From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org ([63.228.1.57]:46391 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932669AbbFWXPJ (ORCPT ); Tue, 23 Jun 2015 19:15:09 -0400 Message-ID: <1435101283.3996.17.camel@kernel.crashing.org> Subject: Re: [PATCH] PCI: Only enable IO window if supported From: Benjamin Herrenschmidt To: Bjorn Helgaas Cc: Lorenzo Pieralisi , Guenter Roeck , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "suravee.suthikulpanit@amd.com" , Will Deacon Date: Wed, 24 Jun 2015 09:14:43 +1000 In-Reply-To: References: <1432342336-25832-1-git-send-email-linux@roeck-us.net> <20150527210447.GY32152@google.com> <20150602145510.GE23650@red-moon> <1435099588.3996.14.camel@kernel.crashing.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, 2015-06-23 at 18:02 -0500, Bjorn Helgaas wrote: > On Tue, Jun 23, 2015 at 5:46 PM, Benjamin Herrenschmidt > wrote: > > On Tue, 2015-06-02 at 15:55 +0100, Lorenzo Pieralisi wrote: > >> While at it, do you think it is reasonable to also claim the bridge > >> windows (resources) in the respective pci_read_bridge_* calls ? > > > > No, don't claim in read. There's a clear distinction between gathering > > resources and claiming them, and we need to keep that. > > > > Some fixups might happen in between the two for example. > > Are there any existing fixups like that? Concrete examples would help > figure out the best way forward. Not off the top of my mind, it's been a long time since I wrote the resource claiming stuff in arch/powerpc but it does make me nervous. We collect resources when probing and we claim in the survey, those have been historically very distinct steps. > Most arches call pci_read_bridge_bases() from pcibios_fixup_bus(). I > think that's a poor place to do it because it's code that normally > doesn't have to be arch-specific. Resource claiming is also usually > done from arch code, and it shouldn't be arch-specific either. Claiming as in putting in the resource tree etc... is different from actually reading the values from the HW and is traditionally done much later, no ? > If we move both the read and claim into generic code, then we might > need to make sure there's a fixup phase in between or something. Well, then there's a more general argument to be made as to whether we want the claiming to be "merged" as part of the probing/reading I suppose... Then there's also the case where everything gets fully reassigned, like powernv, where the "read" phase is really only about sizing device BARs... Cheers, Ben.