wrote: >> On Tue, Jun 09, 2015 at 10:01:45AM +0100, Lorenzo Pieralisi wrote: >>> When a PCI bus is scanned, upon PCI bridge detection the kernel >>> has to read the bridge registers to set-up its resources so that >>> the PCI resource hierarchy can be validated properly. >>> >>> Most if not all architectures read PCI bridge registers in the >>> pcibios_fixup_bus hook, that is called by the PCI generic layer >>> whenever a PCI bus is scanned. >>> >>> Since pci_read_bridge_bases is an arch agnostic operation (and it >>> is carried out on all architectures) it can be moved to the generic >>> PCI layer in order to consolidate code and remove the respective >>> calls from the architectures back-ends. >>> >>> The PCI_PROBE_ONLY flag is not checked before calling >>> pci_read_bridge_buses in the generic layer since reading the bridge >>> bases is not related to resources assignment; this implies that it >>> can be carried out safely on PCI_PROBE_ONLY systems too and should >>> not affect architectures (alpha, mips) that check the PCI_PROBE_ONLY >>> flag before reading the bridge bases. >>> >>> In order to validate the resource hierarchy as soon as the resources >>> themselves are probed (ie read from the bridge), this patch also adds >>> code to pci_read_bridge_bases that claims the bridge resources, so that >>> they are validated and inserted in the resource hierarchy as soon as >>> the bridge bases are probed. >>> >> >> Hi Lorenzo, >> >> on one of our systems, I see a lot of messages with your patch applied. >> >> bart kernel: pci 0000:b0:00.0: can't claim BAR 7 [io 0x0000-0x0fff]: no compatible bridge window >> bart kernel: pci 0000:b0:00.0: can't claim BAR 8 [mem 0x94000000-0x941fffff]: no compatible bridge window >> bart kernel: pci 0000:b1:03.0: can't claim BAR 7 [io 0x0000-0x0fff]: no compatible bridge window >> bart kernel: pci 0000:b1:03.0: can't claim BAR 8 [mem 0x95800000-0x959fffff]: no compatible bridge window >> >> and so on. The final IO memory assignment is the same, though, >> before and after your patch. >> >> 95800000-95bfffff : PCI Bus 0000:b0 >> 95800000-959fffff : PCI Bus 0000:b1 >> 95800000-959fffff : PCI Bus 0000:b2 >> 95a00000-95a3ffff : 0000:b0:00.0 >> >> >> Does that have any relevance or is it just nuisance messages ? > > Yes, I knew this could happen. It should be just nuisance messages, > since we are claming bridge resources even on systems where they > are reassigned. We should remove those messages, this means that I > have to craft a function that claims resources without spitting too > much unwanted noise, I can't use pci_claim_bridge_resource for this > purpose as you have noticed, unless I refactor it, open to suggestions > (we claim bridge resources by default, regardless of PROBE_ONLY flag). > > Thanks a lot for testing it, appreciated, I will prepare a v3. > Hi Lorenzo, There is no need for v3 because of this. My patch set addresses the BAR 7 message, and the BAR 8 message is actually warranted since the memory window on the upstream port is too small. Guenter