linux-kernel - Re: [PATCH v11 08/10] OF: PCI: Add support for parsing PCI host bridge resources from DT

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Message-ID: <CAL_JsqK3yH-uf++haBovWdX6er1PtzeiZ-2-yT1TRfYPxAjFow@mail.gmail.com>
Date:	Tue, 23 Sep 2014 08:30:08 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Robert Richter <rric@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Tanmay Inamdar <tinamdar@....com>,
	linux-arch <linux-arch@...r.kernel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Jingoo Han <jg1.han@...sung.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Sinan Kaya <okaya@...eaurora.org>,
	Sunil Goutham <sunil.goutham@...iumnetworks.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>
Subject: Re: [PATCH v11 08/10] OF: PCI: Add support for parsing PCI host
 bridge resources from DT

On Tue, Sep 23, 2014 at 2:56 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Monday 22 September 2014 12:43:17 Liviu Dudau wrote:
>> >
>> > From e798af4fc2f664d1aff7e863489b8298f90e716e Mon Sep 17 00:00:00 2001
>> > From: Robert Richter <rrichter@...ium.com>
>> > Date: Mon, 22 Sep 2014 10:46:01 +0200
>> > Subject: [PATCH] OF: PCI: Fix creation of mem-mapped pci host bridges
>> >
>> > The pci host bridge was not created if io_base was not set when
>> > calling of_pci_get_host_bridge_resources(). This is esp. the case for
>> > mem-mapped io (IORESOURCE_MEM). This patch fixes this. Function
>> > parameter io_base is optional now.
>>
>> I think the message is misleading. What you want to do is make io_base
>> optional for the case where the PCI host bridge only expects to have only
>> IORESOURCE_MEM ranges and doesn't care about IORESOURCE_IO ones.
>>
>> As I'm going to touch this area again to address a comment from Bjorn,
>> do you mind if I roll this patch into mine with your Signed-off-by and
>> the mention that you have made io_base optional?
>
> I think the best way to deal with this is to move the check for
> io_base down into the place where it is used: As long as the DT only
> specifies IORESOURCE_MEM windows, we don't need to look at io_base,
> but if the host controller driver does not support IORESOURCE_IO
> while the DT specifies it, I guess it would be nice to return an
> error.

The DT may specify it, but the h/w could be broken in some way so the
host driver chooses to ignore it. I don't think we should force the
host driver to provide a pointer in that case. Also, would we want it
added to the resource list if it is not going to be used?

Rob
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