From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yijing Wang <wangyijing@huawei.com>
Subject: Re: [PATCH v10 07/10] OF: Introduce helper function for getting PCI
 domain_nr
Date: Wed, 10 Sep 2014 09:55:48 +0800
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To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>, linux-pci <linux-pci@vger.kernel.org>, Linus Walleij <linus.walleij@linaro.org>, Liviu Dudau <Liviu.Dudau@arm.com>, Grant Likely <grant.likely@secretlab.ca>, Tanmay Inamdar <tinamdar@apm.com>, linux-arch <linux-arch@vger.kernel.org>, Kukjin Kim <kgene.kim@samsung.com>, Russell King <linux@arm.linux.org.uk>, Jingoo Han <jg1.han@samsung.com>, Jason Gunthorpe <jgunthorpe@obsidianresearch.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, "grant.likely@linaro.org" <grant.likely@linaro.org>, Device Tree ML <devicetree@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>, Will Deacon <Will.Deacon@arm.com>, Rob Herring <robh+dt@kernel.org>, LAKML <linux-arm-kernel@lists.infradead.org>, Sinan Kaya <okaya@codeaurora.org>, LKML <linux-kernel@vger.kernel.org>, Suravee Suthikulanit <suravee.suthikulpanit@amd.com>
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>> OK. Sorry, I have one last question, because domain will be used to calculate the address used to
>> access PCI hardware config registers. So if DTS file doesn't report the domain, how do we know
>> we would access the right registers when we use the auto increment domain vaule ?
>> Has there a mechanism to make sure system can access the correct registers by the domain ?
> 
> I think you're referring to config access via ECAM (PCIe r3.0, sec
> 7.2.2).  In that case, I don't think the domain should be used to
> compute the memory-mapped configuration address.  Each host bridge is
> in exactly one domain, and each host bridge has an associated ECAM
> area base.  The address calculation uses the bus number, device
> number, function number, and register number to compute an offset into
> the ECAM area.
> 
> So as long as the DT tells you the ECAM information for each host
> bridge, that should be sufficient.  The domain number is then just a
> Linux convenience and is not tied to the platform as it is on ia64.

Hi Bjorn, you are right, thanks for your detailed explanation! :)

Thanks!
Yijing.

> 
> Bjorn
> 
> .
> 


-- 
Thanks!
Yijing