linux-kernel - Re: [PATCH V6 05/13] acpi, pci: Support IO resources when parsing PCI host bridge resources.

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Date:	Wed, 27 Apr 2016 01:36:27 -0400
From:	Jon Masters <jcm@...hat.com>
To:	Bjorn Helgaas <helgaas@...nel.org>,
	Tomasz Nowicki <tn@...ihalf.com>
Cc:	arnd@...db.de, will.deacon@....com, catalin.marinas@....com,
	rafael@...nel.org, hanjun.guo@...aro.org,
	Lorenzo.Pieralisi@....com, okaya@...eaurora.org,
	jiang.liu@...ux.intel.com, jchandra@...adcom.com,
	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, ddaney@...iumnetworks.com,
	wangyijing@...wei.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org
Subject: Re: [PATCH V6 05/13] acpi, pci: Support IO resources when parsing PCI
 host bridge resources.

On 04/26/2016 10:39 PM, Bjorn Helgaas wrote:
> On Fri, Apr 15, 2016 at 07:06:40PM +0200, Tomasz Nowicki wrote:
>> Platforms that have memory mapped IO port (such as ARM64) need special
>> handling for PCI I/O resources. For host bridge's resource probing case
>> these resources need to be fixed up with pci_register_io_range/pci_remap_iospace etc.
> 
> ia64 also has memory-mapped I/O port space.

The specific references of interest to anyone here are:

*). Volume 2, Part 1: Itanium® Architecture-based Operating System
Interaction Model with IA-32 Applications 2:267 section "10.7 I/O Port
Space Model" which describes how they can map 4 "legacy" IO ports on a
virtual page when operating in a "sparse" mode.

*). Page 378 of the ACPI6.1 specification Table 6-213 I/O Resource Flag
(Resource Type = 1) Definitions describes how a "sparse" translation can
exist depending upon bit _TRS. This seems to be implemented in Linux
using the ACPI_SPARSE_TRANSLATION types.

> It would be ideal to find
> some way to handle ia64 and ARM64 similarly.  At the very least, we
> have to make sure that this doesn't break ia64.  The ia64 dense/sparse
> I/O spaces complicate things; I don't know if ARM64 has something
> similar or not.

There's nothing directly similar - it's just regular MMIO.

Jon.

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