Subject: Re: [PATCH V6 05/13] acpi, pci: Support IO resources when parsing PCI
 host bridge resources.
To: Bjorn Helgaas <helgaas@kernel.org>, Tomasz Nowicki <tn@semihalf.com>
References: <1460740008-19489-1-git-send-email-tn@semihalf.com>
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 <20160427023916.GF6789@localhost>
Cc: arnd@arndb.de, will.deacon@arm.com, catalin.marinas@arm.com,
        rafael@kernel.org, hanjun.guo@linaro.org, Lorenzo.Pieralisi@arm.com,
        okaya@codeaurora.org, jiang.liu@linux.intel.com, jchandra@broadcom.com,
        robert.richter@caviumnetworks.com, mw@semihalf.com,
        Liviu.Dudau@arm.com, ddaney@caviumnetworks.com, wangyijing@huawei.com,
        Suravee.Suthikulpanit@amd.com, msalter@redhat.com,
        linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        linaro-acpi@lists.linaro.org
From: Jon Masters <jcm@redhat.com>
Message-ID: <57204FDB.6010202@redhat.com>
Date: Wed, 27 Apr 2016 01:36:27 -0400
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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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