linux-kernel - Re: [PATCH v8 3/9] pci: Introduce pci_register_io

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Date:	Wed, 9 Jul 2014 10:13:20 +0100
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci <linux-pci@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 3/9] pci: Introduce pci_register_io_range() helper
 function.

On Wed, Jul 09, 2014 at 07:32:37AM +0100, Arnd Bergmann wrote:
> On Wednesday 09 July 2014, Liviu Dudau wrote:
> > > Maybe that assumption is guaranteed by OF, but it doesn't hold for ACPI;
> > > ACPI can describe several I/O port apertures for a single bridge, each
> > > associated with a different CPU physical memory region.
> > 
> > That is actually a good catch, I've completely missed the fact that
> > io_range->pci_addr could be non-zero.
> 
> Hmm, that's what I thought in my initial review, but you convinced me
> that it's actually correct later on, and I still believe it is. Maybe
> now you got confused by your own code?

Man, it has been too long. Yes, I am now confused by my own code, which
is not a good sign.

> 
> Please have another look, I think your code in pci_host_bridge_of_get_ranges
> sufficiently handles the registration to the PCI code with the correct
> io_offset. The only thing that we might want to add is to record the
> PCI address along with the bridge->io_base: For the host driver to
> set up the mapping window correctly, you either need both of them, or
> you assume they are already set up.

Hmm, having another look at pci_host_bridge_of_get_range() I'm not convinced
that we need another storage for pci_addr. The resource gets added to the
list of resources used by the bridge offsetted by range.pci_addr, so when
re-creating the PCI bus address the value should come in play.

I will double check but I think the code is correct as it is. Sorry for the
early confusion.

Best regards,
Liviu

> 
> 	Arnd
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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