From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754006Ab2EAG2C (ORCPT ); Tue, 1 May 2012 02:28:02 -0400 Received: from mail-pz0-f51.google.com ([209.85.210.51]:40134 "EHLO mail-pz0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753051Ab2EAG16 convert rfc822-to-8bit (ORCPT ); Tue, 1 May 2012 02:27:58 -0400 MIME-Version: 1.0 In-Reply-To: References: <1332135781-13695-1-git-send-email-yinghai@kernel.org> <1332135781-13695-5-git-send-email-yinghai@kernel.org> Date: Mon, 30 Apr 2012 23:27:58 -0700 X-Google-Sender-Auth: 7YYcFSUIlOROl4pBH23hQti3ZQA Message-ID: Subject: Re: [PATCH -v11 04/30] PCI: Add busn_res into struct pci_bus. From: Yinghai Lu To: Bjorn Helgaas Cc: Jesse Barnes , Benjamin Herrenschmidt , Tony Luck , David Miller , x86 , Dominik Brodowski , Andrew Morton , Linus Torvalds , Greg Kroah-Hartman , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 30, 2012 at 9:02 PM, Bjorn Helgaas wrote: > On Mon, Apr 30, 2012 at 6:32 PM, Yinghai Lu wrote: >> On Mon, Apr 30, 2012 at 4:25 PM, Bjorn Helgaas wrote: >>>> --- a/include/linux/pci.h >>>> +++ b/include/linux/pci.h >>>> @@ -419,6 +419,7 @@ struct pci_bus { >>>>        struct list_head slots;         /* list of slots on this bus */ >>>>        struct resource *resource[PCI_BRIDGE_RESOURCE_NUM]; >>>>        struct list_head resources;     /* address space routed to this bus */ >>>> +       struct resource busn_res;       /* track registered bus num range */ >>>> >>>>        struct pci_ops  *ops;           /* configuration access functions */ >>>>        void            *sysdata;       /* hook for sys-specific extension */ >>> >>> struct pci_bus already includes "secondary" and "subordinate".    This >>> new "busn_res" looks like it will contain the same information.  Why >>> do we need both? >> >> In some case the could be different. >> for root bus from _CRS, busn_res could bigger than subordinate, >> because scan_childbus will update subordinate. > > For a bus below a P2P bridge, I think it's always the case that the > bridge's Subordinate Bus Number in config space == bus->subordinate == > bus->busn_res.end (correct me if I'm wrong).  I don't like the > redundancy in this case. there are about 70 bus->subordinate reference and 40 bus->secondary reference. could try to update them in following patch set. > > For a root bus where you set bus->busn_res from _CRS and > bus->subordinate = pci_scan_child_bus(), bus->busn_res.end will > generally be different from bus->subordinate, but there's no point in > keeping track of bus->subordinate. > > The reason we care about secondary and subordinate is so we can > allocate bus numbers when enumerating devices behind a bridge.  The > only thing we need for that is the aperture of the upstream bridge and > the apertures of any peer bridges on the same bus.  Let's say we have > this: > >        pci 00:00.0 bridge to [bus a-b] >        pci a:01.0 bridge to [bus c-d]  (already enumerated) >        pci a:02.0 bridge to [bus e-f]  (already enumerated) >        pci a:03.0 bridge to [bus x-y]  (enumerating now) > > We know [c-d] is contained in [a-b]; [e-f] is contained in [a-b]; a < > c; and a < e.  To enumerate behind a:03.0, we need to assign x & y > such that a < x; [x-y] is contained in [a-b]; and [x-y] does not > overlap [c-d] or [e-f].  The value from pci_scan_child_bus() is > probably useful for setting y, but we don't have to save it in the > struct pci_bus for that. busn alloc will try to solve x-y may need big range than [a,b], it will extend top of b and parents of bus a. instead of just b+1 blindly. and will have more strict checking to avoid overlapping. > >> and also we have one resource to insert it into the resource tree, so >> later could probe/allocate bus num range. > > Sorry, I didn't understand this. Using busn_res to track and allocate busn range, by put them in the resource tree could reuse resource allocating code. Yinghai