linux-kernel - Re: [PATCH] arm64: Define HAVE_ARCH_PIO

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Date:	Tue, 14 Jul 2015 09:12:57 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Will Deacon <will.deacon@....com>
CC:	David Daney <ddaney.cavm@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Robert Richter <rrichter@...ium.com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH] arm64: Define HAVE_ARCH_PIO_SIZE and related symbols.

On 07/14/2015 04:00 AM, Will Deacon wrote:
> On Mon, Jul 13, 2015 at 10:31:36PM +0100, David Daney wrote:
>> From: David Daney <david.daney@...ium.com>
>>
>> Needed to make pci_iomap() work.
>
> Care to elaborate?
>

I should have explained what I am doing here a little better.

Systems based on the Cavium ThunderX processor may have up to 8 
independent PCIe root complexes.  The I/O space on each bus occupies an 
independent physical address window.

So, in order to be able to map all of these (semi) contiguously, we need 
a lot more virtual address space than is supplied by the default values 
for all these constants.

The option I chose here was to unconditionally expand the I/O ranges for 
all arm64 systems.  If you think this breaks existing systems/drivers, I 
will have to look for other options.

David Daney

> AFAICT, mapping an IO bar on arm64 just gives you back a VA into our
> PCI_IOBASE region and the ioreadX accessors will just call the readX
> macros, so there should be no need for further port adjustment.
>
> Will
>

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