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

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Date:	Wed, 02 Jul 2014 14:30:31 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Liviu Dudau <liviu@...au.co.uk>, Sinan Kaya <okaya@...eaurora.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Tanmay Inamdar <tinamdar@....com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v8 3/9] pci: Introduce pci_register_io_range() helper function.

On Tuesday 01 July 2014 21:45:09 Liviu Dudau wrote:
> On Tue, Jul 01, 2014 at 09:36:10PM +0200, Arnd Bergmann wrote:
> > On Tuesday 01 July 2014 19:43:28 Liviu Dudau wrote:
> > 
> > This still conflicts with the other allocator you have in patch 9
> > for pci_remap_iospace: nothing guarantees that the mapping is the
> > same for both.
> > 
> > Also, this is a completely pointless exercise at this moment, because
> > nobody cares about the result of pci_address_to_pio on architectures
> > that don't already provide this function. If we ever get a proper
> > Open Firmware implementation that wants to put hardcoded PCI devices
> > into DT, we can add an implementation, but for now this seems overkill.
> > 
> > The allocator in pci_register_io_range seems reasonable, why not merge
> > this function with pci_remap_iospace() as I have asked you multiple
> > times before? Just make it return the io_offset so the caller can
> > put that into the PCI host resources.
> 
> Hi Arnd,
> 
> While I agree with you that at some moment the allocators were inconsistent
> wrt each other, for this version I would respectfully disagree on this.
> The allocator in pci_register_io_range() only makes sure that the ranges
> are not overlapping, it doesn't do any mapping whatsoever, while
> pci_remap_iospace() does only an ioremap_page_range(). The idea is that
> you get the offset out of pci_address_to_pio() and apply it to
> pci_remap_iospace().

Ok, got it now, I'm sorry I didn't read this properly at first.

Your solution looks correct to me, just using different
tradeoffs to what I was expecting: You get a working pci_address_to_pio()
function, which is probably never needed, but in turn you need to
keep the state of each host bridge in a global list.

	Arnd
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